International Space Olympiad 2023 Preliminary Level Reference Book Senior Category [2023, 2023 ed.]

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International Space Olympiad 2023 Preliminary Level Reference Book Senior Category [2023, 2023 ed.]

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1. Name the brightest star in the constellation of Aquila and the twelfth-brightest star in the night sky. A. Vega B. Delta Aquilae C. Altair D. Eta Aquilae Ans: C 2. What is the density of Mercury? A. 5.24 g/cm3 B. 5.43 g/cm³ C. 1.33 g/cm3 D. 3.93 g/cm3 Ans: B 3. What is the calculated duration of WR 93b to explode as a supernova? A. 6,000 years B. 7,000 years C. 8,000 years D. 9,000 years Ans: C 4. Approximately how many galaxies were estimated in 2021 from the data of NASA’s New Horizons space probe? A. 50 billion galaxies B. 100 billion galaxies C. 200 billion galaxies D. 500 billion galaxies Ans: C 5. The H-R Diagram shows that main sequence stars ________. A. Increase in brightness as they decrease in temperature B. Decrease in brightness as they increase in temperature C. Increase in brightness as they increase in temperature D. Decrease in brightness as the decrease in temperature Ans: C 6. An object which produces high energy and is very distant from earth is the ________. A. Globular cluster

B. Open cluster C. Nebula D. Quasar Ans: D 7. Elliptical galaxies make up approximately _______ percentage of galaxies in the Virgo Supercluster. A. 5 -10% B. 10 -15% C. 15 -20% D. 20 -25% Ans: B 8. Largest-known globular cluster in the Milky Way ________. A. Pleiades B. Antares C. Tau Ceti D. Omega centauri Ans: D 9. A blue dwarf is a predicted class of star that develops from a ______ after it has exhausted much of its hydrogen fuel supply. A. Brown dwarfs B. White dwarf C. Red dwarf D. Blue dwarfs Ans: C 10. How many neutron stars are thought to be in the Milky Way? A. 0.5 billion neutron stars B. 1 billion neutron stars C. 2 billion neutron stars D. 5 billion neutron stars Ans: B 11. The first stage of life cycle of a star is ball of gas and ________. A. Heat B. Light C. Gas

D. Dust Ans: D 12. Approximately what percentage of all stars are red dwarfs in the Milky Way? A. 25% B. 40% C. 55% D. 75% Ans: D 13. What makes up most of the mass of the Milky Way galaxy? A. Stars B. Stellar nebula C. Dark matter D. Supermassive blackholes Ans: C 14. Neutron stars are the result of ________. A. Collapsing nebulas B. Red dwarf expansion C. Protons and electrons combining D. Neutrons emitting from a white dwarf Ans: C 15. What is the heaviest element that can be created inside a star? A. Silver B. Iron C. Carbon D. Gold Ans: B 16. How can the presence of a black hole be inferred? A. Through its interaction with surrounding matter B. By looking at the light emitted C. By the star birth ratio of a galaxy D. Absence of infrared in the surrounding matter Ans: A 17. Once Sun has used up all of the hydrogen it will become ________.

A. B. C. D. Ans: C

Red giant Neutron star White dwarf Black hole

18. When the sun is in last stage of stellar evolution it causes its central parts to ________. A. Scatter in space B. Collapse inward C. Flicker D. React Ans: B 19. In Hertzsprung–Russell diagram color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its ________. A. Temperature B. Size C. Location D. None of these Ans: A 20. What is the smallest and coolest kind of star on the main sequence? A. Red dwarf B. Brown dwarfs C. White dwarf D. Blue dwarfs Ans: A 21. A star with a temperature above 30,000 K are called as _________. A. Blue giant B. Main sequence C. White dwarf D. Red giants Ans: B 22. What is the radius of Earth? A. 24,622 km B. 5,598 km C. 6,371 km

D. 11,514 km Ans: C 23. A massive star that has collapsed to such a small volume that its gravity prevents the escape of everything including light. A. Black Hole B. Red giant C. Supernova D. White dwarf Ans: A 24. Mercury's outer shell (crust and mantle) is estimated to be ______ thick. A. 100 km B. 200 km C. 300 km D. 400 km Ans: D 25. _______ are large groups of smaller galaxy clusters or galaxy groups and are among the largest known structures of the cosmos. A. Globular cluster B. Open cluster C. Galactic clusters D. Superclusters Ans: D 26. What is the length of a day on Venus? A. 0d 9h 56m B. 58d 0h 30m C. 167d 10h 0m D. 243d 0h 0m Ans: D 27. Which stars do we always see during the year? Stars ________. A. On the horizon B. Over the north poles in celestial sphere C. In the larger constellations D. Inside other galaxies Ans: B

28. What is the surface area of Jupiter? A. 61.42 billion km² B. 7.618 million km² C. 72.24 billion km² D. 16.42 million km² Ans: A 29. A G-type main-sequence star is also known as ________. A. Orange dwarf B. Blue supergiant C. Red dwarf D. Yellow dwarf Ans: D 30. Mercury takes ______ to make one full rotation. A. 37 Earth days B. 59 Earth days C. 73 Earth days D. 95 Earth days Ans: B 31. The position of Polaris cannot be used to find ________. A. The direction of north B. The latitude C. The time D. The little dipper Ans: C 32. What is the radius of Saturn? A. 53,453 km B. 54,957 km C. 57,756 km D. 58,232 km Ans: D 33. A K-type main sequence star is also known as _________. A. Blue star B. Yellow dwarf

C. Orange dwarf D. Blue supergiant Ans: C 34. M dwarfs are also known as ________. A. Red dwarf B. White dwarf C. Red giant D. Yellow dwarf Ans: A 35. For a standard H-R diagram, what are the stars in the lower left region of the diagram? A. Main sequence stars B. Supergiant C. Giants D. White dwarfs Ans: D 36. What is the orbital period of Mars? A. 687 days B. 786 days C. 29 years D. 47 years Ans: A 37. How do white dwarfs compare with supergiants, in terms of temperature and luminosity? A. White dwarfs are cooler and have higher luminosity than supergiant B. White dwarfs are cooler and have lower luminosity than supergiant C. White dwarfs are warmer and have higher luminosity than supergiant D. White dwarfs are warmer and have lower luminosity than supergiant Ans: D 38. Mercury's orbit is inclined by ________ to the plane of Earth's orbit (the ecliptic), the largest of all eight known solar planets. A. 4 degrees B. 7 degrees C. 9 degrees D. None of these Ans: B

39. What is the actual brightness of a star called? A. Absolute magnitude B. Luminosity C. Brightness D. Apparent magnitude Ans: D 40. What is the surface area of Earth? A. 61 billion km² B. 8 billion km² C. 510 million km² D. 144 million km² Ans: C 41. ________ is a type of interstellar cloud that is so dense it obscures the light from objects behind it, such as background stars and emission or reflection nebulae. A. Dark nebula B. Emission nebulae C. Reflection nebulae D. Planetary nebulae Ans: A 42. Approximately, what is the radius of Uranus? A. 20,920 km B. 25,362 km C. 30,146 km D. 35,748 km Ans: B 43. How many globular clusters have been identified in the Andromeda galaxy? A. 580 B. 270 C. 460 D. 320 Ans: C 44. The Saturn rings were first observed by ______. A. Copernicus

B. Newton C. Galileo D. None of these Ans: C 45. What is the name given to the hypothetical brown dwarf believed to orbit our Sun? A. Degenerate dwarf B. Red-clump C. Nemesis D. K stars Ans: C 46. The planets are kept in motion in their respective orbits by ________. A. Their great size and spherical shape B. The rotation and density C. Gravitation and centrifugal force D. Rotation of the sun on its axis Ans: C 47. What is the generic name of the largest type of black holes? A. Large Massive Black hole B. Macro Black hole C. Supermassive Black hole D. Supergiant Black hole Ans: C 48. The planet having fourteen moons is ________. A. Venus B. Mars C. Uranus D. Neptune Ans: D 49. Brown dwarfs emit most of their radiation as which kind of radiation? A. Ultraviolet radiation B. Infrared radiation C. Cosmic ray D. Radio Waves Ans: B

50. Brown dwarfs are not considered true stars because they don't fuse ________. A. Hydrogen B. Silicon C. Lithium D. Beryllium Ans: A 51. The youngest known supernova remnant in our galaxy is ________. A. HBH 3 B. G1.9+0.3 C. Cassiopeia A D. SN 1987A Ans: B 52. Which of the following is the largest of the inner planets? A. Venus B. Mercury C. Mars D. Earth Ans: D 53. Globular clusters can have which type of pulsars? A. Radio pulsar B. Magnetar pulsar C. Crab pulsar D. Millisecond pulsar Ans: D 54. ‘The length of its day and the tilt of its axis are almost identical to those of the Earth’. This is true for which planet? A. Uranus B. Neptune C. Saturn D. Mars Ans: D 55. What is considered as the major source of galactic cosmic rays? A. Pulsar wind nebula

B. Supernova C. Star explosion D. Red giant Ans: B 56. Stars are born in ______. A. Black holes B. Protoplanetary disks C. Planetary Nebulae D. The big bang Ans: C 57. How many moons does Jupiter have? A. 67 B. 85 C. 80 D. 51 Ans: C 58. Which is the most recent supernova to have been unquestionably observed by the naked eye in our own galaxy? A. SN 1572 B. SN 1054 C. SN 1885A D. SN 1604 Ans: D 59. A star’s luminosity is a measure of how _______ the star is. A. Hot B. Big C. Bright D. Massive Ans: C 60. How many moons does Uranus have? A. 0 B. 18 C. 27 D. 49

Ans: C 61. Who discovered the first known periodic variable star (as opposed to cataclysmic variables, such as nova and supernovas), Mira, in August 1596? A. Jocelyn Bell B. John Michell C. David Fabricius D. Gustav Kirchhoff Ans: C 62. After a supernova, the core can collapse into a neutron star or if massive enough it can become A. Black dwarf B. Red Supergiant C. Blackhole D. White dwarf Ans: C 63. What is the orbital period of Uranus? A. 74 years B. 84 years C. 94 years D. None of these Ans: B 64. What is the accepted value of the Chandrasekhar limit? (M☉ denotes solar mass) A. 1.4 M☉ B. 1.3 M☉ C. 1.2 M☉ D. 1.5 M☉ Ans: A 65. When did Edwin Hubble invent the Hubble sequence? A. 1892 B. 1914 C. 1926 D. 1938 Ans: C 66. How much the Milky Way is thick at the spiral arms?

A. B. C. D. Ans: B

2257 light years 1000 light years 6000 light years 48000 light years

67. Who discovered the closest brown dwarf system? A. Kevin Luhman B. Edward Luhman C. Richard Luhman D. John Luhman Ans: A 68. Earth takes 365 ¼ days to orbit the Sun. Which of the following is a result of this fact? A. All calendars have 365 days B. February has 28 days instead of 30 C. An extra day is added every four years D. Some holidays are on different dates each year Ans: C 69. As a star like the Sun evolves into a red giant, its core ________. A. Expands and cools B. Contracts and heats C. Expands and heats D. Turns into iron Ans: B 70. What keeps the Earth in its orbit? A. The Sun’s speed rotating B. The Sun’s gravitational pull C. The Earth’s spin direction D. The Earth’s location between other planets Ans: B 71. When astronomers look at distant galaxies, what sort of motion do they see? A. The galaxies are all spinning rapidly B. The galaxies are all moving rapidly toward us C. The galaxies are all moving rapidly away from us D. None of these

Ans: C 72. The closest known neutron star is _________ away Earth. A. 400 light years B. 4,000 light years C. 20 light years D. 1000 light years Ans: A 73. Who took the first photograph of Andromeda? A. Hiroshi Araki B. Isaac Roberts C. Asada Goryu D. David Axon Ans: B 74. Who was awarded the Nobel prize in physics for blackhole science in 2020? A. Andrea M Ghez B. Reinhard Genzel C. Roger Penrose D. All of these Ans: D 75. When standing on the Earth, the Moon and Sun appear to rise in the east and set in the west. What is responsible for this apparent movement of the Sun and Moon? A. The Earth revolves around the Sun B. The Earth rotates on its axis C. The Moon and Sun rotate on their axis D. The Sun and Moon move from east to west in Space Ans: B 76. Disks form around young stars ________. A. If the cloud from which the star forms is too massive for all of it to fall into the star B. When the new star passes through a dense cloud and it is attracted to the star C. From material that was spinning around the protostellar core too fast to fall into the star D. When a second star that formed in orbit breaks up Ans: C

77. The rocks that enter the earth's atmosphere and blaze a trail all the way to the ground and do not burn up completely are known as ________. A. Meteorites B. Meteors C. Asteroids D. None of these Ans: A 78. The stars forming a recognizable shape are called _________. A. Constellation B. System C. Galaxy D. Asteroids Ans: A 79. What happens when a White Dwarf burns out? A. It becomes a Black Dwarf B. It becomes a Red Giant C. It becomes a Blue Giant D. It becomes a Black hole Ans: A 80. Star formation is often aided by ________. A. Planets passing through a molecular cloud and upsetting its equilibrium B. A gravitational vibration caused by thermal instability in interstellar gas C. A supernova explosion near a molecular cloud that compresses it and starts fragments collapsing D. Heating of an interstellar cloud by a nearby young star Ans: C 81. The constellations of stars appear at different positions in the sky at different times during night mainly _________. A. Because Earth rotates about its axis B. Because Earth revolves round the Sun C. Because of optical illusion D. Because celestial bodies are changing their positions all the time Ans: A 82. Which of the following is an extremely luminous active galactic nucleus (AGN)?

