L> Astronomy Lecture Notes - Solar System Formation Formation of the Solar System Main goal: Understand the reason for the various sizes, compositions, and also orbital and rotational motions of planets (Terrestrial, Jovian) and also minor objects (Pluto and comparable objects, asteroids, comets), including exceptions to the basic trends. The theory have to produce a scenario equivalent to the one for various other stellar devices. Stages of Star System Formation Starting point: A cloud of interstellar gas and also dust, the "solar nebula"; Many of it (98%) is hydrogen and helium, but it contains atoms and also dust grains of heavier material, created in previous generations of stars. Oncollection of formation: The nebula is currently thicker than the average interstellar region, and maybe component of a chaotic area of starbirth; Since of some disturbance that compresses it, such as a supernova explosion, it starts a gradual procedure of collapse. Contraction: The cloud starts collapsing under its own gravity; over 100,000 years, it shrinks dvery own to 100 AU, heats up (thermal energy), and also compresses in the facility. Accretion disk: The matter approximately the center spins up and also flattens into a disk, while heat vaporizes the dust. Protostar: Forms in the facility, when the core becomes opaque; later on will certainly end up being the Sun. (The gas orbiting the protostar in some instances may begin to compress under its own gravity, creating a twin star.) Condensation: The disk radiates amethod its power and also cools off; some gas condenses right into tiny dust grains of metal, rock and, much sufficient from the creating star, outside the "snow line", ice (differentiation). Planetesimals: Dust grains stick to each other (ice helps) and sweep their courses, creating larger particles; this accretion goes on until the particles end up being the dimension of boulders or tiny asteroids, which tempt matter through their gravity. Protoplanets: The bigger particles" expansion increases, and also they accumulate all of the solid issue close to their own orlittle bit. In 100,000 to 20,000,000 yr, the protoplanets" dimension is big asteroid/lunar size in the inner solar device, and also a number of times the Earth"s dimension in the external solar system (reduced temperature). Question: What is the relative prominence of gravitational instabilities and also core accretion in the formation process for gas giants? Solar wind: After about 1,000,000 yr, it sweeps amethod the leftover gas. If a protoworld is currently large sufficient, its gravity pulls in the bordering gas, and also it becomes a gas gigantic (leftover gas and dust around it condenses into moons); if not, it remains a rocky or icy body. Fragmentation: In 10 to 100 million years, while bigger planetesimals end up being more massive, smaller ones break right into smaller pieces when they collide, finish up as meteorites on larger objects, and/or their orbits are altered. Result Overview: After a billion years of clean-up and also meteoritic bombardment, you end up via ten or so planets, in secure orbits; The protostar turned into a star as soon as the core became warm enough. Catastrophes: Needed to define particular isolated functions and also exceptions. The planets, their surfaces and atmospheres may be heavily modified by the last, big collision they suffer. Examples: For Planet, our Moon and the visibility of water, carried by comets (the original Planet can not have preserved it); Also, composition of Mercury, Venus" rotation, Uranus" tilt. Debris: Some planetesimals remain in the asteroid belt (a would-be earth, if not for Jupiter) and the Kuiper belt; others are thrvery own outwards by "gravity assist" in the time of cshed encounters (Oort cloud); Some dust stays in a dust disk in the plane of the solar system; we check out it from the zodiacal light it scatters.. How huge is it? Pluto"s orlittle at 40 AU, Kuiper Belt in between 30 and 100 AU or so, the Oort Cloud extends out to 50,000-100,000; The nearemainder star is at around 300,000. What Evidence Do We Have? Earth and also Moon rocks: They deserve to be dated using their radioactive elements; The earliest ones are about 4.5 billion years old. Meteorites: The earliest objects in our solar mechanism are 4.57-Gyr old, mm-sized grains uncovered in some meteorites; Some also provide us evidence that a star exploded in our area approximately the time the solar mechanism created, and also the Sun might have been component of a cluster. Exploration and experiments: Spacecraft have actually been sent out to observe asteroids made of "primitive rock" (favor NEAR, with asteroid Eros, and Hayabusa, to asteroid Itokawa) and also comets (Rosetta), and also collect samples of solar wind (Genesis); Conditions have actually been recreated in a Gap Shuttle flight. Solar neighborhood: Its configuration also mirrors evidence for some sort of past explosion; For instance, we seem to be inside a bubble with walls about 70 light years away; Additional away, we can check out other (proto)planetary systems where the process is happening ideal now.
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More Twists Jovian planets: Probably formed in stages; How could the ice giants Uranus and also Neptune develop in an area so far from the Sun, via extremely little bit material? They more than likely created closer to the Sun and then "migrated", puburned external by Jupiter..., and in the procedure relocated other debris farther out, to what is currently the Kuiper belt. Terrestrial planets: The outer planets might have actually played an important duty in their formation; Was there a fifth terrestrial earth once, beyond Mars? Gamma ray bursts: Are they regarded the development of the solar system?