94 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

 Back to the Astronomy Cafe - 365 of the most popular questions since 1996. Over 1 million page requests!

 

Beginner:

  1. Does the Milky Way move in space or does it just stay put?
  2. Do all stars belong to galaxies?
  3. What are gamma ray bursts?"
  4. How many spiral arms does the Milky Way have?
  5. How do we know the Milky Way is a spiral galaxy?
  6. Would a nebula look colorful if you traveled into it?
  7. How do we really know what the Milky Way looks like?
  8. What is the nearest nebula to the Earth?
  9. What is the diameter of the giant elliptical galaxy Messier 87 in Virgo?
  10. Why are there barred spiral galaxies?
  11. What is the Great Wall?
  12. How many galaxies are there?
  13. What is the Milky Way made of?
  14. What would the Milky Way look like from outside?
  15. If the universe were the size of the Earth, how big would the Milky Way be?
  16. Is our Milky Way flat?
  17. Which galaxies are closest to the Milky Way?
  18. What is a galaxy?
  19. If the Earth were at the center or outer edge of the Milk Way, what would the sky look like?
  20. Who discovered that the Milky Way rotates?
  21. If the Milky Way were the size of a penny, how big would the rest of the universe be?
  22. How many galaxies are there in the universe?
  23. Why do we call our galaxy the Milky Way and not something more technical?
  24. What would a trip to the center of the Milky Way be like?
  25. Exactly how far from the center of the Milky Way is the Sun?
  26. Are there galaxies that do not belong to clusters?
  27. In what direction does the Milky Way rotate?
  28. If the Milky Way were 1 meter across, how big would the rest of the universe be?
  29. Do all galaxies have names?
  30. Is there a black hole at the center of the Milky Way?
  31. Are there atoms and molecules in other galaxies?
  32. What is inside the nucleus of a galaxy?
  33. Could quasars be powered by anti-matter?
  34. What fraction of the stars in our galaxy are red giants, white dwarfs etc?
  35. Why aren't there anti-matter galaxies out there in space?
  36. Do magnetic fields exist throughout space?
  37. Are the spaces between galaxies filled with stars or gas?

  38. When will the next galaxy hit the Milky Way?

  39. Who discovered the first galaxy?

  40. What is 'space dust'?

  41. If the Milky Way were the size of a coffee cup, how big would the rest of the universe be?

  42. What are the names of the spiral arms in our Milky Way?

  43. What is the farthest object we know about in the universe?

  44. What is a quasar?

  45. What gives galaxies their different shapes?

Intermediate:

  1. Are there any more big galaxies hidden behind the Milky Way in our Local Group?
  2. Where can I find a 3-D map of the Milky Way?
  3. How can amino acids such as Glycine exist under the harsh conditions of interstellar space?
  4. Are the properties inside 'Local Bubbles' the same everywhere?
  5. If all galaxies have black holes in their cores, why do some of them emit streams of particles in 'jets'?
  6. What does the Milky Way look like at other wavelengths than optical light?
  7. What is dark matter made of?
  8. What do we know about the 'Great Annihilator' in the center of the Milky Way?
  9. What is the youngest galaxy that astronomers have seen so far?
  10. Where can I get a 3-D map of the universe showing the nearest galaxies and clusters?
  11. If quasars are more distant than galaxies, how can their host galaxies still be host galaxies?
  12. Have molecules been found in space?
  13. Why are some galaxies pinwheel-shaped and others not?
  14. What fraction of hydrogen in the interstellar medium is atomic, ionized or molecular?
  15. Exactly how many stars are there in the Milky Way?
  16. What happens when galaxies collide?
  17. How often does the Sun pass through the spiral arm it was born in?
  18. What do the stars in the center of the Milky Way actually revolve around?
  19. How long have quasars been around?
  20. Exactly how do astronomers estimate that there are 200 to 500 billion stars in the Milky Way?
  21. If you observed the Milky Way from a distant quasar, would it look like a quasar too?
  22. Will we ever look so far into space that we will see baby pictures of the Milky Way?
  23. How do stars in distant quasars compare to those in our Milky Way?
  24. Are there atoms and molecules in other galaxies?
  25. What is inside the nucleus of a galaxy?
  26. Could quasars be powered by anti-matter?
  27. What fraction of the stars in our galaxy are red giants, white dwarfs etc?
  28. Why aren't there anti-matter galaxies out there in space?
  29. Do magnetic fields exist throughout space?

  30. If a galaxy is 10 billion light years away, with the expansion, did it take light 10 billion years to get here?

  31. How bright would the center of the Milky Way be without interstellar dust?

  32. What would happen if a gamma ray burst exploded near the sun?

  33. What happens when two galaxies collide?

  34. What chemicals have been detected in space?

  35. Why are there so many estimates for the number of stars in the Milky Way?

  36. What is the 'anti-matter fountain' all about?

  37. What do we know about quasars?

  38. How are the distances to galaxies measured?

  39. Is our Milky Way as old as some of the proto-galaxies seen in the Hubble Deep Field photograph?

Advanced:

  1. Where do the jets in active galactic nuclei come from?
  2. What is the Lyman Alpha Forest?
  3. In the expanding universe, space is said to be expanding while at the same time galaxies are not moving. Isn't this a contradiction?
  4. How do astronomers measure the distances to far away galaxies?
  5. What are spiral density waves made of?
  6. What is the evidence for Dark Matter in the Milky Way?
  7. Could galactic dark matter be black holes that formed before the Era of Nucleosynthesis?
  8. What is it that triggers a spiral density wave in a galaxy in the first place?
  9. How does a spiral galaxy avoid wrapping itself up into a big knot of stars?
  10. How do astronomers know that the sun is located 50 parsecs above the plane of the Milky Way?

RETURN to the Question and Answer Index.