![]() The giant planets (Jupiter, Saturn, Uranus, and Neptune) formed further out, beyond the frost line, the point between the orbits of Mars and Jupiter where material is cool enough for volatile icy compounds to remain solid. Because metallic elements only comprised a very small fraction of the solar nebula, the terrestrial planets could not grow very large. ĭue to their higher boiling points, only metals and silicates could exist in solid form in the warm inner Solar System close to the Sun, and these would eventually form the rocky planets of Mercury, Venus, Earth, and Mars. Hundreds of protoplanets may have existed in the early Solar System, but they either merged or were destroyed or ejected, leaving the planets, dwarf planets, and leftover minor bodies. ![]() The planets formed by accretion from this disc, in which dust and gas gravitationally attracted each other, coalescing to form ever larger bodies. As the contracting nebula rotated faster, it began to flatten into a protoplanetary disc with a diameter of roughly 200 AU (30 billion km 19 billion mi) and a hot, dense protostar at the center. The center, where most of the mass collected, became increasingly hotter than the surrounding disc. As the region that would become the Solar System, known as the pre-solar nebula, collapsed, conservation of angular momentum caused it to rotate faster. As is typical of molecular clouds, this one consisted mostly of hydrogen, with some helium, and small amounts of heavier elements fused by previous generations of stars. This initial cloud was likely several light-years across and probably birthed several stars. The Solar System formed 4.568 billion years ago from the gravitational collapse of a region within a large molecular cloud. The nearest stars to the Solar System are within the Local Bubble the closest star is named Proxima Centauri and is at a distance of 4.2441 light-years away.Īrtist's impression of the early Solar System's protoplanetary disk, out of which Earth and other Solar System bodies formed The Oort cloud, which is thought to be the source for long-period comets, may also exist at a distance roughly a thousand times further than the heliosphere. The heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium it extends out to the edge of the scattered disc. The solar wind, a stream of charged particles flowing outwards from the Sun, creates a bubble-like region of the interplanetary medium in the interstellar medium known as the heliosphere. Many small-body populations, including comets, centaurs and interplanetary dust clouds, freely travel between the regions of the Solar System. There is consensus among astronomers to these nine objects as dwarf planets: the asteroid Ceres, the Kuiper-belt objects Pluto, Orcus, Haumea, Quaoar, and Makemake, and the scattered-disc objects Gonggong, Eris, and Sedna. These objects are distributed in the asteroid belt that lies between the orbits of Mars and Jupiter, the Kuiper belt, the scattered disc that both lies beyond Neptune's orbit and at even further reaches of the Solar System which they would be classified as an extreme trans-Neptunian object. There are an unknown number of smaller dwarf planets and innumerable small bodies orbiting the Sun. All giant planets and a few smaller bodies are encircled by planetary rings, composed of ice, dust and sometimes moonlets. Six planets, six largest possible dwarf planets and many other bodies have natural satellites or moons orbiting around them. In the present day, 99.86% of the Solar System's mass is in the Sun and most of the remaining mass is contained in the planet Jupiter. That is the reason why all eight planets have an orbit that lies near the same plane. Over time, the cloud formed the Sun and a protoplanetary disk that gradually coalesced to form planets and other objects. The Solar System was formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. In some texts, these terrestrial and giant planets are called the inner Solar System and outer Solar System planets respectively. The gas giants are mostly made of hydrogen and helium, while the ice giants are mostly made of ' volatile' substances such as water, ammonia, and methane. The terrestrial planets have a definite surface and are mostly made of rock and metal. ![]() The largest of such objects are the eight planets, in order from the Sun: four terrestrial planets named Mercury, Venus, Earth and Mars, two gas giants named Jupiter and Saturn, and two ice giants named Uranus and Neptune. The Solar System is the gravitationally bound system of the Sun and the objects that orbit the star. Invariable-to- galactic plane inclination
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