135 FAQs about Galaxies (The Astronomy Cafe)

The Milky Way: Basic Information

The Milky Way at many wavelengths: Radio to gamma ray images

Hubble Space Telescope pictures Assorted Galaxies

Beautiful ground-based sky images: Colorful and Spectacular

Infrared image from inside the Milky Way looking out: NASA COBE satellite

  1. Are there any more big galaxies hidden behind the Milky Way in our Local Group?
  2. Does the Milky Way move in space or does it just stay put?
  3. Where can I find a 3-D map of the Milky Way?
  4. What kind of a galaxy is Malin 1 ?
  5. Where do the jets in active galactic nuclei come from?
  6. How can amino acids such as Glycine exist under the harsh conditions of interstellar space?
  7. Where can I get a copy of the Hubble Deep Field photograph?
  8. Do all stars belong to galaxies?
  9. Are the properties inside 'Local Bubbles' the same everywhere?
  10. If all galaxies have black holes in their cores, why do some of them emit streams of particles in 'jets'?
  11. What is the 'very rapid burster' in the center of our galaxy?
  12. What is the 'Ring Galaxy' mentioned by Carl Sagan in an interview?
  13. How many spiral arms does the Milky Way have?
  14. How do we know the Milky Way is a spiral galaxy?
  15. What is the most distant object known to us in December, 1996?
  16. Would a nebula look colorful if you traveled into it?
  17. Where can I get a picture showing what the sky looks like with just galaxies present?
  18. Where can I get a photograph showing only the locations of galaxies in the sky, and not stars?
  19. How do we really know what the Milky Way looks like?
  20. What is the nearest nebula to the Earth?
  21. What does the Milky Way look like at other wavelengths than optical light?
  22. What is dark matter made of?
  23. What do we know about the 'Great Annihilator' in the center of the Milky Way?
  24. The quasar PKS 0405-385 was discovered to be a gamma ray source. What is the implication for the origin of gamma ray bursts?
  25. What is the Lyman Alpha Forest?
  26. What is the diameter of the giant elliptical galaxy Messier 87 in Virgo?
  27. Why are there barred spiral galaxies?
  28. What is the Great Wall?
  29. What is the youngest galaxy that astronomers have seen so far?
  30. Why is it so hard to detect carbon monoxide in irregular galaxies?
  31. Where can I get a 3-D map of the universe showing the nearest galaxies and clusters?
  32. If quasars are more distant than galaxies, how can their host galaxies still be host galaxies?
  33. Where can I get a map of the Sun's neighborhood in the Milky Way out to 200 light years?
  34. How many galaxies are there?
  35. What is the Milky Way made of?
  36. What would the Milky Way look like from outside?
  37. What are the most distant objects in the universe?
  38. What is so interesting about the galaxy Dwingeloo 1?
  39. Do galaxies tend to get aligned with each other in clusters of galaxies?
  40. If the universe were the size of the Earth, how big would the Milky Way be?
  41. Do galaxies affect each other gravitationally?
  42. Have molecules been found in space?
  43. Why are some galaxies pinwheel-shaped and others not?
  44. Is it true that there are a million galaxies behind every square inch of the night sky?
  45. Is our Milky Way flat?
  46. Which galaxies are closest to the Milky Way?
  47. What fraction of hydrogen in the interstellar medium is atomic, ionized or molecular?
  48. Where can I find an on-line NGC catalog?
  49. Could you explain how gravitational lenses work, and what determines the number of images you see?
  50. In the expanding universe, space is said to be expanding while at the same time galaxies are not moving. Isn't this a contradiction?
  51. What is a galaxy?
  52. Exactly how many stars are there in the Milky Way?
  53. How long did it take an object now 10 billion light years away to get there since the Big Bang?
  54. How do astronomers measure the distances to far away galaxies?
  55. What happens when galaxies collide?
  56. Do the arm spacings of spiral galaxies follow the Fibonacci Series?
  57. Have astronomers discovered two galaxies that are exciting for cosmology?
  58. What are spiral density waves made of?
  59. Can you give the names of astronomers who have theorized about quasars?
  60. Could a quasar be a star in our galaxy that is lasing?
  61. What is the evidence for Dark Matter in the Milky Way?
  62. Would the center pf the Milky Way be hostile to Earth-like planets?
  63. How often does the Sun pass through the spiral arm it was born in?
  64. If the Earth were at the center or outer edge of the Milk Way, what would the sky look like?
  65. Why are quasars so far away?
  66. Who discovered that the Milky Way rotates?
  67. Could galactic dark matter be black holes that formed before the Era of Nucleosynthesis?
  68. I saw a movie with two galaxies colliding on television.Was this an animation?
  69. Can astronomers determine the spectra of stars in other galaxies?