A. B. C. D. Ans: B

Pulsar Quasar Blackhole White dwarf

83. The mass of Jupiter is almost ________. A. Tenth of the mass of the Sun B. One thousandth of the mass of the Sun C. Hundreds of the mass of the Sun D. Half of the mass of the Sun Ans: B 84. Which among the following was the first comet to be observed by a manned spacecraft? A. Comet Kohoutek B. Halley's Comet C. Comet Borrelly D. Kreutz Sungrazer Ans: A 85. What is the mass of a star that potential of becoming a neutron star when it collapses? A. Above 3 solar masses B. Above 8 solar masses C. Above 24 solar masses D. Above 52 solar masses Ans: B 86. Who discovered the first asteroid Ceres? A. William Herschel B. Giuseppe Piazzi C. Nicolaus Copernicus D. Edwin Hubble Ans: B 87. Typically neutron stars can rotate at up to ________. A. Several hundred times per second B. 500 times per second C. 2 trillion times per second D. 1 billion times per second

Ans: A 88. According to NASA, the current number of known comets is ________. A. 3,743 B. 5,538 C. 1,142 D. 7,346 Ans: A 89. What percentage of known neutron stars are part of a binary system? A. 25% B. 5% C. 10% D. 50% Ans: B 90. Which of the following best describes the surface of Jupiter? A. Cloudy and hot with lots of volcanoes B. Cold, rocky and covered in red dust C. A thick layer of hydrogen gas D. Barren and rocky with lots of craters Ans: C 91. The nearest neutron star is part of a close group of neutron stars called _________. A. The Magnetic Six B. The Pulsating Four C. The Magnificent Seven D. None of these Ans: C 92. Why does the Earth experience seasons? A. The Earth is tilted on its axis B. The Sun is hotter in the Spring and Summer C. The Earth gets less sun in the Fall and Winter D. The distance between the Sun and the Earth changes Ans: A 93. Who detected the cosmic microwave background radiation for the first time? A. Robert Wilson

B. Arno Penzias C. Max Planck D. Both A and B Ans: D 94. Who of the following discovered the laws of planetary orbits? A. Galileo Galilei B. Nicholas Copernicus C. Johannes Kepler D. Isaac Newton Ans: C 95. Dark energy makes up approximately ________. A. 68% of the universe B. 89 % of the universe C. 95 % of the universe D. 99% of the universe Ans: A 96. Which of the following facts about Elliptical galaxies is true? A. Brighter than spiral galaxies B. Around 30% of all galaxies C. Contain mostly older stars D. Have abundant interstellar matter Ans: C 97. The Magellanic clouds are _______. A. Nebula B. Galaxy C. Supernova remnant D. Star cluster Ans: B 98. An ________ occurs when the two planets lie in a line on the same side of the Sun. A. Inferior conjunction B. Superior conjunction C. Quasiconjunction D. None of these Ans: A

99. Energy is generated in the cores of stars by fusing _________. A. Carbon into helium B. Hydrogen into helium C. Lithium into hydrogen D. Helium into hydrogen Ans: B 100. A type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. A. Spiral shape galaxy B. Irregular shape galaxy C. Elliptical shape galaxy D. Regular shape galaxy Ans: C 101. A cooler class of star was given the letter _______. A. 'O' B. 'L' C. 'F' D. 'M' Ans: D 102. Which scientist discovered that Black holes leak energy? A. John Oppenheimer B. Karl Schwarzschild C. Stephen Hawking D. Julian Huxley Ans: C 103. ________ are incredibly dense and similar to the density of an atomic nucleus. A. Yellow dwarf B. Brown dwarf C. Red giant D. Neutron stars Ans: D 104. Who was the first person to resolve stars in the central region of the Andromeda Galaxy? A. Walter Baade

B. John Baldwin C. William Herschel D. Vesto Slipher Ans: A 105. Name the coldest-known brown dwarf discovered _______. A. WISE 0255−1114 B. WISE 0855−0714 C. WISE 0957−0724 D. WISE 0535−0314 Ans: B 106. The Milky Way is part of which supercluster of galaxies? A. Laniakea B. Caelum C. Shapley D. Pisces-Cetus Ans: A 107. Which element can distinguish candidate brown dwarfs from low-mass stars? A. Sodium B. Oxygen C. Lithium D. Potassium Ans: C 108. What is a galaxy? A. A cloud of interstellar gas and dust at least 10 light years across B. A cluster of stars which contains more than 100 stars C. A star, together with all of its planets and surrounding matter disk D. A collection of millions or billions of stars bound together by gravity Ans: D 109. What can escape a black hole? A. Nothing B. Light C. Particles D. Dust Ans: A

110. Objects more massive than our Sun form into stars ________. A. In about the same time B. Much slower, over billions of years C. Much faster, over tens of thousands of years D. Not at all they are unstable Ans: C 111. When was the nebular hypothesis revised? A. 1796 B. 1900 C. 1950 D. 1920 Ans: A 112. Black holes are _______. A. Dead stars B. Strong nebulas C. Dead planets D. None of these Ans: A 113. Most of the galaxy's diameter (parsecs) ranges from ______. A. 1,000 to 300,000 B. 1,000 to 100,000 C. 1,000 to 200,000 D. 1,000 to 400,000 Ans: B 114. Convection is important in stars because it _______. A. Increases the temperature of the star B. Ionized gas ejected C. Transports energy outward in the star D. Carries the neutrinos to the surface of the star where they can escape Ans: C 115. From which of these our solar system has been formed? A. Nebula B. Dust grains

C. Planetesimal D. None of these Ans: A 116. What is a black hole? A. Comet that has turned black B. Top of a galaxy C. Bottom of a galaxy D. Evolutionary end point of a massive star Ans: D 117. A _______ the time required for a body within the solar system, such as a planet, the Moon, or an artificial Earth satellite, to return to the same or approximately the same position relative to the Sun as seen by an observer on the Earth. A. A conjunction B. An opposition C. A sidereal period D. A synodic period Ans: D 118. Which category of star is the Sun found in on an H-R Diagram? A. Red Giants B. Main Sequence C. Blue Giant D. White Dwarf Ans: B 119. Messier did his observation of astronomical objects by using which telescope? A. 100 mm refracting telescope B. 100 mm reflecting telescope C. 150 mm refracting telescope D. 150 mm reflecting telescope Ans: A 120. Name the first exemplar Class 0 protostar, a type of embedded protostar that has yet to accrete the majority of its mass. A. VLA 1623 B. VLA 1435 C. VLA 1589

D. VLA 1362 Ans: A 121. The Messier number and NGC number of the Andromeda Galaxy are ________. A. Messier 13 and NGC 6205 B. Messier 26 and NGC 6694 C. Messier 31 and NGC 224 D. Messier 44 and NGC 2632 Ans: C 122. How old are the oldest stars? A. 10-15 billion years old B. 20-25 billion years old C. 25-30 billion years old D. A century Ans: A 123. Name the largest galaxy supercluster. A. Caelum Supercluster B. Grus Supercluster C. Columba Supercluster D. Aquarius Supercluster Ans: A 124. Which of the following masses of stars would become a super red giant in their final stages of life? A. 2 M☉ to 10 M☉ B. 8 M☉ to 30 M☉ C. 12 M☉ to 40 M☉ D. 25M☉ to 60 M☉ Ans: B 125. When did the Andromeda galaxy form? A. Roughly 10 billion years ago B. Roughly 12 billion years ago C. Roughly 8 billion years ago D. Roughly 6 billion years ago Ans: A

126. Who developed the Nebular hypothesis theory? A. Pierre Laplace B. Georges Lemaitre C. Immanuel Kant D. Robert Wilson Ans: C 127. Who discovered the existence of superclusters? A. John Baldwin B. William Herschel C. George Abell D. Harlow Shapley Ans: D 128. What type of star is our Sun? A. White dwarf B. Yellow dwarf C. Red dwarf D. None of these Ans: B 129. The core of the Andromeda Galaxy is called _______. A. Sgr A* B. 2C 56 C. PGC 5065047 D. NGC 6720 Ans: B 130. How do stars appear to move? A. From east to west B. From west to east C. From north to south D. From south to north Ans: A 131. What is the approximate diameter of Andromeda Galaxy in kiloparsecs? A. 10.58 B. 17.34 C. 34.67

D. 46.56 Ans: D 132. Knowing the age of a White Dwarf means that astronomers can know the age of the ________. A. Planet B. Universe C. Sun D. Comet Ans: B 133. What is the approximate distance between the Andromeda galaxy from Earth and the nearest large galaxy to the Milky Way? A. 1.5 million light-years B. 2.0 million light-years C. 2.5 million light-years D. 3.0 million light-years Ans: C 134. Where does a star begin and end its life? A. Black Hole B. Galaxy C. Nebula D. Solar System Ans: C 135. What percent of stars in the Milky Way will become White Dwarfs? A. 23% B. 46% C. 74% D. 97% Ans: D 136. Name the first Seyfert galaxy. A. Cygnus A B. Messier 77 C. Whirlpool galaxy D. None of these Ans: B

137. Name the second supercluster found, after the Local Supercluster. A. Shapley Supercluster B. Ophiuchus Supercluster C. Hercules Superclusters D. Coma Supercluster Ans: A 138. The widely accepted modern variant of the nebular theory is the SNDM. Expand SNDM. A. Solar nebular distant model B. Solar nuclear data model C. Solar nebular disk model D. Spatial nebula data modeling Ans: C 139. A rotating black hole is a black hole that possesses ________. A. Angular momentum B. Linear momentum C. Both A and B D. None of these Ans: A 140. An early stage in the formation of a star before nuclear synthesis begins is called a _________. A. Protostar B. Supernova C. Neutron star D. Black hole Ans: A 141. More than two-thirds of all observed galaxies are _________. A. Barred spiral B. Irregular C. Spiral galaxies D. Elliptical Ans: C 142. What leads directly to the formation of black holes? A. Neutron Star B. Planetary nebula

C. Supernova D. Blue giant Ans: C 143. The nearest large galaxy to the Milky way is _______. A. The Sombrero galaxy B. The Galaxy named bob C. The Andromeda galaxy D. The whirlpool galaxy Ans: C 144. On the H-R diagram the white dwarf stars are located where? A. Top right B. Top left C. Bottom left D. Bottom right Ans: C 145. C-type asteroids consists of _______. A. Clay B. Silicate rocks C. Iron D. Both A & B Ans: D 146. After billions of years go by, a white dwarf will cool into a burnt-out cinder. This remnant is known as a(n) _______. A. Brown dwarf B. Dwarf planet C. Black hole D. Black dwarf Ans: D 147. Comet is an object with a ______ head and a _______ tail. A. Pale, long B. Bright, long C. Pale, short D. Bright, short Ans: B

148. A small dense star, about the size of a planet, that forms when a low-mass star runs out of nuclear fuel is called a(n) _______. A. Neutron star B. White dwarf C. Yellow star D. Black hole Ans: B 149. What type of galaxy is the Milky Way? A. Lenticular galaxy B. Spiral galaxy C. Elliptical galaxy D. Irregular galaxy Ans: B 150. Tight group of one million (approx.) Stars which look like a ball is called _______. A. Globular cluster B. Open cluster C. Globular cluster D. Quasar Ans: A 151. Which is the brightest mercury-manganese star known? A. Alpha Andromedae B. Beta Andromedae C. Upsilon Andromedae D. Zeta Andromedae Ans: A 152. LSB galaxies had been first theorized in _______. A. 1967 B. 1954 C. 1969 D. 1976 Ans: D 153. A spectrum of a star is made up of _______. A. Spectrum lines

