The Oort Cloud is a spherical cloud of transneptunian objects that lies at the limits of the Solar System, almost one light year from Sun and about a quarter the distance from the Sun to Proxima Centauri, the closest star to our Solar System. The other two known accumulations of transneptunian objects, the Kuiper Belt and the Scattered Disc, are located about one hundred times closer to the Sun than the Oort Cloud. According to some statistical estimates, the cloud could hold between one and a hundred trillion (1012 - 1014) objects, its mass being about five times that of Earth. It has two different regions: the outer Oort Cloud, spherical in shape, and the inner Oort Cloud, also called the Hills cloud, in the shape of a disc. Oort Cloud objects are believed to be made up of compounds such as ice, methane, and ammonia, among others, and formed very close to the Sun when the Solar System was still in its early stages of formation. Once formed, they reached their current position in the Oort Cloud due to the gravitational effects of the giant planets. The Oort Cloud is considered the origin of the majority of the comets of the Solar System.