  70. If the Sun rotates around the center of the Milky Way, is the entire solar system moving around too?
  71. How many galaxies are there?
  72. If the Milky Way were the size of a penny, how big would the rest of the universe be?
  73. Independent of theory, how do we know there are galaxies millions of light years away?
  74. What happens inside clouds in space?
  75. What do the stars in the center of the Milky Way actually revolve around?
  76. How many galaxies are there in the universe?
  77. What would happen if you journeyed 33,000 light years through our spiral arm?
  78. Why do we call our galaxy the Milky Way and not something more technical?
  79. How long have quasars been around?
  80. What things do we not understand about the center of the Milky Way?
  81. What would a trip to the center of the Milky Way be like?
  82. Exactly how far from the center of the Milky Way is the Sun?
  83. Is there a nebula in the constellation Aquila that contains ethynol?
  84. Exactly how do astronomers estimate that there are 200 to 500 billion stars in the Milky Way?
  85. What happens if you move 33,000 light years along the Sun's spiral arm in the Milky Way?
  86. What constellation corresponds to our location in the Orion Spur?
  87. If you observed the Milky Way from a distant quasar, would it look like a quasar too?
  88. Does the gravitational field of the Milky Way tell us anything about dark matter?
  89. Is there a preferred plane of rotation for large numbers of galaxies in space?
  90. Are there galaxies that do not belong to clusters?
  91. Is life mor likely to be present in spiral galaxies or in elliptical galaxies?
  92. In what direction does the Milky Way rotate?
  93. Why do globular clusters form round, and galaxies form flat?
  94. Will we ever look so far into space that we will see baby pictures of the Milky Way?
  95. How well can we ever know what the universe looks like when we cannot see galaxies where they are right now?
  96. What is the most distant molecule known and why is this important?
  97. How do stars in distant quasars compare to those in our Milky Way?
  98. Are irregular galaxies old enough to have heavy elements like the disks of spiral galaxies?
  99. What is it that triggers a spiral density wave in a galaxy in the first place?
  100. If quasars are very young galaxies, how do they have supermassive black holes produced by evolved stars?
  101. How does a spiral galaxy avoid wrapping itself up into a big knot of stars?
  102. If non-zero rest mass particles can absorb light, why doesn't the dark matter halo around the Milky Way affect the cosmic background radiation?
  103. Are there any differences in the rotation speeds of Sa and Sc-type galaxies?
  104. If there really is dark matter in the universe, why don't we see more gravitational lenses all around us?
  105. Does carbon monoxide contribute the same to forming stars in spiral and irregular galaxies?
  106. If the Milky Way were 1 meter across, how big would the rest of the universe be?
  107. Do all galaxies have names?
  108. How far away is the Draco System?
  109. If we live in a closed universe, could some of the distant galaxies we see just be images of the Milky Way?
  110. Is there a black hole at the center of the Milky Way?
  111. How many different kinds of galaxy types are there?
  112. Where can I get catalogs of the different kinds of objects in the distant universe?
  113. What is the most distant molecule yet observed?
  114. Why is the Milky Way called by so many different names?
  115. How do astronomers know that the sun is located 50 parsecs above the plane of the Milky Way?
  116. Is there anything interesting about the Sun's location in the Milky Way?
  117. Are there atoms and molecules in other galaxies?
  118. How do astronomers figure out the distance to the center of the Milky Way?
  119. What is inside the nucleus of a galaxy?
  120. Could quasars be powered by anti-matter?
  121. What fraction of the stars in our galaxy are red giants, white dwarfs etc?
  122. Is our galaxy a typical shape for galaxies in the universe?
  123. Do galaxies form the same way that eddies and whirlpools form in the wake of a boat?
  124. What are spiral density waves?
  125. Why aren't there anti-matter galaxies out there in space?
  126. Do magnetic fields exist throughout space?
  127. Why do some galaxies have two or more catalog names?
  128. What is at the center of our galaxy?
  129. Do galaxies form clusters and strings?
  130. Are the spaces between galaxies filled with stars or gas?
  131. How many galaxies are the result of collisions and mergers?
  132. What the ding dang is a quasar?
  133. How far from the center of the universe is our galaxy?
  134. If the universe is infinite, then its total mass should be zero. Does this mean there is negative mass to cancel out the positive mass found in stars and galaxies?
  135. If a galaxy is 10 billion light years away, with the expansion, did it take light 10 billion years to get here?

RETURN to the Question and Answer Index.