B. Emission lines C. Coordinate lines D. None of these Ans: B 154. Stars are formed from big clouds of gas and dust is known as _______. A. Space fog B. Neutron clouds C. Nebulae D. Dust Ans: C 155. The Comet tail is made up of the charged particles called _______. A. Electrons B. Protons C. Neutrons D. Plasma Ans: D 156. In the death of a large mass star gravitational collapse is so complete that no energy or matter can escape. This is called a __________. A. Neutron star B. Black dwarf C. Supernova D. Black hole Ans: D 157. When was the last supernova in the Milky Way well observed? A. 1589 B. 1604 C. 1723 D. 1862 Ans: B 158. About 4.5 billion years ago, a cloud of stellar dust or nebula existed within the Milky Way. What happened next? A. The energy enriched nebula begins to contract further due to gravity B. Asteroid collision C. Shock wave from supernova of a nearby star occurs

D. None of these Ans: C 159. The Sagittarius Dwarf Spheroidal Galaxy is also known as _______. A. The Sagittarius Dwarf Elliptical Galaxy B. The Sagittarius Dwarf Spiral Galaxy C. The Sagittarius Dwarf Peculiar Galaxy D. The Sagittarius Dwarf Irregular Galaxy Ans: A 160. Galaxies were initially discovered telescopically and were known as ________. A. Unresolved star clusters B. Anagalactic nebulae C. Spiral nebulae D. None of these Ans: C 161. ________ is sometimes informally referred to as the Pinwheel Galaxy, a nickname it shares with Messier 101. A. Cartwheel Galaxy B. Medusa Merger C. Mice Galaxies D. Triangulum Galaxy Ans: D 162. Most stars are cooler than the sun. These stars, the planets, interstellar clouds and star-forming regions emit most of their radiant energy in the _______. A. Visible B. X-ray region C. Ultraviolet D. Infrared Ans: D 163. Abell 2744 is nicknamed as ________. A. Musket Ball Cluster B. Pandora's Cluster C. Bullet Cluster D. None of these Ans: B

164. A blue shift means a Doppler shift of light from a(an) ________. A. Receding star B. Blue star C. Approaching star D. Fixed star Ans: C 165. A ________ is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star. A. Planetary disk B. Protoplanetary disk C. Galactic disk D. Meteoroid Ans: B 166. Which constellation has Polaris, the North Star? A. Ursa Minor B. Taurus C. Circinus D. Hydra Ans: A 167. Who discovered the first Apollo asteroid? A. Mount Lemmon Survey B. James Whitney Young C. Eleanor F Helin D. Karl Wilhelm Reinmuth Ans: D 168. When fusion in low-mass stars form this element in its core, the helium flash stage begins? A. Carbon B. Helium C. Oxygen D. Hydrogen Ans: A 169. Which is the first Apollo asteroid discovered? A. 1852 Apollo

B. 1862 Apollo C. 1952 Apollo D. 1962 Apollo Ans: B 170. An expanding, glowing shell of gas around an aging star is called ________. A. A planetary nebula B. A planetary nimbus C. A dwarf nebula D. A dwarf nimbus Ans: A 171. Puppis is a constellation in the ________. A. Southern sky B. Northern sky C. None of these Ans: A 172. What is the largest factor that determines the lifespan of a star? A. Distance, the star starts with B. Elements, the star starts with C. Age of star D. Mass of hydrogen, the star starts with Ans: D 173. In astronomy, a _______ is a tightly packed group of stars within a larger star formation. A. Spiral disks B. Galactic bars C. Galactic bulge D. None of these Ans: C 174. What event marked the birth of the Sun? A. Nuclear fusion B. Nuclear Fission C. Light D. Heat Ans: A

175. A big cloud of dust and gas where all stars begin their life cycle is called a _______. A. Solar system B. Universe C. Galaxy D. Nebula Ans: D 176. Which among the following might be a type of luminous blue compact galaxy that is undergoing very high rates of star formation? A. Pea galaxy B. Barnard's Galaxy C. Phoenix Dwarf Galaxy D. Aquarius Dwarf Galaxy Ans: A 177. Which type of star is maintained by the pressure of an electron gas? A. Main Sequence Star B. White Dwarf C. Neutron Star D. Black Hole Ans: B 178. The closest Fossil Group to the Milky Way is ________. A. MS 0302+17 B. NGC 6482 C. Borg-58 D. None of these Ans: B 179. What color of star is the coolest? A. Yellow B. White C. Red D. Blue Ans: C 180. Lota trianguli is a binary star in which constellation? A. Triangulum B. Ursa Major

C. Taurus D. Gemini Ans: A 181. A stellar nebula is made up of ________. A. Clouds of gas B. Planets C. Stars D. Clouds of gas and dust Ans: D 182. Who among the following modified Nebular theory in 1796? A. Laplace B. Neuton C. Kepler D. Ptolemy Ans: A 183. Why do low-mass stars take much longer to reach the main sequence? A. They do not have enough mass to ever produce core fusion B. Because they have less initial material to work with C. Because they do not form in star clusters D. With stars"lower" is equivalent to "slower" Ans: B 184. The _______ is a formulaic prediction of spacing between planets in any given solar system. A. Titius–Bode law B. Planetary Law C. Celestial Law D. None of these Ans: A 185. The Star located vertically above the North pole is _________. A. Polaris B. Aldebaran C. Sirius D. Regel Ans: A

186. The existence of superclusters was first postulated by whom? A. Lewis Boss B. Thomas Bopp C. George Abell D. Alphonse Borrelly Ans: C 187. White dwarfs are so small, they're actually _________. A. Quite bright B. Quite cool C. Quite faint D. Quite hot Ans: C 188. The word galaxy is derived or connected to which language? A. Latin B. Greek C. French D. All of these Ans: D 189. The major steps in the formation of the solar system based on the Nebular Theory are: Cloud collapse, formation of the protoplanetary disk and _________. A. Growth of planets B. Galaxy formation C. Birth of star D. Supernova Ans: A 190. When did GN-z11, the oldest and most distant galaxy observed? A. 2013 B. 2014 C. 2015 D. 2016 Ans: C 191. Main sequence stars are made primarily of which element? A. Hydrogen and Helium B. Carbon and Iron

C. Hydrogen only D. Helium and Carbon Ans: A 192. Brightest stars are represented by apparent magnitude numbers which are ________. A. Negative B. Positive C. Integers D. Prime Ans: A 193. _________ is a main belt asteroid which was discovered on January 9, 1992 by E F Helin and given the provisional designation “1992 AN”. It was later renamed after an American astronomer. A. 9963 Sandage B. 433 Eros C. 4179 Toutatis D. 99942 Apophis Ans: A 194. The apparent magnitude of -26.8 is of _________. A. Sun B. Moon C. Jupiter D. Neptune Ans: A 195. How do stars form? A. Through emission B. Through supernova C. Through the Sun D. When nebula collapses and nuclear fusion occurs Ans: D 196. Which is the measure of brightness of a star which can be seen from Earth? A. Absolute magnitude B. Apparent magnitude C. Light year D. Parallax

Ans: B 197. Stars that never accumulated enough mass for core nuclear fusion to fully occur are _________. A. Known as Hayashi tracked protostars B. Classified as white dwarfs C. Known as brown dwarfs D. None of these Ans: C 198. The first planetary nebula was discovered in 1764 by the French astronomer _________. A. William Herschel B. Charles Messier C. Edwin Hubble D. Harlow Shapley Ans: B 199. A star is ________. A. A star that produces energy steadily due to nuclear fusion B. Several planets close together C. An object with planets orbiting it D. A Nebula that skips a protostar and is instantly turns into a red gaint Ans: A 200. If the Universe is infinite, every line of sight should eventually intersect a star. This is ________. A. Gibb’s Paradox B. Twin’s Paradox C. Obler’s Paradox D. None of these Ans: C 201. Massive protostars stars in nebulae can ________. A. Prevent further massive star formations B. Enhance star formation C. Create black holes D. None of these Ans: A

202. What is the matter and radiation that exist in the space between the star systems in a galaxy? A. Interstellar medium B. Cosmic fluff C. Interstellar void D. None of these Ans: A 203. A protostar is what is formed when a nebula's gas and dust come closer together. A. True B. False Ans: A 204. In astronomy, the term compact star refers to _______. A. White dwarfs B. Neutron stars C. Black holes D. All of these Ans: D 205. A star is a luminous sphere of plasma held by _________. A. Its own gravity B. Dark matter C. Heat D. Vacuum Ans: A 206. Which one of the following type of main sequence stars is the most massive? A. O-type B. F-type C. A-type D. B-type Ans: A 207. The Sun fuses helium into carbon, along with a dash of ________. A. Silicon and neon B. Neon and lithium C. Oxygen and silicon D. Oxygen and neon Ans: D

208. In the southern sky, stars move ________. A. Clockwise B. Counter-clockwise C. Vertically D. None of these Ans: A 209. Once low mass stars (greater than 0.1 M☉) have depleted their core hydrogen they become _________. A. Red giants B. Supergiants C. Protostars D. Black hole Ans: A 210. Which one of the following type of main sequence stars has the least lifetime? A. O-type B. F-type C. A-type D. B-type Ans: A 211. Stars are made up of _______ and ________. A. Fire and ash B. Gas and plasma C. Fire and plasma D. Plasma and liquid Ans: B 212. A planetary nebula is _______. A. Another term for the disk of gas around a young star B. The cloud from which protostars form C. A shell of gas ejected from a star late in its life D. What is left when a white dwarf star explodes as a supernova Ans. C 213. The region at the centre of a black hole where the space-time curvature becomes infinite is called the ______.

A. B. C. D. Ans: C

Event horizon Ergosphere Singularity Luminosity

214. In an H-R Diagram, stars with the smallest radius are found in the _______ of the diagram. A. Upper left corner B. Upper right corner C. Lower left corner D. Lower right corner Ans: C 215. Black holes have which of the following is the correct ste of properties used to describe a blackhole? A. Mass, charge and angular momentum B. Magnetic charge, mass and charge C. Temperature, gravity and mass D. None Ans: A 216. Asteroids are also known as ________. A. Minor planets B. Small stars C. Planets D. Both A & B Ans: A 217. Who formulated the nebular hypothesis? A. Immanual Kant B. Aristotle C. Chamberlain D. Pierre Laplace Ans: A 218. Parsec is the unit of measurement of ________. A. Density of stars B. Astronomical distance C. Brightness of heavenly bodies

D. Orbital velocity of giant stars Ans: B 219. Once helium fusion stops, the dominant force in supporting the core of a star is called ________. A. Neutron degradation pressure B. Photon depravity pressure C. Electron degeneracy pressure D. Proton dissoluteness pressure Ans: C 220. The four largest planets of the solar system in descending order are ________. A. Jupiter, Mercury, Saturn and Uranus B. Mercury, Jupiter, Saturn and Neptune C. Jupiter, Saturn, Uranus and Neptune D. Jupiter, Mercury, Saturn and Neptune Ans: C 221. What are circumpolar stars? A. Stars that can only be seen from the North Pole B. Stars that cannot be seen from the North Pole C. Stars that never set below horizon D. Stars that set belove horizon Ans: C 222. In the H-R diagram, 90 percent of all stars are ________. A. In the giant region B. In the supergiant region C. Among the B stars D. On the main sequence Ans: D 223. Which of the following sequences below correctly describes the evolution of the Sun from young to old? A. White dwarf, red giant, main-sequence, protostar B. Red giant, main-sequence, white dwarf, protostar C. Protostar, red giant, main-sequence, white dwarf D. Protostar, main-sequence, red giant, white dwarf Ans: D

224. What prominent pattern of stars is seen overhead after dark in the late Summer and throughout the fall? A. Orion’s Belt B. The Fall Hexagon C. The Winter Hexagon D. The Summer Triangle Ans: D 225. Jupiter is how many A.U. from the Sun? A. 6.5 A.U B. 6.0 A.U C. 4.9 A.U D. 5.2 A.U Ans: D 226. Name the largest constellation in the sky. A. Virgo B. Orion C. Ursa Major D. Hydra Ans: D 227. Lunar swirls are enigmatic features found across the _______ surface. A. Moon's B. Earth’s C. Mars’s D. None of these Ans: A 228. The size of a black hole is roughly proportional to its mass and determined by ________. A. The radius of the event horizon B. Its angular momentum C. Its electric charge D. Speed Ans: A 229. When a star's visible light passes through interstellar dust, the light we see ________. A. Turn bluish in color

B. Is Doppler shifted C. Ionized the dust and creates emission lines D. Is dimmed and reddened Ans: D 230. Stellar black holes are produced through ________. A. Gravitational collapse B. Extreme temperatures C. Angular momentum spikes D. Centrifugal force Ans: A 231. Who coined the term “Supermoon”? A. Richard Nolle B. Michel Gauquelin C. Shawn Carlson D. None of these Ans. A 232. The star gets denser and hotter, ultimately changing into helium by process of _______. A. Conduction B. Convection C. Nuclear fusion D. Nuclear fission Ans: C 233. One Jupiter day is equal to which of the following? A. 30 hrs 40 min B. 9 hrs 50 min C. 3 hrs 20 min D. 52 hrs 12 min Ans: B 234. The planets of the solar system formed as ________. A. The center of the gas cloud cooled B. Planetesimals flattened into a rotating disk C. Planetesimals collided into one another D. The Sun absorbed extra gas and dust from the solar system Ans: C

235. A black hole without electric charge or angular momentum is called a ________. A. Reissner-Nordstrom black hole B. Kerr black hole C. Schwarzschild black hole D. Supermassive black hole Ans: C 236. The radiant energy of the sun is transmitted in the form of ________. A. Waves B. Particles C. Both A & B D. None of these Ans: A 237. Which of these statements best describes a black hole? A. A small, hot, carbon-oxygen core left over from a massive stars’ death B. An extremely dense mass of neutrons left behind by a collapsing star C. An object with a very slow escape velocity D. A compact object with an escape velocity greater than the speed of light Ans: D 238. Which of the following is indicated by the colour of a star? A. Weight B. Distance C. Temperature D. Size Ans: C 239. A typical galaxy, such as our Milky Way galaxy, contains how many billion stars? Is it approximately ________. A. 10 billion B. 50 billion C. 100 billion D. 200 billion Ans: D 240. Name the satellite of Jupiter which is the largest and most massive of the Solar System's moons.

