Is there a reason the Gas Giants are further away from the sun that most terrestrial planets or is it a coincidence?
In: Planetary Science
While there are many theories about how the solar system formed, the most commonly accepted ones these days all agree that the planets most likely did not form exactly where they are. They disagree on exactly when they moved, or where exactly they came from, but some form of “migration” is the only way to explain data we’ve collected about the general composition of the planets.
Many of these models involve the gas giants forming much closer towards the sun. As their orbits adjusted, they ended up in what’s called an orbital “resonance,” meaning several large planets ended up repeatedly close to each other in their orbits. This may have effectively slingshot-launched some of them outwards into much further orbits, and may have actually ejected some planets from the solar system entirely.
This kind of movement is not far-fetched: we now believe that at some point, a Mars-sized planet was flung into Earth, and the impact debris later formed the moon. And many planets show a later period of sudden, intense crater formation and collisions all around the same time, a period known as the Late Heavy Bombardment. Circumstantial evidence at best, but still suspicious.
It was generally believed until relatively recently that gas giants cannot form closer due to the solar wind — a claim that many comments here are repeating. This was a tidy explanation, until we got more data about planet composition and started looking at other star systems in the past few decades. This has since been proven false. Looking out across the universe, we find that gas giants that orbit much closer to their stars are actually quite common, and rocky planets often orbit much further out.
Again, whether this is just a product of the many different ways that planets can form initially, or whether some kind of later “migration” is common throughout the universe, is still unknown.
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