114 FAQs about our Solar System (The Astronomy Cafe)

Stardate Online, Planet Viewer , Solar System Today , Planetary Surface Maps

JPL Solar System Simulator, Image and Fact Browser,

Planet Positions Today, JPL Welcome to the Planets Guide,

Bill Arnett's Nine Planets Guide , JPL Planetary Photo Archive

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

Beginner:
  1. [Updated]Can a planet ever explode?
  2. [Updated]Is there any evidence for chaotic motion in the solar system?
  3. [Updated]How often do planetary alignments occur?
  4. [Updated]Why dont Venus and Mercury transit the sun every year?
  5. [Updated]Do the phases of Venus have to do with the shadow of Mercury?
  6. [Updated]How many moons do each of the planets in our solar system have?
  7. [Updated]Which objects in our solar system have magnetic fields?
  8. [Updated]Why are the magnetic and rotation axis of the planets never lined up?
  9. [Updated]Will other planets ever collide with Earth?
  10. [Updated]What causes massive planets to form instead of brown dwarf stars?
  11. [Updated]How far does the solar system extend around the sun?
  12. [Updated]What makes gas and rock clump together to make planets?
  13. [Updated]Have any new planets been discovered in our solar system?
  14. [Updated]Is our solar system typical of other planetary systems we know about?
  15. [Updated]On which planets would it be possible to live?
  16. At what times are the planets closest and farthest from the Sun?
  17. How fast does light travel from the Sun to each of the planets?
  18. What are the atmospheric constituents of the outer planets?
  19. Are all planets round?
  20. Which planet is hottest, Venus or Mercury?
  21. What size defines a planet,comet,asteroid or moon?
  22. How bright would it be to stand on the surfaces of each of the planets?
  23. Where are the highest winds in the solar system found?
  24. In which direction do planets rotate?
  25. What are the three largest moons in the solar system?
  26. What are the mean surface temperatures of the planets?
  27. Why doesn't every planet have a ring?
  28. What are the masses of the satellites of Mars?
  29. Do the giant planets like Jupiter have solid surfaces?
  30. Why don't Mercury and Venus have moons?
  31. Why are planets round and not some other shape?
  32. What are the speeds of the planets in their orbits?
  33. What is the relationship between the plane of the solar system and the plane of the Milky Way?
  34. Why isn't there more 'junk' inside the orbit of the Earth from failed moons of Venus and Mercury?
  35. Have astronomers discovered other bodies orbiting the Earth or Moon?
  36. If the orbits of Neptune and Pluto intersect, will they ever collide?
  37. How are planets formed?
  38. Why do the planets orbit the Sun in the same plane?
  39. When will Mercury or Venus pass in front of the Sun?
  40. Will there be a planetary alignment on May 5, 2000 that will devastate the world?
  41. Where did the idea come from that something bad was going to happen on May 5, 2000?
  42. The 'Millenium' TV program claims that terrible things will happen on May 5, 2000. Is this true?
  43. Is it true that Venus, Mars and Jupiter will be very close together in the sky in the year 2015?
  44. Do the Moon, Venus and Orion ever come into alignment?
  45. Have planets ever been observed to eclipse one another in the sky?
  46. Will there be global flooding caused by upcoming planetary conjunctions?
  47. What was the 'harmonious conjunction' that happened back in 1987?
  48. What is the most spectacular planetary conjunction in the past or the future?
  49. Is it possible for all the planets to line up in the solar system, and what would happen?
  50. Have any spectacular phenomena ever been seen in the solar system in recent history?
  51. Would you see stars in the daytime on the Moon and Mars?
  52. Does there exist life on other planets in our solar system?
  53. If the Sun were one meter across, what would be the relative sizes of the planets and their orbits?
  54. Where did the symbol for the Earth originate?
  55. Can you terraform a planet to make it like the Earth?
  56. How fast do you have to go to get to outer space?
  57. What percent of the mass of the solar system is in the Sun?
  58. If sunlight on the Earth equalled a 100 watt bulb, how big a bulb would you get on Jupiter?
  59. What would happen if all the planets really lined up?
  60. Did the planets form in the orbits that they are now in?
  61. When the Sun becomes a red giant star, what will happen to the outer planets and their satellites?
  62. Just how crowded is the asteroid belt?
  63. Could there be another planet in Earth's exact orbit, but behind the Sun?

Intermediate:
  1. [Updated]Why is the asteroid belt considered a planet that never formed, rather than one that broke up?
  2. [Updated]Where do the planetary moons come from?
  3. What are the surface gravitational accelerations for the planets?
  4. What are the atmospheric constituents of the outer planets?
  5. How much energy do the planets each get from the Sun compared to the Earth?
  6. Why are the atmospheres of Venus, Earth and Mars so different?
  7. Why do Venus, Uranus and Pluto have retrograde rotation?
  8. What are the element abundances for the solar system, Earth and Moon?
  9. Where do planetary rings come from?
  10. Do the giant planets have similar internal structure?
  11. Does the solar system have a barycenter?
  12. If planets travel in elliptical orbits with the Sun at one focus, what happens at the other focus?
  13. How old are the Sun, Moon and Earth?
  14. Why were the terrestrial and gaseous planets formed so differently?
  15. Why don't planetary alignments affect the Earth?
  16. When will Mercury or Venus pass in front of the Sun?
  17. Can the gravitational pulls of the planets in conjunction cause earthquakes?
  18. What is synodic time?
  19. Does there exist life on other planets in our solar system?
  20. If the Sun were to be taken away, how would the orbit of the earth change?
  21. How do we really know that the Copernican model is the correct one?
  22. Why do astronomers believe that the Oort Cloud exists?
  23. Could you explain in some detail how we think planets form?
  24. What makes gas and rocks clump together to make stars and planets?
  25. Do all the planets have magnetic poles like the Earth?

Advanced:
  1. How do astronomers weigh the planets?
  2. How are planetary magnetic fields produced?
  3. How many stars have contributed to producing the heavy elements in our solar system?
  4. How was the solar system formed? (Part I)
  5. How was the solar system formed? (Part II)

Return to Ask the Astronomer