A. B. C. D. Ans: C

Europa Callisto Ganymede Himalia

241. Which types of stars would it be if you had a spectra rating of between an O and a D? A. Yellow stars and Giant B. Red Dwarf and Blue giant C. Red giant and Main sequence D. Blue Giants and White Dwarfs Ans: D 242. Which planet was named after the Roman God of the Sea? A. Mars B. Jupiter C. Neptune D. Saturn Ans: C 243. Position of a celestial body can be determined by ________. A. Nadir B. Azimuth C. Zenith D. Co-ordinates Ans: D 244. Halley’s comet appears once in a period of ________. A. 24 years B. 32 years C. 76 years D. 84 years Ans: C 245. The ring nebula is an example of a planetary nebula. It is ________. A. A ring of planets circling a star B. An expanding ring of gas released from a dying star C. A contracting ring of gas and dust falling circling into a massive object D. A ring of stars in a circular orbit

Ans: B 246. How many moons does Venus have? A. 0 B. 1 C. 7 D. 3 Ans: A 247. Who introduced the term blackbody? A. Willem Luyten B. Gustav Kirchhoff C. Shiv S Kumar D. Alex Wolszczan Ans: B 248. _______ appears to have a solid silicate crust and mantle overlying a solid, iron sulfide outer core layer, a deeper liquid core layer and a solid inner core. A. Mercury B. Venus C. Jupiter D. Mars Ans: A 249. Many stars are members of groups of two or more stars called ________. A. Galaxies B. Eclipsing binaries C. Multi-star systems D. Star clusters Ans: C 250. Jupiter's upper atmosphere is about _______ by volume. A. 90% hydrogen and 10% helium B. 10% hydrogen and 90% helium C. 70% hydrogen and 30% helium D. 30% hydrogen and 70% helium Ans: A 251. Which comparison is correct?

A. B. C. D. Ans: A

Type O giants may brighter than supergiant Type O giants may just as bright as supergiant Type O giants may not have a brightness None of these

252. _______ was the brightest of six globulars discovered by Turkish-Armenian astronomer Agop Terzan in 1968. A. Minniti 32 B. Palomar 5 C. Segue 3 D. Terzan 7 Ans: D 253. Which instrument is used to analyze the spectrum of stars? A. Camera B. Telescope C. A spectrograph D. None of these Ans: C 254. The solar nebula hypothesis states that which of the following was formed from a nebula? A. The Sun B. The Planets C. The Moon D. All of these Ans: D 255. Which is the first detected multiply-lensed supernova? A. SN 1885A B. MACS J1149 C. Cas A D. SN Refsdal Ans: D 256. Hertzsprung-Russell is a diagram which shows a relationship between star's surface temperature and ________. A. Absolute magnitude B. Size

C. Brightness D. Relative magnitude Ans: A 257. Which constellation is home to Canopus; the second brightest star in the night sky? A. Libra B. Cancer C. Ursa Minor D. Carina Ans: D 258. Earth is an _______ relative to Mars. A. Superior planet B. Inferior planet C. Minor planet D. None of these Ans: B 259. The mass that a spherical cloud of interstellar gas must have in order to contract under its own weight is called _________. A. Jeans mass B. Planck’s mass C. Chandrasekhar limit D. Wein’s mass Ans: A 260. Name the third largest planet in the Solar System. A. Neptune B. Mercury C. Uranus D. Jupiter Ans: C 261. What kind of dwarfs resist gravitational collapse primarily through electron degeneracy pressure? A. Yellow dwarf B. White dwarf C. Black dwarf D. Orange dwarf

Ans: B 262. What is the orbital velocity of Mercury? A. 47.4 km/s B. 13.1 km/s C. 9.7 km/s D. 35.0 km/s Ans: A 263. Black holes do not produce ________. A. Heat B. Light C. Mass emissions D. None of these Ans: B 264. Name the closest rocky exoplanet and closest potentially habitable exoplanet. A. Proxima Centauri b B. Proxima Centauri c C. Alpha Centauri A D. Alpha Centauri B Ans: A 265. What is the temperature of Mercury during daytime? A. 430°C B. 471°C C. -28°C D. -233°C Ans: A 266. The Big Dipper is part of which constellation? A. Ursa Major B. Cassiopeia C. Orion D. Canis Major Ans: A 267. Which physical force dominates the process of star formation? A. Weak nuclear force

B. Electrical force C. Gravitational force D. Reactional force Ans: C 268. How long will it take the Sun to become a black dwarf? A. 2 quadrillion years B. 5000 billion years C. 1 quadrillion years D. 1000 billion years Ans: C 269. Which of these is a dwarf planet? A. Neptune B. Titan C. Eris D. Hydra Ans: C 270. The inner layers of stars are usually _______. A. Lighter B. Denser C. Colder D. Warmer Ans: B 271. The formation of large atomic nuclei from smaller atomic nuclei in the core of stars by nuclear fusion is called _______. A. Gravitational collapse B. Nucleosynthesis C. Nuclear production D. None of these Ans: B 272. Globular cluster M4 is found in the constellation of _______. A. Orion B. Scorpius C. Cassiopeia D. Ursa Major

Ans: B 273. The Planet amongst the following (other than Saturn), that shows a faint ring is ________. A. Earth B. Jupiter C. Mars D. Pluto Ans: B 274. Uranus appears greenish in color due to the presence of _______ in its atmosphere. A. Hydrogen deuteride gas B. Methane gas C. Helium gas D. Hydrogen sulfide gas Ans: B 275. Andromeda Galaxy comes under which morphological classification? A. Elliptical galaxy B. Lenticular galaxy C. Barred Spiral galaxy D. Spiral galaxy Ans: C 276. Name the nearest dwarf galaxy. A. Crater 2 dwarf B. Sculptor Dwarf Irregular Galaxy C. Fornax Dwarf D. Canis Major Dwarf Ans: D 277. How many stars do galaxies have on average? A. 1 million stars B. 10 million stars C. 100 million stars D. 1000 million stars Ans: C 278. When enough mass is accreted by a proto-star then _______ occurs at the core. A. Nuclear fission

B. Chemical reactions C. Nuclear fusion D. None of these Ans: C 279. When does a star reach equilibrium? A. When gravity is balanced by the outward force of nuclear fusion B. When it no longer produces any antimatter C. When the amount of hydrogen equals the amount of helium D. When it reaches the point where nuclear fusion is about to begin Ans: A 280. Messier 1 is a supernova remnant, known as the ________. A. Omega Nebula B. Horsehead Nebula C. Crab Nebula D. Red Rectangle Nebula Ans: C 281. What do most stars originally form as? A. Binary stars or multiple stars B. Protostars C. Neutron stars D. Photon stars Ans: A 282. Very young stars in small cluster of 10-100 members are known as _______. A. OB associations B. Globular clusters C. Molecular cloud complexes D. Aggregates Ans: A 283. What is the mass of Mercury? A. 3.301 × 1023 kg B. 6.42 x 1023 kg C. 8.68 x 1025 kg D. 1.90 x 1027 kg Ans: A

284. Which sort of star is the Sun? A. Red giant B. Supergiant C. Main sequence D. White dwarf Ans: C 285. What temperature does the Cosmic Microwave Background (CMB) radiation have at this time? A. 1.52318±0.00023 K B. 2.72548±0.00057 K C. 3.85413±0.00018 K D. 5.12589±0.00092 K Ans: B 286. An exploding massive star whose explosions are responsible for forming all atoms heavier than iron. A. Supernova B. Big bangs C. Thermonuclear detonation D. Novas Ans: A 287. There is no hydrogen left for nuclear fusion in __________. A. Red giant B. White dwarf C. Arcturus D. Betelgeuse Ans: B 288. The moons Mimas and Enceladus were discovered by __________. A. David Scott B. Jim Lovell C. Roger Chaffee D. William Herschel Ans: D 289. _______ is the only planet of the Solar System that is less dense than water.

A. Mercury B. Mars C. Uranus D. Saturn Ans: D 290. Name the innermost irregular moon of Jupiter, which is not part of a known family. A. Themisto B. Europa C. Callisto D. Thebe Ans: A 291. Which of the following scientist had proven that every planet has an elliptical path? A. Galileo B. Newton C. Copernicus D. Kepler Ans: D 292. The only planet whose period of rotation is longer than the period of revolution around the Sun? A. Mercury B. Jupiter C. Venus D. Neptune Ans: C 293. Lowest mass stars are the __________. A. New B. Oldest C. Proximal D. Pollux Ans: B 294. A star which collapse due to gravity smashing electrons and protons is called a __________. A. Pulstar B. Neutron star C. Proton star

D. Electron star Ans: B 295. What is the temperature of the Epsilon Cygni, multiple star system in the constellation of Cygnus? A. 3,240 K B. 1,598 K C. 4,710 K D. 6,013 K Ans: C 296. M101 OT2015-1 is a contact binary that merged into a single star, in a process known as a luminous red nova (LRN). In which galaxy was it located? A. Andromeeda Galaxy B. Pinwheel Galaxy C. Black Eye Galaxy D. Sombrero Galaxy Ans: B 297. The Milky Way and the Large Magellanic Cloud are predicted to merge in approximately _______ years. A. 4.3 billion B. 2.4 billion C. 1.2 billion D. 3.5 billion Ans: B 298. The Milky Way has a number of satellite galaxies, but the biggest one is the _______. A. Sagittarius Dwarf B. Hercules C. Large Magellanic Cloud D. Ursa Major II Dwarf Ans: C 299. The 'White dwarf' collapse into __________. A. Black Hole B. Black dwarf C. Proton star D. Comet star

Ans: B 300. When was planet Neptune discovered? A. 23 August 1864 B. 23 September 1846 C. 23 October 1872 D. 23 November 1839 Ans: B 301. Who discovered Titania and Oberon, the first two moons of Uranus? Ans: William Herschel 302. During a transit, Venus can be seen from Earth as a small black dot moving across the face of the ______. Ans: Sun 303. On _______, Neptune completed its first full barycentric orbit since its discovery in 1846. Ans: 11 July 2011 304. What is the matter and radiation that exists in the space between the star systems in a galaxy? Ans: Interstellar medium 305. A ______ is a star that pulsates radially, varying in both temperature and diameter to produce brightness changes with a well-defined stable period and amplitude. Ans: Cepheid variable 306.Which class of variable stars includes ‘Cepheid stars’? Ans: Pulsating variables 307. Jupiter has a region of strongly non-dipolar field, known as the _____, near the equator Ans: Great Blue Spot 308. The magnetosphere of Jupiter is responsible for intense episodes of ______ from the planet's polar regions. Ans: Radio emission 309. Name some of the moons of Neptune. Ans: Triton, Hippocamp, Nereid, Proteus, Thalassa, Naiad

