Formation of the Stars and Their Planets

Abstract

Where did the Sun and its attendant planets come from? How and when did they form? The most likely explanation is provided by the nebular hypothesis, which states that the Sun and planets formed together, as a result of the gravitational collapse of an interstellar cloud of gas and dust also known as the solar nebula. This theory accounts for the orderly aligned motions of the major planets. They all move in a narrow band across the sky, implying that their orbits all lie in nearly the same plane, which nearly coincides with the Sun’s equatorial plane. All of the planets move in the same direction within their Sun-centered orbits, and both the Sun and most of the major planets rotate in this direction – Venus and Uranus are the exceptions.