Physics, Astronomy & Cosmology / Re: why are some heavenly bodies tilted on their axis and not others?« on: 24/07/2019 15:17:36 »
Quote from: alancalverd
Our moon does not appear to spin when seen from earth because it seems to be a chunk of Earth thrown off by some explosion or collisionUranus has an axial tilt of 82°.
Some suggest that this may have been due to a significant impact on the planet.
other planets spin and orbit in pretty random orientations relative to ours.It is thought that stars and their planetary systems form from an accretion disk.
- This accretion disk ends up with the net angular momentum of the part of the gas cloud from which they formed.
- So the star and the planets end up with roughly the same orbital axis.
In turn, the planets and their moons form from this same disk, and are likely to have a spin axis parallel to the planetary system as a whole.
- However, over time, influences of other planets can tilt the spin axis quite a lot; some astronomers suggest that the axis of Mars has changed significantly over time
- The Earth's axis has been somewhat stabilised by the large Moon, but it still changes a bit due to the Milankovitch cycles.
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