310. Neptune's orbit has a profound impact on the region directly beyond it known as the ______. Ans: Kuiper belt 311. Transits of Mercury can only occur when the Earth is aligned with a ______. Ans: Node of Mercury's orbit 312. Titan completes an orbit around ______ once every 15 days 22 hours. Ans: Saturn 313. Saturn's interior is most likely composed of a core of _______. Ans: Iron–nickel and rock 314. The elliptical orbit of Neptune is inclined _______ compared to that of Earth. Ans: 1.77° 315. Saturn is probably best known for the system of ______ that makes it visually unique. Ans: Planetary rings 316. When was the first variable star identified? Ans: In 1638 317. Delta Equulei is the second brightest star in the constellation Equuleus. Delta Equulei is a binary star system about 60 light years away. Who later showed this to be an unrelated optical double star? Ans: Friedrich Georg Wilhelm von Struve 318. The diagram shows the relationship between absolute magnitude (a measure of luminosity) and mass of galaxies called ________. Ans: Galaxy color–magnitude diagram 319. An extended, roughly spherical component of a galaxy which extends beyond the main, visible component called _______. Ans: Galactic halo 320. What is the approximate size of an irregular galaxy compared to the mass of the Milky Way? Ans: One tenth 321. Name the term used for elliptical galaxy that is smaller than ordinary elliptical galaxies. Ans: Dwarf elliptical galaxies

322. About what percentage of all galaxies are considered irregular galaxies? Ans: A quarter 323. Why does the Milky Way appear as a band when observed from Earth? Ans: Because its disk-shaped structure is viewed within. 324. What is the radius of the Solar system from the Galactic Center (in light years)? Ans: About 27,000 light-years 325. The Galactic Cente of milkywayr is an intense radio source known as _________. Ans: Sagittarius A* 326. When did the oldest star in the Milky Way was formed? Ans: Formed shortly after the Dark Ages of the Big Bang. 327. The brighter regions around the band of the Milky way appear as soft visual patches known as _________. Ans: Star clouds 328. ________ are celestial bodies of the universe and continuously emit heat and light. Ans: Stars 329. Compact stars are often the endpoints of stellar evolution, and it is known as ______. Ans: Stellar remnants 330. Name a spiral galaxy tilted face-on to observers on Earth and was the first galaxy whose spiral nature was discerned. Ans: The Whirlpool Galaxy 331. Some regions of the Milky Way's disk appear dark because ________. Ans: Light from stars in that direction are obscured by interstellar dust. 332. Name the most recent directly observed supernova in the Milky Way in 1604 observed with naked eyes. Ans: Kepler's Supernova 333. The Triangulum Galaxy is a source of ______ emission. Ans: H2O maser

334. Blazars are believed to be ______ with a relativistic jet pointed in the direction of Earth. Ans: Active galactic nucleus 335. A galaxy hosting an AGN is called an _______. Ans: Active galaxy 336. When was the first X-ray flare detected from a brown dwarf? Ans: 15 December 1999 337. Most of the galaxies are approximately ________ parsecs in diameter and are separated by distances on the order of millions of parsecs (or megaparsecs). Ans: 1,000 to 100,000 (approximately 3,000 to 300,000 light years) 338. A more compact site of star formation is the opaque clouds of dense gas and dust known as ________. Ans: Bok globules 339.What is the principal source of a young star's energy? Ans: Fusion of hydrogen to helium 340. The spectacular explosion of a super red giant star is called a _______. Ans: Supernova 341. What are the major types of galaxies? Ans: Spiral, elliptical and irregular 342. Name the youngest person who discovered a supernova. Ans: Kathryn Aurora Gray 343. The physical space between galaxies known as _______. Ans: Intergalactic space 344. Name the constellation in which SN 1006, the brightest recorded supernova in 1006 AD appeared. Ans: Lupus 345. In astronomy, _______ is a tightly packed group of stars within a larger formation Ans: Galactic bulge

346. Name the observatory where the first binary pulsar, PSR J0737-3039 discovered. Ans: Parkes Observatory 347. YSO denotes a star in its early stage of evolution. Elaborate YSO. Ans: Young stellar object 348. The comet to be categorized as a lost comet, 34D/Gale is lost since ______. Ans: 1936 349. What is the definition of a life zone around a star? Ans: Area around star with a temperature range in which water can exist in liquid form. 350. Who proposed the existence of the neutron star? Ans: Walter Baade and Fritz Zwicky 351. What is the name of the black hole at centre of the Milky Way? Ans: Sagittarius A* 352. Segue 2 is located near the edge of ______. Ans: Sagittarius Stream 353. A star 20 times the mass of the Sun explodes. What physical type of supernova will occur then? Ans: Type II 354. The method used to record the brightness of a variable star is known as ______. Ans: Photometry 355. Except for black holes and some hypothetical objects (e.g. white holes, quark stars, and strange stars), ______ are the smallest and densest currently known class of stellar objects. Ans: Neutron stars 356. Mira variable stars belong to the group of________ . Ans: Long period variables 357. In astronomy, ______ is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. Ans: Color index

358. Which year the discovery of PSR B1257+12, the first extrasolar planets were announced? Ans: 1994 359. What are the three independent physical properties of a black hole? Ans: Mass, electric charge and angular momentum 360. The Andromeda galaxy owes to the constellation in which it can be found named after Phoenician princess Andromeda, wife of _______ in Greek mythology. Ans: Perseus 361. What is a Progenitor star? Ans: The star that exploded into a supernova is called a progenitor star. 362. Who discovered PSR J1748−2446ad, the fastest spinning neutron star. Ans: Jason W T Hessels 363. Expand 'TOV' in TOV limit. Ans: Tolman Oppenheimer Volkoff 364. Who discovered "an unusual source of high radio brightness temperature in the Crab Nebula". Ans: Antony Hewish and Samuel Okoye 365. _______ is the process by which a star changes over the course of time. Ans: Stellar evolution 366. Name the first black hole which was identified by several researchers independently in 1971. Ans: Cygnus X-1 367. The _______ are a pair of interacting galaxies in the constellation Corvus which was discovered by William Herschel in 1785. Ans: Antennae Galaxies 368. The ______ is a theorized distribution of dark matter which extends throughout the galaxy extending far beyond its visible components. Ans: Dark matter halo

369. The most common method astronomers use to determine the composition of stars, planets, and other objects is ________. Ans: Spectroscopy 370. What was the source of the gravitational waves detected by LIGO in August 2017? Ans: Neutron star merger 371. _______ has a positive correlation with the absolute magnitude (luminosity) of a galaxy. Ans: Metallicity 372. Name the Persian astronomer who was the first to formally describe the Andromeda galaxy in 964 AD. Ans: Abd al-Rahman al-Sufi 373. A jellyfish galaxy is a type of galaxy found in _______. Ans: Galaxy clusters 374. _______ was a series of astrophysical simulations run by an international collaboration of scientists. The aim is to study the processes of galaxy formation and evolution in the universe with a comprehensive physical model. Ans: Illustris project 375. What represents the red color on the Baby Boom galaxy? Ans: Birth of new stars 376. Hoag's Object is an unusual ring galaxy in the constellation of _______. Ans: Serpens Caput 377. In which year the first polar-ring elliptical galaxies were identified? Ans: 1978 378. _______ is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses (M ☉) in a late phase of stellar evolution. Ans: A red giant 379. ______ is a small galaxy which contains large clusters of young, hot, massive stars. These stars, the brightest of which are blue, causethe galaxy itself to appear blue in colour. Ans: Blue Compact Dwarf galaxy (BCD galaxy)

380. Name the smallest and coolest kind of star on the main sequence. Ans: Red dwarf 381. _________ is a binary star in which the orbit plane of the two stars lies so nearly in the line of sight of the observer that the components undergo mutual eclipses. Ans: Eclipsing binary star 382. By observing the pulse rate of pulsar, scientists can determine______. Ans: The neutron star rotation rate 383. Name the plot in which a star is plotted on a graph measuring the star’s brightness against its temperature (color). Ans: Hertzsprung-Russell diagram/ H-R diagram / HRD 384. Globular star clusters are mostly found in________ of a spiral galaxy. Ans: Galaxy halo 385. ________ is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. Ans: A pulsar 386. Approximately how many galaxies were estimated in 2021 from the data of NASA’s New Horizons space probe? Ans: 200 billion galaxies 387. What kind of star will the Sun eventually turn into? Ans: A white dwarf 388. _________ is the physical space within a galaxy beyond the influence of each star on the plasma, the contents of which are called the interstellar medium. Ans: Interstellar space 389. Size and shape of Milky Way galaxy were calculated using ________. Ans: Variable stars 390. When a star runs out of fuel for nuclear fusion and dies in an explosion, it’s called a: ________. Ans: Supernova

391. Abd al-Rahman al-Sufi was the first to formally describe the Andromeda Galaxy referred to in his Book of Fixed Stars as a ________ or ________. Ans: Nebulous smear or small cloud 392. ______ is an astrophysical phenomenon that occurs when the crust of a neutron star undergoes a sudden adjustment, analogous to an earthquake on Earth. Ans: Star quake 393. A spherical group of stars bound together by gravity is called _______. Ans: Globular cluster 394. __________ is thought to be the final evolutionary state of all stars whose mass is not high enough to become a neutron star—over 97% of the stars in the Milky Way. Ans: White dwarf 395. The star that exploded as a supernova is referred to as the _______. Ans: Supernova’s progenitor star 396. Name the type of variable star which is mostly red dwarf star and shows rapid and irregular changes in light. Ans: Flare Star 397. Name the class of hypothetical mega structures which use a star’s radiation to create usable energy. Ans: Stellar engines 398. What is a star tracker? Ans: A star tracker is an optical device that measures the position of a star using a photocell or a camera. 399. ______ is a very young star that is still gathering mass from its parent molecular cloud. Ans: Protostar 400. What is the approximate comoving distance of GN-z11, the oldest and most distant galaxy? Ans: 32 billion light-years from Earth 401. Which are the prominent star constellations in the sky? Ans: Virgo, Hydra, Cetus, Ursa Major, Hercules and Ursa Major.

402. What is the Chandrasekhar limit for a neutron star? Ans: The maximum Chandrasekhar limit for a neutron star is 3 Msun. 403. Where is Teide 1 located? Ans: Teide 1 is located in the Pleiades open star cluster, approximately 400 light-years (120 pc) from Earth. 404. What is the specialty of variable stars? Ans: A variable star is a star whose brightness as seen from Earth (its apparent magnitude) fluctuates. 405. What is a Stellar nursery? Ans: An area of outer space within a dense nebula in which gas and dust are contracting, resulting in the formation of new stars. 406. What is stellar nucleosynthesis? Ans: Stars fuse light elements to heavier ones in their cores, giving off energy in the process known as stellar nucleosynthesis. 407. What is the Tolman Oppenheimer Volkoff limit? Ans: The Tolman Oppenheime Volkoff limit (or TOV limit) is an upper bound to the mass of cold, non-rotating neutron stars, analogous to the Chandrasekhar limit for white dwarf stars. 408. What are stars? Ans: Stars are celestial objects that can generate their own light. They are mostly made up of hydrogen gas with a little helium in them. 409. What are stars made of? Ans: Stars are usually composed of hot gasses. Hydrogen and helium are the main elements in it. 410. How do stars produce light? Ans: Stars create light by nuclear fusion. In this reaction, hydrogen is transformed into helium and energy is generated as a by-product. 411. What happens if a white dwarf exceeds the Chandrasekhar limit? Ans: If a white dwarf exceeds the Chandrasekhar limit, they undergo gravitational collapse and evolve as a stellar remnant similar to a neutron star or a black hole. 412. Why do neutron stars spin so fast?

Ans: Neutron stars can spin many times in a second and that is because of the conservation of angular momentum. 413. What is the event horizon? Ans: In astrophysics, an event horizon is a boundary beyond which events cannot affect an observer. Wolfgang Rindler coined the term in the 1950s. 414. Which types of stars end their life as neutron stars? Ans: The stars whose initial mass is between 8 to 25 times the mass of the Sun, end their life as neutron stars. 415. Which stars become neutron stars? Ans: Any main-sequence star with an initial mass of above 8 times the mass of the sun (8 M ☉) has the potential to produce a neutron star. 416. "Supernova" comes from two Latin words. What are they? Ans: "Super" means "above" or "over," while "nova" means "new." The name is appropriate, since it describes the death of the old and the birth of the new. 417. What beautiful phenomenon often results from a supernova? Ans: The gas and stardust remaining from the explosion form a new nebula. Beautiful color images of nebulae have been captured by the Hubble telescope. 418. What does a supernova sound like? Ans: Sound has no medium through which to travel in space, so you wouldn't hear an explosion if you witnessed a supernova. 419. Is there a limit to the size of a black hole? Ans: The size of the black hole could be up to 50 billion times the mass of our Sun. 420. What does Jeans mass depend on? Ans: The Jeans mass depends on the radius of the cloud, its temperature, and the average mass of the particles in the cloud. 421. What would happen if two neutron stars collided? Ans: The collision would almost instantly form a black hole, given the enormous gravity that each star already produces. The whole process would only take seconds. 422. What causes a Type II supernova?

