The central region collapsed due to gravity to become the Sun , while the rest of the disk went on to form the planets, comets and asteroids . Planet formation began with the grains of dust and ice colliding and sticking together to form larger objects. We are using computer simulations to study how these larger objects accreted one another to form planets and asteroids. Here are some examples of planetary systems produced by the computer simulations. All forms of life on Earth require liquid water to survive, so the presence of liquid water is a good criterion for deciding whether other planets in the universe could be habitable.
Earth is the only habitable planet in the solar system.
Venus, closer to the Sun, is too hot to have liquid water. Planets and moons in the outer solar system are too cold for liquid water. In between is a Habitable Zone , where any large, rocky planet should be habitable. Mars lies inside the habitable zone, but it is too small to have a thick atmosphere or liquid water. Here are 7 planetary systems generated using the computer simulations described above.