Formation and evolution of the Solar System
There is evidence that the formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed.
Artist's conception of a protoplanetary disk
Pierre-Simon Laplace, one of the originators of the nebular hypothesis
Hubble image of protoplanetary discs in the Orion Nebula, a light-years-wide stellar nursery probably very similar to the primordial nebula from which the Sun formed
Meteor Crater in Arizona. Created 50,000 years ago by an impactor about 50 metres (160 ft) across, it shows that the accretion of the Solar System is not over.
The Solar System is the gravitationally bound system of the Sun and the objects that orbit it. It was formed 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc. The Sun is an ordinary main sequence star that maintains a balanced equilibrium by the fusion of hydrogen into helium at its core, releasing this energy from its outer photosphere.
Montage of the largest bodies in the Solar System. The asteroid belt and Kuiper belt are not added because the individual asteroids are too small to be shown.
Diagram of the early Solar System's protoplanetary disk, out of which Earth and other Solar System bodies formed
A diagram depicting the habitable zone boundaries around stars, and how the boundaries are affected by star type.
The Sun in true white color