Ans: A Type II supernova is the natural death of a star. Over time, the star's mass migrates into its core, causing the star to collapse and explode. 423. What can cause a Type I supernova? Ans: Type I supernovae come from binary star systems in which one star takes matter from a neighboring star. Once it grows too large, it explodes. Subcategories of Type I are Ia, Ib and Ic. 424. What useful role do supernovae play in the universe? Ans: Many important elements like helium, hydrogen and carbon are formed during the fusion reactions of stars. When the stars explode, these elements are shot off to the rest of the universe, allowing new stars and planets to form. 425. What is a neutron star made of? Ans: Neutron stars are super dense because they're made up of neutrons (the uncharged particles of atoms) that have been tightly packed together. That means their constituent part is significantly smaller than an atom. 426. What is a Terrestrial Planet? Ans: A terrestrial planet, telluric planet or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Sun i.e Mercury, Venus, Earth and Mars. 427. What is a Giant Gas Cloud? Ans: A star originates from a large cloud of gas. The temperature in the cloud is low enough for the synthesis of molecules. The Orion cloud complex in the Orion system is an example of a star in this stage of life. 428. What causes a neutron star to become a pulsar? Ans: A neutron star becomes a pulsar under specific conditions, with the right mix of magnetic field and spin frequency. Slow pulsars rotate about once per second, while some rotate up to 700 times per second. 429. What is a radio-quiet neutron star? Ans: A radio-quiet neutron star is a neutron star that does not seem to emit radio emissions, but is still visible to Earth through electromagnetic radiation at other parts of the spectrum, particularly X-rays and gamma rays. 430. What is Retrograde motion?

Ans: Retrograde motion means the orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object. It may also describe other motions such as precession or nutation of an object's rotational axis. 431. What are Type B Stars? Ans: Type B stars are main-sequence stars that are similar to, but somewhat cooler and less massive than type O stars. Generally, they are between 2 and 16 times the mass of the sun with surface temperatures between 10,000K and 30,000K. 432. What elements are released when a star dies? Ans: When the core runs out of hydrogen, these stars fuse helium into carbon just like the Sun. However, after the helium is gone, their mass is enough to fuse carbon into heavier elements such as oxygen, neon, silicon, magnesium, sulfur and iron. 433. Who first discovered white dwarf? Ans: In 1917, Adriaan van Maanen discovered Van Maanen's Star, an isolated white dwarf. These three white dwarfs, the first discovered, are the so-called classical white dwarfs. 434. What is Chandrasekhar Unit? Ans: Chandrasekhar unit is used for explaining the maximum mass of a white dwarf star which is equivalent to 1.44 solar masses. When the limit exceeds the star into a neutron star or a black hole. 435. Define star formation. Ans: Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. 436. What happened in the nucleosynthesis era? Ans: At the end of the Era of Nucleosynthesis, the universe contained the "primordial" mix of hydrogen, helium and lithium that went into making the first stars. All heavier elements have been created by fusion inside of stars and during supernova explosions. 437. What is the significance of the Chandrasekhar limit? Ans: The significance of the Chandrasekhar limit is that it is accepted to be 1.4 times the mass of the Sun such that if the white dwarf is within the limit they stay as such forever whereas the star that exceeds the limit will experience explosions turning into a supernova. 438. What is the first step in nucleosynthesis?

Ans: Stellar nucleosynthesis is the process involving nuclear reactions through which fresh atomic nuclei are synthesized from pre-existing nuclei or nucleons. The first stage of nucleosynthesis occurred in the hot, early Universe, with the production of H, He and traces of Li-7. 439. What are the different types of stars? Ans: Stars can be categorized as per their temperature and mass. Based on decreasing temperature, stars are categorized into O, B, A, F, G, K and M. M stars are common, dim, cooler and yellow or red in color. On the other hand, O stars are rare, very bright, hot and blue or white in color. 440. What are Type G Stars? Ans: The most famous G type star is our own Sun (type G2V), a full description of which is available in the Solar System section. This type of star typically weighs about 0.8 to 1.25 times the mass of the Sun. Surface temperatures are typically between 5,300K and 6,000K. 441. What are Type K Stars? Ans: K type stars are generally somewhat lighter than the Sun, though they may be considerably larger and much heavier. They tend to be very stable and long lived, and as there are between three and four times as many type K stars as there are type G, they are very interesting to those searching for extraterrestrial life. 442. What is Jeans mass equation? Ans: The Jeans mass is the mass that a spherical cloud of interstellar gas must have in order to contract under its own weight. Jeans mass is proportional to the ratio of the temperature to the mean mass per particle to the 3/2 power divided by the square root of the mass density. 443. What is Jean radius? Ans: Jeans' length is the critical radius of a cloud where thermal energy, which causes the cloud to expand, is counteracted by gravity, which causes the cloud to collapse. It is named after the British astronomer Sir James Jeans, who concerned himself with the stability of spherical nebulae in the early 1900s. 444. Write a few words on Eris. Ans: Eris is the largest dwarf planet in the solar system and is the largest object found in orbit around the Sun since the discovery of Neptune and its moon Triton in 1846. It has a diameter between 2,400 and 3,000 kilometres (1,490 to 1,860 miles) and is 27% more massive than Pluto. 445. Why are the two bright stars in the cup of the Big Dipper called the pointers?

Ans: Finding the Big Dipper in the night sky is the easiest way to find Polaris, the North Star, located in the constellation Ursa Minor, the Little Bear. Merak and Dubhe are the stars that mark the end of the bowl of the Big Dipper. They are called the Pointer Stars because they point the way to Polaris and true north. 446. What is a harvest moon and when does it occur? Ans: Harvest moon, the full moon nearest the autumnal equinox (about September 23). Near the time of the autumnal equinox, the angle of the moon's orbit relative to the Earth's horizon is at its minimum, causing the full moon to rise above the horizon much faster than usual. 447. What is Prograde motion? Ans: Prograde or direct motion is a more normal motion in the same direction as the primary rotates. However, "retrograde" and "prograde" can also refer to an object other than the primary if so described. The direction of rotation is determined by an inertial frame of reference, such as distant fixed stars. 448. What is a small Solar System body? Ans: A small Solar System body (SSSB) is an object in the Solar System that is neither a planet, a dwarf planet nor a natural satellite.The term was first defined in 2006 by the International Astronomical Union as follows: All other objects, except satellites, orbiting the Sun shall be referred to collectively as Small Solar System Bodies. 449. Do planets ever appear to rise in the west? Ans: Although planets can sometimes be mistaken for stars as one observes the night sky, the planets actually change position from night to night in relation to the stars. Like the sun, the planets appear to rise in the East and set in the West. When a planet travels eastward in relation to the stars, it is called prograde. 450. What are brown dwarfs made of? Ans: Brown dwarfs are failed stars about the size of Jupiter, with a much larger mass but not quite large enough to become stars. Like the Sun and Jupiter, they are composed mainly of hydrogen gas, perhaps with swirling cloud belts. Unlike the Sun, they have no internal energy source and emit almost no visible light. 451. Who detected Teide 1? Ans: Teide 1 is detected by Rafael Rebolo López, María R. Zapatero-Osorio and Eduardo L. Martín on optical images obtained, in January 1994, with the 0.80 meter diameter telescope (IAC-80) from the Instituto de Astrofísica de Canarias located at the Teide Observatory on the island of Tenerife.

452. What is a carbon star? Ans: A carbon star is a late-type star similar to a red giant (or occasionally to a red dwarf) whose atmosphere contains more carbon than oxygen; the two elements combine in the upper layers of the star, forming carbon monoxide, which consumes all the oxygen in the atmosphere, leaving carbon atoms free to form other carbon compounds, giving the star a “sooty” atmosphere and a strikingly ruby red appearance. 453. What is MWC 349? Ans: MWC 349 is a double (likely, triple) star system in the constellation Cygnus. Its properties are still debated and it may be a massive highly luminous star or a very young less luminous Herbig Ae/Be star. MWC 349 is also a variable star with the designation V1478 Cygni. 454. What is a T-Tauri Phase? Ans: A T-Tauri star begins when materials stop falling into the Protostar and release tremendous amounts of energy. The mean temperature of the Tauri star isn’t enough to support nuclear fusion at its core. The T-Tauri star lasts for about 100 million years, following which it enters the most extended phase of development – the Main sequence phase. 455. What is a Main Sequence? Ans: The main sequence phase is the stage in development where the core temperature reaches the point for the fusion to commence. In this process, the protons of hydrogen are converted into atoms of helium. This reaction is exothermic; it gives off more heat than it requires and so the core of a main-sequence star releases a tremendous amount of energy. 456. What is a brown dwarf? Ans: Brown dwarfs are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen into helium in their cores, unlike a main-sequence star. They have a mass between the most massive gas giant planets and the least massive stars, approximately 13 to 80 times that of Jupiter. 457. Is a protostar a star? Ans: A protostar looks like a star but its core is not yet hot enough for fusion to take place. The luminosity comes exclusively from the heating of the protostar as it contracts. Protostars are usually surrounded by dust, which blocks the light that they emit, so they are difficult to observe in the visible spectrum. 458. What is a blackhole?

Ans: A black hole is a region of spacetime where gravity is so strong that nothing, no particles or even electromagnetic radiation such as light can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. 459. What is a Globular cluster? Ans: A globular cluster is a spherical collection of stars. Globular clusters are very tightly bound by gravity, with a high concentration of stars towards their centers. Their name is derived from Latin globulus-a small sphere. Globular clusters are occasionally known simply as globulars. 460. What is Sub-brown dwarf? Ans: Objects below 13 MJ, called sub-brown dwarf or planetary-mass brown dwarf, form in the same manner as stars and brown dwarfs (i.e. through the collapse of a gas cloud) but have a mass below the limiting mass for thermonuclear fusion of deuterium. Some researchers call them free-floating planets, whereas others call them planetary-mass brown dwarfs. 461. Explain the Fusion of Heavier Elements. Ans: Helium molecules fuse at the core, as the star expands. The energy of this reaction prevents the core from collapsing. The core shrinks and begins fusing carbon, once the helium fusion ends. This process repeats until iron appears at the core. The iron fusion reaction absorbs energy, which causes the core to collapse. This implosion transforms massive stars into a supernova while smaller stars like the sun contract into white dwarfs. 462. Explain the processes behind the star formation. Ans: The formation of stars occurs exclusively within molecular clouds. This is a natural consequence of their low temperatures and high densities, because the gravitational force acting to collapse the cloud must exceed the internal pressures that are acting "outward" to prevent a collapse. There is observed evidence that the large, star-forming clouds are confined to a large degree by their own gravity (like stars, planets, and galaxies) rather than by external pressure. The evidence comes from the fact that the "turbulent" velocities inferred from CO linewidth scale in the same manner as the orbital velocity (a virial relation). 463. List down the process of the formation of stars like the Sun. Ans: 

An interstellar cloud

A collapsing cloud fragment

Fragmentation ceases

A protostar

Protostellar evolution

A newborn star

The main sequence star

464. Write a short note on Interstellar cloud. Ans: An interstellar cloud is generally an accumulation of gas, plasma, and dust in our and other galaxies. Put differently, an interstellar cloud is a denser than average region of the interstellar medium (ISM), the matter and radiation that exists in the space between the star systems in a galaxy. Depending on the density, size and temperature of a given cloud, its hydrogen can be neutral, making an H I region; ionized or plasma making it an H II region; or molecular, which are referred to simply as molecular clouds, or sometimes dense clouds. Neutral and ionized clouds are sometimes also called diffuse clouds. An interstellar cloud is formed by the gas and dust particles from a red giant in its later life. 465. What are stellar remnants? Ans: The term compact star (or compact object) refers collectively to white dwarfs, neutron stars, and black holes. It would grow to include exotic stars if such hypothetical, dense bodies are confirmed to exist. All compact objects have a high mass relative to their radius, giving them a very high density, compared to ordinary atomic matter. Compact stars are often the endpoints of stellar evolution, and are in this respect also called stellar remnants. The state and type of a stellar remnant depends primarily on the mass of the star that it formed from. 466. What is Protostar? Ans: A Protostar is a very young star that is still gathering mass from its parent molecular cloud. The protostellar phase is the earliest one in the process of stellar evolution. For a low-mass star, it lasts about 500,000 years. The phase begins when a molecular cloud fragment first collapses under the force of self-gravity and an opaque, pressure supported core forms inside the collapsing fragment. It ends when the infalling gas is depleted, leaving a pre-mainsequence star, which contracts to later become a main-sequence star at the onset of hydrogen fusion producing helium. 467. Why is Pluto considered as a dwarf planet? Ans: Pluto is considered a dwarf planet. This is called so because it has not cleared its neighborhood around its orbit. The International Astronomical Unit declared it a Dwarf Planet in 2006. It orbits in a disc-like zone beyond the orbit of Neptune called the Kuiper belt, a distant region populated with frozen bodies left over from the solar system’s formation. 468. What are the applications of the Chandrasekhar Limit? Ans: The applications of Chandrashekar limit are as follows:

When the nuclei of lighter elements fuse into the nuclei of a heavier one the resultant heat is what keeps the core of the star from collapsing. The core will become condensed and hotter when collapsed as the exhaustion of the nuclei will take place.

