114 FAQs about our Solar System (The Astronomy Cafe)

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

Beginner:

  1. What are the atmospheric constituents of the outer planets?
  2. Can a planet ever explode?
  3. Are all planets round?
  4. Does any moon in our solar system also have a moon?
  5. Which planet is hottest, Venus or Mercury?
  6. What size defines a planet,comet,asteroid or moon?
  7. What are moons made of?
  8. How bright would it be to stand on the surfaces of each of the planets?
  9. Where are the highest winds in the solar system found?
  10. In which direction do planets rotate?
  11. What are the three largest moons in the solar system?
  12. Is our solar system typical?
  13. What are the mean surface temperatures of the planets?
  14. Why doesn't every planet have a ring?
  15. What are the masses of the satellites of Mars?
  16. Do the giant planets like Jupiter have solid surfaces?
  17. Why don't Mercury and Venus have moons?
  18. Is there any truth to the hypothesis that Pluto is a comet not a true planet?
  19. Why are planets round and not some other shape?
  20. Is there any evidence for chaotic motion in the solar system?
  21. At what times are the planets closest and farthest from the Sun?
  22. Will other planets ever collide with the Earth?
  23. What are the speeds of the planets in their orbits?
  24. What is the Ecliptic?
  25. How fast does light travel from the Sun to each of the planets?
  26. What is the relationship between the plane of the solar system and the plane of the Milky Way?
  27. Is our solar system moving in orbit around another star?
  28. Have any new asteroids or other objects been found outside the orbit of Neptune?
  29. Why isn't there more 'junk' inside the orbit of the Earth from failed moons of Venus and Mercury?
  30. Have astronomers discovered other bodies orbiting the Earth or Moon?
  31. If the orbits of Neptune and Pluto intersect, will they ever collide?
  32. How are planets formed?
  33. Why do the planets orbit the Sun in the same plane?
  34. How often do planetary alignments occur?
  35. When will Mercury or Venus pass in front of the Sun?
  36. When was the last time a 'May 5, 2000' conjunction occurred?
  37. During the last 25 years, when were Mars and Earth closest?
  38. Did the universe somehow align itself on March 9, 1920?
  39. Will there be a planetary alignment on May 5, 2000 that will devastate the world?
  40. The 'Millenium' TV program claims that terrible things will happen on May 5, 2000. Is this true?
  41. Were all 8 planets in the daytime sky on 23 August 1946 from San Antonio, Texas?
  42. Was there a planetary conjunction on 12/27/1986?
  43. Is it true that Venus, Mars and Jupiter will be very close together in the sky in the year 2015?
  44. Where did the idea come from that something bad was going to happen on May 5, 2000?
  45. Do the Moon, Venus and Orion ever come into alignment?
  46. Have planets ever been observed to eclipse one another in the sky?
  47. Will there be global flooding caused by upcoming planetary conjunctions?
  48. What was the 'harmonious conjunction' that happened back in 1987?
  49. What is the most distant planet you can see with the naked eye?
  50. What is the most spectacular planetary conjunction in the past or the future?
  51. Is it possible for all the planets to line up in the solar system, and what would happen?
  52. Can you define conjunction and opposition?
  53. Have any spectacular phenomena ever been seen in the solar system in recent history?
  54. Is there a nemonic for remembering the ordering of the planets in the solar system?
  55. Would you see stars in the daytime on the Moon and Mars?
  56. If Jupiter had become a star, what would the solar system look like?
  57. Does there exist life on other planets in our solar system?
  58. How much of the mapable area of the solar system has in fact been mapped?
  59. If the Sun were one meter across, what would be the relative sizes of the planets and their orbits?
  60. Where did the symbol for the Earth originate?
  61. Can you terraform a planet to make it like the Earth?
  62. How fast do you have to go to get to outer space?
  63. What percent of the mass of the solar system is in the Sun?
  64. If sunlight on the Earth equalled a 100 watt bulb, how big a bulb would you get on Jupiter?
  65. What would happen if all the planets really lined up?
  66. Is there a simple observation that proves the Earth goes around the Sun?
  67. Is the proof that the Earth goes around the Sun too difficult to confirm observationally?
  68. Did the planets form in the orbits that they are now in?
  69. When the Sun becomes a red giant star, what will happen to the outer planets and their satellites?
  70. Just how crowded is the asteroid belt?
  71. COuld there be another planet in Earth's exact orbit, but behind the Sun?

Intermediate:

  1. What are the surface gravitational accelerations for the planets?
  2. What are the atmospheric constituents of the outer planets?
  3. How much energy do the planets each get from the Sun compared to the Earth?
  4. Why are the atmospheres of Venus, Earth and Mars so different?
  5. Why do Venus, Uranus and Pluto have retrograde rotation?
  6. How do astronomers estimate the ages for the planets?
  7. What are the element abundances for the solar system, Earth and Moon?
  8. Are the atmospheres of the planets potentially explosive?
  9. Where do planetary rings come from?
  10. Do the giant planets have similar internal structure?
  11. Where do the planetary moons come from?
  12. Does the solar system have a barycenter?
  13. Could you explain what Kepler's Laws are all about in a simple way?
  14. If planets travel in elliptical orbits with the Sun at one focus, what happens at the other focus?
  15. Why is the asteroid belt considered a planet that never formed, rather than one that broke up?
  16. How old are the Sun, Moon and Earth?
  17. What is the relationship between star formation in nebulae, and planet formation?
  18. Why were the terrestrial and gaseous planets formed so differently?
  19. Why don't planetary alignments affect the Earth?
  20. When will Mercury or Venus pass in front of the Sun?
  21. Can the gravitational pulls of the planets in conjunction cause earthquakes?
  22. The 'Millenium' TV program claims that terrible things will happen on May 5, 2000. Is this true?
  23. What is synodic time?
  24. If you swapped the Moon and Mercury, what would be the repercussions?
  25. Does there exist life on other planets in our solar system?
  26. If the Sun were to be taken away, how would the orbit of the earth change?
  27. Where did the symbol for the Earth originate?
  28. How do we really know that the Copernican model is the correct one?
  29. Why do astronomers believe that the Oort Cloud exists?
  30. Could you explain in some detail how we think planets form?
  31. What percent of the mass of the solar system is in the Sun?
  32. What makes gas and rocks clump together to make stars and planets?
  33. 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. Are all planets round?
  4. How many stars have contributed to producing the heavy elements in our solar system?
  5. Why do planets move along elliptical paths and not circular orbits?
  6. How was the solar system formed? (Part I)
  7. How was the solar system formed? (Part II)
  8. How many generations of stars were needed to create the heavy elements in our solar system?

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