110 FAQs about Asteroids, Meteors and Comets (The Astronomy Cafe )

Basic Facts: NASA/NSSDC Fact Sheet, Near Earth Orbit Asteroids,Comets

Orbits and Discoveries: IAU Minor Planet Center , Trans-Neptunian Bodies

Pictures: Galileo Pictures,NEAR Pictures,Comet Images,Hubble Space Telescope

Impact Hazards and Extinctions: NASA/Ames Research Center

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

Beginner:
  1. [Updated]How are comets formed?
  2. [Updated]What is the difference between an asteroid, a comet and a meteorite?
  3. [Updated]What happens to a meteor when it hits the ground?
  4. [Updated]What are most asteroids made from?
  5. [Updated]Do asteroids have dust on them?
  6. [Updated]Why are asteroids made from rocks and not fluffy things since they were never inside something to remelt them?
  7. [Updated]Do all comets come from outside our solar system?
  8. [Updated]How fast do asteroids and comets rotate?
  9. [Updated]What would you do if there was a one week warning of an impending asteroid impact?
  10. [Updated]Will a rogue comet or asteroid ever hit Earth?
  11. [Updated]How fast do comets move?
  12. [Updated]Could an asteroid strike the Earth with little warning?
  13. Has anyone ever been hit by a meteor?
  14. What would happen if a large object hit the Earth?
  15. How big do comets get?
  16. Where in the Milky Way do comets captured in the Oort Cloud originate?
  17. Can a comet be larger than the Sun?
  18. Where can I get a list of all the known naked-eye comets?
  19. What is the difference between the Kuiper Cloud and the Oort Cloud?
  20. Where do short-period comets come from?
  21. What is a comet?
  22. Why don't comets get captured by planets when they come close?
  23. Is it true the Earth passes through the tail of Halley's Comet in 1910?
  24. How fast do the nuclei of comets rotate?
  25. How do you name a comet?
  26. Can you 'simulate' a comets nucleus in the laboratory?
  27. What is the brightest comet ever seen from the earth?
  28. What would the surface of Hale-Bopp look like up close?
  29. Will Earth pass through the tail of Comet Hale-Bopp?
  30. Could you say something about the 1997 comet Hale-Bopp?
  31. How many times in Earth's history has Halleys Comet appeared?
  32. Was anything peculiar seen in the tail of Comet Hyakutake?
  33. When was the last time we had two bright comets in the same year?
  34. Can you say anything about comet P/Wild 2?
  35. Did Mark Twain (1835-1910) really get born and die during the apparitions of Halley's Comet?
  36. When will Halley's comet return?
  37. Why do some comets emit gas and dust even when they are far from the Sun?
  38. Will Comet Swift-Tuttle collide with the Earth in 4000 AD?
  39. Will the asteroid 1981 Midas collide with the Earth in the 22nd century?
  40. Is the Pentagon planning to shoot down an asteroid soon?
  41. How do you tell if a rock is a meteorite?
  42. If I were to see a fireball in the sky, who should I report it to?
  43. Do any meteorites come from outside the solar system?
  44. How big are the particles we call 'Shooting Stars'?
  45. Why do some meteors produce smoke trails and others not?
  46. If I hear a sonic boom soon after seeing a fireball, how close could it have impacted to where I was standing?
  47. How do meteorites form in space?
  48. If meteors burn up in the Earth's atmosphere, where do they keep coming from?
  49. Which meteor shower is called the 'Tears of St. Lawrence' and why?
  50. How old is the Murchison Meteorite?
  51. How many meteors enter the Earth's atmosphere every day?
  52. What are fireballs and bolides, and how often can you see them?
  53. What does an impact created from a small meteor look like?
  54. Did the Earth almost get hit by an asteroid on March 23, 1989?
  55. What would the Cretaceous Impactor have looked like from the ground?
  56. Did the Yukatan Impact really kill the dinosaurs, and when will the next one happen?
  57. Which comet has come closest to the Earth?
  58. How much notice would we get from a asteroid like the one that hit Earth 65 million years ago?
  59. How should a near Earth asteroid be deflected?
  60. How could we protect the Earth against a deadly comet impact?
  61. If a comet was about to strike a heavily populated area, would the authorities try to hush it up to avoid panic?
  62. What building blocks for life could have come from asteroid impacts?
  63. Can the impact of a large comet or asteroid change the tilt of a planets rotation axis?
  64. How much actual mass is in the tail of a comet?
  65. Are meteorites worth anything?

Intermediate:
  1. [Updated]Why don't the ices in comets just sublimate away?
  2. Why do some comets have two tails?
  3. How are comet masses determined?
  4. Why are comets sometimes fainter their first time around the Sun than in subsequent passes?
  5. How do astronomers know that Comet Hyakutake has been around the Sun before?
  6. Can an asteroid have an atmosphere?
  7. Can you build an electronic meteor detector?
  8. Can a gigantic comets magnetism cause the Earth's poles to shift?
  9. Could a comet impact on Jupiter trigger thermonuclear fusion in its atmosphere?
  10. Why isn't the government doing more to protect us from deadly meteor impacts?
  11. What are the odds of the Earth being hit by an asteroid?

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