As getting energy through fusion is impossible in the case of iron ions, a dangerous circumstance occurs when iron amasses in the core. If the star is less than 8 solar masses, it will sooner or later get to a mass level lower than the Chandrasekhar limit.

Stars that have more mass will be converted into a black hole as the pressure due to the electron degeneration will keep them from collapsing until the density is extremely high. Neutrinos are released when through electrons capturing the electrons are captured by the protons. The released neutrinos take away the energy that was created due to the decreasing potential energy (collapse of the core). The energy is around 1046 joules.

469. What would happen if a neutron star hit a black hole? Ans: When a massive celestial body such as a neutron star hits a black hole, there is a production of gravitational waves that ripple through the fabric of space-time. Also, there will be the release of nuclear materials such as gold and platinum along with electromagnetic waves. These electromagnetic waves include light waves and gravitational waves. 470. What Red Giant? Ans: A star converts hydrogen atoms into helium over its course of life at its core. Eventually, the hydrogen fuel runs out, and the internal reaction stops. Without the reactions occurring at the core, a star contracts inward through gravity causing it to expand. As it expands, the star first becomes a subgiant star and then a red giant. Red giants have cooler surfaces than the main-sequence star, and because of this, they appear red than yellow. 471. Write a short note on the life cycle of a star. Ans: All stars form in nebulae, which are huge clouds of gas and dust. Though they shine for many thousands and even millions of years, stars do not last forever. The changes that occur in a star over time and the final stage of its life depend on a star's size. Nuclear reactions at the center (or core) of a star provides energy which makes it shine brightly. This stage is called the 'main sequence'. The exact lifetime of a star depends very much on its size. Very massive stars use up their fuel quickly. This means they may only last a few hundred thousand years. Smaller stars use up fuel more slowly so will shine for several billion years. Eventually, the hydrogen which powers the nuclear reactions inside a star begins to run out. The star then enters the final phases of its lifetime. All stars will expand, cool and change color to become a red giant. What happens next depends on how massive the star is.

A smaller star, like the Sun, will gradually cool down and stop glowing. During these changes it will go through the planetary nebula phase and white dwarf phase. After many thousands of millions of years it will stop glowing and become a black dwarf. A massive star experiences a much more energetic and violent end. It explodes as a supernova. This scatters materials from inside the star across space. This material can collect in nebulae and form the next generation of stars. After the dust clears, a very dense neutron star is left behind. These spin rapidly and can give off streams of radiation, known as pulsars. If the star is especially massive, when it explodes it forms a black hole. 472. What is stellar evolution? Explain the evolution of a star from its birth up to the red giant stage. Ans: The process from the birth to the death of a star is called stellar evolution. 

Inter steller space contains huge gaseous clouds. These gaseous clouds contracts due to their own gravity.

The central portion alone accounts for 99% of the mass of the cloud. The sphere formed at the centre is called Protostar.

The centre of the protostar pressure and temperature reaches about

10 million kelvin, some of the hydrogen nucleusfuses to for helium nucleus producing a large amount of energy.

Due to the producing of enormous amount of energy there will be force acting outwards, which tends to expand the star. Thus, the star reaches a steady state.

When the star reaching steady state, it will start giving out steady output energy. As the radiation pressure increases beyond the opposing gravitational pull, the star begins to swell consequently, the surface area will be more. As a result of this, the temperature of the star decreases hence emits light which is low frequency radiation then the star is said to be a red giant.

473. Supernovae leave behind neutron stars or black holes. Explain Ans: Main sequence stars over eight solar masses are destined to die in a titanic explosion called a supernova. A supernova is not merely a bigger nova. In a nova, only the star's surface explodes. In a supernova, the star's core collapses and then explodes. In massive stars, a complex series of nuclear reactions leads to the production of iron in the core. Having achieved iron, the star has wrung all the energy it can out of nuclear fusion - fusion reactions that form elements heavier than iron actually consume energy rather than produce it. The star no longer has any way to support its own mass, and the iron core collapses. In just a matter of seconds the core shrinks from roughly 5000 miles across to just a dozen, and the temperature spikes 100 billion degrees or more. The outer layers of the star initially begin to collapse along with the core, but rebound with the enormous release of energy and are thrown violently outward. Supernovae release an almost unimaginable amount of energy.

For a period of days to weeks, a supernova may outshine an entire galaxy. Likewise, all the naturally occurring elements and a rich array of subatomic particles are produced in these explosions. On average, a supernova explosion occurs about once every hundred years in the typical galaxy. About 25 to 50 supernovae are discovered each year in other galaxies, but most are too far away to be seen without a telescope. 474. When does a star become a super red giant? Ans: A star can become a super red giant in the last parts of its life, if its mass is greater than 8 times the Sun's mass. After the supernova, the super red giant would become a neutron star, if its mass lies between 8 and 25 times the mass of the Sun, and would become a black hole, if it is greater than 25 times the mass of the Sun. 475. Which are the last two stages of a star? Ans: The last two stages of star are as follows:  

White Dwarf Black dwarf White dwarf: The star collapses under the action of gravity. The temperature increases and the core develops pressure. It shines due to their high temperature. Black dwarf: In this stage the star loses its energy (internal) and temperature, stopping the nuclear reactions which were taking place.

476. How do stars form? Ans: Spaces between the stars present in a galaxy are occupied by huge clouds of gas and dust, known as interstellar clouds. Contractions happen in this cloud due to some natural disturbance. Because of this, the density and temperature in the cloud starts increasing and a dense sphere of hot gas is formed from the cloud. Nuclear energy (energy released due to fusion of atomic nuclei) is generated with the burning of fuel, like hydrogen and helium, in the sphere when it attains a sufficient amount of density and temperature at its center. Due to this energy generation, the gas sphere becomes self-luminous and thus a new star is formed. 477. Why do stars evolve? Ans: Star loses its energy constantly due to continuous emission of light and energy. This means that the temperature of a star decreases continuously and hence its gas pressure which thereby decreases its stability. But we know a star is very stable. So, to maintain the stability of a star, its temperature is maintained constant with the help of energy released by the burning of fuel at its center. This burning and therefore the decrease in the amount of fuel is the reason for the evolution in the stars.

478. What is a Carbon star? Ans: A carbon star (C-type star) is typically an asymptotic giant branch star, a luminous red giant, whose atmosphere contains more carbon than oxygen. The two elements combine in the upper layers of the star, forming carbon monoxide, which consumes all the oxygen in the atmosphere, leaving carbon atoms free to form other carbon compounds, giving the star a "sooty" atmosphere and a strikingly ruby red appearance. There are also some dwarf and supergiant carbon stars, with the more common giant stars sometimes being called classical carbon stars to distinguish them. 479. What are Type O Stars? Ans: Class O stars are very hot and very luminous, some stars being over one million times more luminous than the Sun. Most of their output is in the ultraviolet range giving the stars a blue color. They are some of the rarest and most massive of all stars. Being so massive, and consequently very hot, they burn through their hydrogen very quickly, in some cases within a few million years. Almost all are fated to end their brief lives in spectacular supernova explosions. eg: Zeta Orionis Aa, Zeta Puppis (Naos) 480. What are Type A Stars? Ans: Class A stars are blue-white to white, and are relatively common in the local neighborhood. Generally, they weigh between 1.4 and 2.1 times the mass of the Sun, but Deneb, for example, shows how much they can vary from the norm. Surface temperatures vary between approximately 7,600K and 10,000K. eg: Sirius, Vega 481. What are Type F Stars? Ans: Class F main-sequence stars are yellow-white dwarfs, usually weighing between 1.0 and 1.4 times the mass of the Sun but, again, there is great variability. Stars are yellow/white with surface temperatures between about 6,000K and 7,600K. The best-known example, at least in the Northern Hemisphere, is the Pole Star (Polaris). Canopus, possibly a rare Class F giant, is the brightest Southern Hemisphere star. 482. What are Type M Stars? Ans: Type M stars are the most common type of stars. Astronomers define them by their optical spectrum which tends to be dominated by absorption bands of titanium oxide and vanadium oxide. While most of the stars in this class are main sequence and red dwarf types, it also includes a number of giant stars, as well as some super-giants & hyper-giants; including VY Canis Majoris the largest known star, though UY Scuti may be larger depending upon its distance from us. 483. Explain about Variable Stars.

Ans: Variable Stars refers to stars that change their apparent luminosity, as seen from Earth. To some extent, all stars exhibit variability; even the Sun changes its luminosity by about 0.1% over the 11 years sunspot cycle. To be classified as a variable star, however, requires a more profound change. There are two main categories of variables; Intrinsic and Extrinsic. Additional classification is complex and based on the physical processes that cause the variability. Some sub-classes of variable stars are named after a prototype; for example, the RR Lyrae type. 484. Write a short note on Class L Dwarf Stars. Ans: Cooler than Type M stars they have temperatures in the range 1,300K to 2,000K, and are typically a red-brown color. The classic example is GD 165B, which lacks the vanadium and titanium oxides of warmer type M dwarfs, but shows hydroxides. Although designated dwarfs, some can be rather large; for example, the rather mysterious star V838 Monocerotis could be the first type L supergiant. In a February 2002 eruption, it expanded to become more than 1,500 times the size of the Sun; it would reach the orbit of Jupiter. Prior to the eruption, it was probably five to ten times the mass of the Sun, and up to five times the diameter. The reason for the eruption remains conjectural, and includes possibilities as diverse as an atypical nova, a merge with a much smaller star (a so-called Luminous Red Nova), or possibly engulfing large gas giant planets that had been in orbit. These stars are identified by metal hydride emission bands (FeH, CrH, MgH, CaH) and prominent alkali metal lines (Na I, K I, Cs I, Rb I). GD 165B is the prototype star of the "L" type dwarfs. 485. Write a short note on Class T Methane Dwarfs. Ans: Even cooler with surface temperatures in the range 700º to 1,300º K, they would appear as a dark magenta color. Not surprisingly, they have an abundance of Methane in their spectra. It is thought that there may be a huge number of these, and type L dwarfs, that we are unable to see. Their lifetimes tend to be incredibly long, for the light weight dwarfs, so numbers would continue to increase. The first identified was Gliese 229B, which orbits the red dwarf Gliese 229A. Its surface temperature is estimated to be below 1,000º K and it weighs only about 2% to 5% the mass of the Sun, or about 20 to 50 times the mass of Jupiter. Remember, a candle flame is between 1,350 and 1,650º K or so! Gliese 229B is the smaller object in the image to the right orbiting its larger companion Gliese 229A. They are about 19 light years away. Gliese 229B is the prototype of the "T" type dwarfs. Their spectra are dominated by absorption bands from methane and have very broad absorption features from the alkali metals Na and K. They also lack the FeH and CrH bands that "L" type dwarfs exhibit. Another example is the binary pair Epsilon Indi Ba (T1V) & Bb (T6V) which are in orbit around Epsilon Indi itself. Epsilon Indi Ba, the larger of the pair, weighs about 4.5% of the Sun, while it is about 9% the diameter, with a temperature of 1,280K. Epsilon Indi Bb,

meanwhile, weighs about 2.7% of the Sun, while it is about 9.6% the diameter, with a surface temperature of only 850K. Both are similar in size to Jupiter, but much heavier and, therefore, denser. 486. Write a short note on Class Y Ultra-Cool Brown Dwarfs. Ans: This is a theoretical classification suggested for brown dwarfs that are even cooler than T dwarfs, at less than 600º K and without the methane content. Until early 2011, no confirmed example had been identified. A very dim brown dwarf, with the catchy name UGPS J072227.51-054031.2, was a candidate, though it is currently defined as a type T10. It is about 13 light-years away, so in our stellar back yard, and was discovered in 2010. It is barely warm with a surface temperature around 480K to 560K (207º to 287º C or 405º to 549º F). About the same size as Jupiter, it weighs about 5 to 30 times as much, which is between about 0.5% and 3% the mass of the Sun; so cool and small. In March 2011, NASA announced that the smaller, and cooler, of a pair of brown dwarfs named CFBDSIR 1458+10 has a surface temperature of about 370K, the boiling point of water and could well be a type Y. In fact, it is possible that it could have water clouds in its atmosphere. It is about 75 light-years away, and weighs about 5 to 15 times as much as Jupiter. The pair were imaged by the Keck telescope in Hawaii. Shortly after the Keck announcement, NASA released information from the Spitzer telescope about an extremely cool brown dwarf star found about 63 light-years from Earth. It has only about seven times the mass of Jupiter, but the real surprise is that it appears to have a surface temperature of about 300K (30º C or 86º F); equivalent to a warm summer day. The star, WD 0806-661B orbits a white dwarf star known as WD 0806-661at a distance of 2,500 AU (nearly 375 billion km, or more than 230 billion miles). It is a strong candidate for being a Class Y star as are WISE 1828+2650 and WISE 0855-0714. 487. Write a short note on Neptune’s weather. Ans: Neptune's weather is characterised by extremely dynamic storm systems, with winds reaching speeds of almost 600 m/s (2,200 km/h; 1,300 mph)—nearly reaching supersonic flow. More typically, by tracking the motion of persistent clouds, wind speeds have been shown to vary from 20 m/s in the easterly direction to 325 m/s westward. At the cloud tops, the prevailing winds range in speed from 400 m/s along the equator to 250 m/s at the poles. Most of the winds on Neptune move in a direction opposite the planet's rotation. The general pattern of winds showed prograde rotation at high latitudes vs. retrograde rotation at lower latitudes. The difference in flow direction is thought to be a "skin effect" and not due to any deeper atmospheric processes. At 70° S latitude, a high-speed jet travels at a speed of 300 m/s. 488. Why is only one side of the Moon visible from Earth?

