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Physics, Astronomy & Cosmology / Re: Are all the planets in the solar system the same age?
« on: 13/02/2019 08:33:03 »
The Solar System formed by a cloud of gas and dust contracting under its own gravitational field.
- It is a positive feedback system, in that the more the gas contracts, the more intense its gravitational field, so the more it contracts...
- This contraction is opposed by conservation of momentum, which tends to keep the gas in an orbit around the center of mass, rather than converging on the center of mass
- This orbiting gas is opposed by the many random directions of patches of the orbiting gas, which collide with each other, heating up. The increased temperature also opposes contraction.
- This excess temperature is radiated more easily if there are heavier elements mixed in (from carbon to iron), as a result of previous supernovas seeding the dust cloud with heavier elements
- The collisions cancel out different angular momentum, dumping gas closer to the center (which eventually forms the star)
- While some gas remains on the outskirts of a flattish disk, forming the planets
- This protoplanetary disk has been observed by radiotelescopes
So the whole gravitational collapse thing happens together - you don't need the Sun to form first.
- In fact, the orbit of a Jupiter-sized object is determined by the mass within its orbit
- It doesn't matter whether that mass is compact or fuzzy
- or whether it is fusing hydrogen or not
See: https://www.almaobservatory.org/en/press-release/almas-best-image-of-a-protoplanetary-disk/
https://en.wikipedia.org/wiki/Protoplanetary_disk
- It is a positive feedback system, in that the more the gas contracts, the more intense its gravitational field, so the more it contracts...
- This contraction is opposed by conservation of momentum, which tends to keep the gas in an orbit around the center of mass, rather than converging on the center of mass
- This orbiting gas is opposed by the many random directions of patches of the orbiting gas, which collide with each other, heating up. The increased temperature also opposes contraction.
- This excess temperature is radiated more easily if there are heavier elements mixed in (from carbon to iron), as a result of previous supernovas seeding the dust cloud with heavier elements
- The collisions cancel out different angular momentum, dumping gas closer to the center (which eventually forms the star)
- While some gas remains on the outskirts of a flattish disk, forming the planets
- This protoplanetary disk has been observed by radiotelescopes
So the whole gravitational collapse thing happens together - you don't need the Sun to form first.
- In fact, the orbit of a Jupiter-sized object is determined by the mass within its orbit
- It doesn't matter whether that mass is compact or fuzzy
- or whether it is fusing hydrogen or not
See: https://www.almaobservatory.org/en/press-release/almas-best-image-of-a-protoplanetary-disk/
https://en.wikipedia.org/wiki/Protoplanetary_disk
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