Bintang yang menyerupai matahari biasanya memakan waktu sekitar juta tahun untuk terbentuk. Cakram protoplanet merupakan piringan akresi yang melanjutkan untuk memberi makan bintang pusat.
Cakram ini awalnya sangat panas, yang kemudian mendingin yang dikenal sebagai tahap bintang T Tauri, di sini dimungkinkan terbentuknya butiran-butiran debu yang terbuat dari batu dan es. Butir-butiran ini akhirnya mengental menjadi planetisimal berukuran kilometer. Jika cakram berukuran cukup besar proses pertumbuhan bisa dimulai dengan sangat cepat, dalam waktu Di dekat bintang, embrio planet melewati tahap penggabungan, menghasilkan beberapa planet kebumian.
Tahap terakhir memakan waktu sekitar juta sampai satu miliar tahun. Pembentukan planet raksasa merupakan proses yang lebih rumit. Proses ini diduga terjadi di luar garis beku, di mana embrio planet umumnya terbuat dari beragam es.
Akibatnya mereka beberapa kali lebih besar dibandingkan yang terbentuk di bagian dalam piringan protoplanet. Apa yang terjadi setelah pembentukan embrio planet belum sepenuhnya diketahui. Namun, beberapa embrio terus tumbuh dan akhirnya mencapai kali massa Bumi.
There was abundant hydrogen, carbon, oxygen, nitrogen, and less silicon and iron, giving the outer planets more building material. Second, the stronger gravitational pull of these giant planets allowed them to collect large quantities of hydrogen and helium, which could not be collected by the weaker gravity of the smaller planets. These collisions created the asteroid belt, an unfinished planet, located between Mars and Jupiter.
This asteroid belt is the source of most meteorites that currently impact the Earth. Study of asteroids and meteorites help geologist to determine the age of Earth and the composition of its core, mantle, and crust.
The outermost part of the solar system is known as the Kuiper belt, which is a scattering of rocky and icy bodies. Beyond that is the Oort cloud, a zone filled with small and dispersed ice traces. These two locations are where most comets form and continue to orbit, and objects found here have relatively irregular orbits compared to the rest of the solar system.
Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Astronomy Terms. Nebular Hypothesis. Cite This! Try Our Sudoku Puzzles! The temperature, reaction rate, pressure, and density increased until hydrostatic equilibrium was achieved. At this point, the Sun became a main-sequence star. Solar wind from the Sun created the heliosphere and swept away the remaining gas and dust from the protoplanetary disc into interstellar space, ending the planetary formation process. The idea that the Solar System originated from a nebula was first proposed in by Swedish scientist and theologian Emanual Swedenborg.
In this treatise, he argued that gaseous clouds nebulae slowly rotate, gradually collapsing and flattening due to gravity and forming stars and planets.
A similar but smaller and more detailed model was proposed by Pierre-Simon Laplace in his treatise Exposition du system du monde Exposition of the system of the world , which he released in As the cloud spun more rapidly, it threw off material that eventually condensed to form the planets. The Laplacian nebular model was widely accepted during the 19th century, but it had some rather pronounced difficulties. The main issue was angular momentum distribution between the Sun and planets, which the nebular model could not explain.
In addition, Scottish scientist James Clerk Maxwell — asserted that different rotational velocities between the inner and outer parts of a ring could not allow for condensation of material. By the early 20th century, the Laplacian model had fallen out of favor, prompting scientists to seek out new theories. However, it was not until the s that the modern and most widely accepted variant of the nebular hypothesis — the solar nebular disk model SNDM — emerged. Credit for this goes to Soviet astronomer Victor Safronov and his book Evolution of the protoplanetary cloud and formation of the Earth and the planets In this book, almost all major problems of the planetary formation process were formulated and many were solved.
For example, the SNDM model has been successful in explaining the appearance of accretion discs around young stellar objects. Various simulations have also demonstrated that the accretion of material in these discs leads to the formation of a few Earth-sized bodies.
Thus the origin of terrestrial planets is now considered to be an almost solved problem. While originally applied only to the Solar System, the SNDM was subsequently thought by theorists to be at work throughout the Universe, and has been used to explain the formation of many of the exoplanets that have been discovered throughout our galaxy.
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