Ans: Only one side of the Moon is visible from Earth because the Moon rotates on its axis at the same rate that the Moon orbits the Earth, a situation known as synchronous rotation or tidal locking. The Moon is directly illuminated by the Sun and the cyclically varying viewing conditions cause the lunar phases. Sometimes the dark portion of the Moon is faintly visible due to earthshine which is indirect sunlight reflected from the surface of Earth and onto the Moon. Since the Moon's orbit is both somewhat elliptical and inclined to its equatorial plane, libration allows up to 59% of the Moon's surface to be viewed from Earth (though only half at any moment from any point). 489. How did Galileo prove the Earth was not the center of the solar system? Ans: Nicholas Copernicus, a Polish scientist living about a century before Galileo, had already come up with the unorthodox idea that the Sun was at the center of the solar system. Galileo knew about and had accepted Copernicus's heliocentric (Sun-centered) theory. It was Galileo's observations of Venus that proved the theory. Using his telescope, Galileo found that Venus went through phases, just like our Moon. But, the nature of these phases could only be explained by Venus going around the Sun, not the Earth. Galileo concluded that Venus must travel around the Sun, passing at times behind and beyond it, rather than revolving directly around the Earth. Galileo's observations of the phases of Venus virtually proved that the Earth was not the center of the universe. 490. Explain quasi conjunction. Ans: In a quasi-conjunction, a planet in retrograde motion always either Mercury or Venus from the point of view of the Earth, will "drop back" in right ascension until it almost allows another planet to overtake it but then the former planet will resume its forward motion and thereafter appear to draw away from it again. This will occur in the morning sky, before dawn. The reverse may happen in the evening sky after dusk with Mercury or Venus entering retrograde motion just as it is about to overtake another planet. The quasi conjunction is reckoned as occurring at the time the distance in right ascension between the two planets is smallest even though when declination is taken into account, they may appear closer together shortly before or after this.

491. Write a note on planet Mercury. Ans: The smallest planet in our solar system and nearest to the Sun, Mercury is only slightly larger than Earth's Moon. From the surface of Mercury, the Sun would appear more than three times as large as it does when view from Earth and the sunlight would be as much as seven times brighter. Mercury's surface temperatures are both extremely hot and cold. Because the planet is so close to the Sun, day temperatures can reach highs of 800°F (430°C). Without an atmosphere to retain that heat at night, temperatures can dip as low as -290°F (-180°C).

Mercury's highly eccentric, egg-shaped orbit takes the planet as close as 29 million miles (47 million kilometers) and as far as 43 million miles (70 million kilometers) from the Sun. It speeds around the Sun every 88 days, traveling through space at nearly 29 miles (47 kilometers) per second, faster than any other planet. Mercury spins slowly on its axis and completes one rotation every 59 Earth days. But when Mercury is moving fastest in its elliptical orbit around the Sun (and it is closest to the Sun), each rotation is not accompanied by sunrise and sunset like it is on most other planets. The morning Sun appears to rise briefly, set and rise again from some parts of the planet's surface. The same thing happens in reverse at sunset for other parts of the surface. One Mercury solar day (one full day-night cycle) equals 176 Earth days – just over two years on Mercury. 492. Explain the planet Venus. Ans: Venus is the second planet from the Sun.It is named after the Roman goddess of love and beauty. As the brightest natural object in Earth's night sky after the Moon. Venus orbits the Sun every 224.7 Earth days. It has a synodic day length of 117 Earth days and a sidereal rotation period of 243 Earth days. As a consequence, it takes longer to rotate about its axis than any other planet in the solar system, and does so in the opposite direction to all but Uranus. This means the Sun rises in the west and sets in the east. Venus does not have any moons. Venus is a terrestrial planet and is sometimes called Earth's "sister planet" because of their similar size, mass, proximity to the Sun, and bulk composition. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is about 92 times the sea level pressure of Earth, or roughly the pressure at 900 m (3,000 ft) underwater on Earth. Even though Mercury is closer to the Sun, Venus has the hottest surface of any planet in the Solar System, with a mean temperature of 737 K (464 °C; 867 °F). It was the first planet beyond Earth visited by a spacecraft (Venera 1 in 1961), and the first to be successfully landed on (by Venera 7 in 1970). Venusian thick clouds render observation of its surface impossible in the visible spectrum, and the first detailed maps did not emerge until the arrival of the Magellan orbiter in 1991. 493. Write a note on Mars. Ans: Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System. It is also known as the "Red Planet". The latter refers to the effect of the iron oxide prevalent on Mars's surface, which gives it a reddish appearance that is distinctive among the astronomical bodies visible to the naked eye. Mars is a terrestrial planet with a thin atmosphere, with surface features reminiscent of the impact craters of the Moon, and the valleys, deserts and polar ice caps of Earth. The days and seasons are comparable to those of Earth, because the rotation period as well as the tilt of the rotational axis relative to the ecliptic plane are similar. Mars is approximately half the diameter of Earth, with a surface

area only slightly less than the total area of Earth's dry land. Mars is the site of Olympus Mons, the largest volcano and highest known mountain on any planet in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the Northern Hemisphere covers 40% of the planet and may be a giant impact feature. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. Mars has been explored by several uncrewed spacecraft. Mariner 4 was the first spacecraft to visit Mars; launched by NASA on 28 November 1964, it made its closest approach to the planet on 15 July 1965. 494. Explain about nebular hypothesis. Ans: The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting the Sun. The theory was developed by Immanuel Kant and published in his Universal Natural History and Theory of the Heavens (1755) and then modified in 1796 by Pierre Laplace. The widely accepted modern variant of the nebular theory is the solar nebular disk model (SNDM) or solar nebular model. It offered explanations for a variety of properties of the Solar System, including the nearly circular and coplanar orbits of the planets, and their motion in the same direction as the Sun's rotation. Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded. 495. Write a short note on the interstellar medium (ISM). Ans: The interstellar medium (ISM) is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space. The energy that occupies the same volume, in the form of electromagnetic radiation, is the interstellar radiation field. The interstellar medium is composed of multiple phases distinguished by whether matter is ionic, atomic, or molecular, and the temperature and density of the matter. The interstellar medium is composed, primarily, of hydrogen, followed by helium with trace amounts of carbon, oxygen, and nitrogen comparatively to hydrogen. The thermal pressures of these phases are in rough equilibrium with one another. Magnetic fields and turbulent motions also provide pressure in the ISM and are typically more important, dynamically, than the thermal pressure. 496. What is Supernova remnant (SNR)? Ans: A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of

ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way. A supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light (or approximately 30,000 km/s). These speeds are highly supersonic, so a strong shock wave forms ahead of the ejecta. That heats the upstream plasma up to temperatures well above millions of K. The shock continuously slows down over time as it sweeps up the ambient medium, but it can expand over hundreds or thousands of years and over tens of parsecs before its speed falls below the local sound speed. One of the best observed young supernova remnants was formed by SN 1987A, a supernova in the Large Magellanic Cloud that was observed in February 1987. Other well-known supernova remnants include the Crab Nebula; Tycho, the remnant of SN 1572, named after Tycho Brahe who recorded the brightness of its original explosion; and Kepler, the remnant of SN 1604, named after Johannes Kepler. The youngest known remnant in our galaxy is G1.9+0.3, discovered in the galactic center. 497. Explain about the naming of the supernova. Ans: Supernova discoveries are reported to the International Astronomical Union's Central Bureau for Astronomical Telegrams, which sends out a circular with the name it assigns to that supernova. The name is formed from the prefix SN, followed by the year of discovery, suffixed with a one or two-letter designation. The first 26 supernovae of the year are designated with a capital letter from A to Z. Afterward pairs of lower-case letters are used: aa, ab, and so on. Hence, for example, SN 2003C designates the third supernova reported in the year 2003. The last supernova of 2005, SN 2005nc, was the 367th (14 × 26 + 3 = 367). Since 2000, professional and amateur astronomers have been finding several hundred supernovae each year (572 in 2007, 261 in 2008, 390 in 2009; 231 in 2013). Historical supernovae are known simply by the year they occurred: SN 185, SN 1006, SN 1054, SN 1572 (called Tycho's Nova) and SN 1604 (Kepler's Star). Since 1885 the additional letter notation has been used, even if there was only one supernova discovered that year (e.g. SN 1885A, SN 1907A, etc.)—this last happened with SN 1947A. SN, for SuperNova, is a standard prefix. Until 1987, two-letter designations were rarely needed; since 1988, however, they have been needed every year. Since 2016, the increasing number of discoveries has regularly led to the additional use of three-digit designations. 498. Write a short note on Kepler's Supernova. Ans: SN 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a Type Ia supernova that occurred in the Milky Way, in the constellation Ophiuchus. Appearing in 1604, it is the most recent supernova in our galaxy to have been unquestionably observed by the naked eye,occurring no farther than 6 kiloparsecs (20,000 light-years) from Earth. Before the adoption of the current naming system for supernovae, it was named for Johannes

Kepler, the German astronomer who described it in De Stella Nova. A dim nebula was discovered in 1941 at the Mount Wilson Observatory with a brightness of 19 mag which is the supernova remnant of SN 1604. Only filaments can be seen in visible light. It is however a strong radio source. Its diameter is 4 arcmin. Its distance is not well determined but is between 3 and more than 7 kiloparsec (10,000 to 23,000 lightyears). 499. Explain about type 1a supernova. Ans: A type 1a supernova is a type of supernova that occurs in binary systems in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white dwarf. Type I supernovae are subdivided on the basis of their spectra, with type Ia showing a strong ionized silicon absorption line. Type I supernovae without this strong line are classified as type Ib and Ic, with type Ib showing strong neutral helium lines and type Ic lacking them. The light curves are all similar, although type Ia are generally brighter at peak luminosity, but the light curve is not important for classification of type I supernovae. A small number of type Ia supernovae exhibit unusual features, such as non-standard luminosity or broadened light curves, and these are typically classified by referring to the earliest example showing similar features. For example, the sub-luminous SN 2008ha is often referred to as SN 2002cx-like or class Ia-2002cx. 500. Explain about the type II supernovae. Ans: The supernovae of type II can also be subdivided based on their spectra. While most type II supernovae show very broad emission lines which indicate expansion velocities of many thousands of kilometers per second, some, such as SN 2005gl, have relatively narrow features in their spectra. These are called type IIn, where the 'n' stands for 'narrow'. A few supernovae, such as SN 1993J, appear to change types: they show lines of hydrogen at early times, but, over a period of weeks to months, become dominated by lines of helium. The term "type IIb" is used to describe the combination of features normally associated with types II and Ib. Type II supernovae with normal spectra dominated by broad hydrogen lines that remain for the life of the decline are classified on the basis of their light curves. The most common type shows a distinctive "plateau" in the light curve shortly after peak brightness where the visual luminosity stays relatively constant for several months before the decline resumes. These are called type II-P referring to the plateau. Less common are type II-L supernovae that lack a distinct plateau. The "L" signifies "linear" although the light curve is not actually a straight line. Supernovae that do not fit into the normal classifications are designated peculiar, or 'pec'.