Do all planets go the same way round every sun? If so why?
Discussion
All the planets do, although there are variations in their plane (tilt) and shape of orbit (some are more circular than others).
Some comets and moons do rotate in the opposite direction (retrograde) which is probably due to various factors involved in how they came to be solar system members in the first place i.e. they may not have been part of the original spinning disk out of which most bodies of the solar system were formed.
Alternatively, a body can end up in a retrograde orbit if it has had a traumatic event early in its life - such as a major collision knocking it off its original more conventional path.
Some comets and moons do rotate in the opposite direction (retrograde) which is probably due to various factors involved in how they came to be solar system members in the first place i.e. they may not have been part of the original spinning disk out of which most bodies of the solar system were formed.
Alternatively, a body can end up in a retrograde orbit if it has had a traumatic event early in its life - such as a major collision knocking it off its original more conventional path.
One of the more intriguing questions is that of the hypothesis of Planet Nine.
Current theories have planets form out of the same accretion disc that the central star. This disc spins which gives the planets their initial motion; generally in the same direction as the spin of the star.
Eric's correct, a catastrophic event can cause a planet's orbit to become more eccentric, to tilt, and if the tilt goes far enough, to orbit backwards (retrograde).
None of the solar system's planets are retrograde. However, retrograde exoplanets (those around other stars) have been discovered; WASP-17b, HAT-P-7b and a few others. The Rossiter-McLaughlin effect is particularly useful at spotting these.
Eric's correct, a catastrophic event can cause a planet's orbit to become more eccentric, to tilt, and if the tilt goes far enough, to orbit backwards (retrograde).
None of the solar system's planets are retrograde. However, retrograde exoplanets (those around other stars) have been discovered; WASP-17b, HAT-P-7b and a few others. The Rossiter-McLaughlin effect is particularly useful at spotting these.
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