What is Planetary formation: Definition and 11 Discussions

The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting the Sun. The theory was developed by Immanuel Kant and published in his Universal Natural History and Theory of the Heavens (1755) and then modified in 1796 by Pierre Laplace. Originally applied to the Solar System, the process of planetary system formation is now thought to be at work throughout the universe. The widely accepted modern variant of the nebular theory is the solar nebular disk model (SNDM) or solar nebular model. It offered explanations for a variety of properties of the Solar System, including the nearly circular and coplanar orbits of the planets, and their motion in the same direction as the Sun's rotation. Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded.
According to the nebular theory, stars form in massive and dense clouds of molecular hydrogen—giant molecular clouds (GMC). These clouds are gravitationally unstable, and matter coalesces within them to smaller denser clumps, which then rotate, collapse, and form stars. Star formation is a complex process, which always produces a gaseous protoplanetary disk (proplyd) around the young star. This may give birth to planets in certain circumstances, which are not well known. Thus the formation of planetary systems is thought to be a natural result of star formation. A Sun-like star usually takes approximately 1 million years to form, with the protoplanetary disk evolving into a planetary system over the next 10–100 million years.The protoplanetary disk is an accretion disk that feeds the central star. Initially very hot, the disk later cools in what is known as the T Tauri star stage; here, formation of small dust grains made of rocks and ice is possible. The grains eventually may coagulate into kilometer-sized planetesimals. If the disk is massive enough, the runaway accretions begin, resulting in the rapid—100,000 to 300,000 years—formation of Moon- to Mars-sized planetary embryos. Near the star, the planetary embryos go through a stage of violent mergers, producing a few terrestrial planets. The last stage takes approximately 100 million to a billion years.The formation of giant planets is a more complicated process. It is thought to occur beyond the frost line, where planetary embryos mainly are made of various types of ice. As a result, they are several times more massive than in the inner part of the protoplanetary disk. What follows after the embryo formation is not completely clear. Some embryos appear to continue to grow and eventually reach 5–10 Earth masses—the threshold value, which is necessary to begin accretion of the hydrogen–helium gas from the disk. The accumulation of gas by the core is initially a slow process, which continues for several million years, but after the forming protoplanet reaches about 30 Earth masses (M⊕) it accelerates and proceeds in a runaway manner. Jupiter- and Saturn-like planets are thought to accumulate the bulk of their mass during only 10,000 years. The accretion stops when the gas is exhausted. The formed planets can migrate over long distances during or after their formation. Ice giants such as Uranus and Neptune are thought to be failed cores, which formed too late when the disk had almost disappeared.

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    A What is a Bern model in planetary population synthesis?

    Hello. I'm writing my Master Thesis about planetary population synthesis and one of the chapters is about the different models. I found that most of them are Bern models with some modifications. What is a Bern model in planetary population synthesis and what references can I read about it...
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    I Planetary Formation: Could Collisions Explain Our Solar System?

    I'm very much an amateur with a keen interest in space/the universe and it occurred to me the other day that our solar system could have been formed in exactly the same way that it is hypothesised that the Moon/Earth system formed through the (proposed) collision of Theia and the proto-Earth...
  3. C

    Lagrangian mechanics and planetary formation

    I am disappointed by my graduate-level classical mechanics course, and especially the treatment of Lagrangian/Hamiltonian mechanics. Now, I scanned my notes and some crazy idea popped into my head, further fueling my discontent towards this course, because all the problems covered in class were...
  4. B

    Mass planetary formation calculation?

    Homework Statement Compute the mass of volatile material (specifically just H and He) not accreted by the Earth. Assume the mass accreted by the Earth is 7e23 kg. How does the mass of the missing volatiles compare with the actual mass of the Earth? Use the following table: Principal...
  5. I

    Planetary Formation and Rossby Waves

    I've looked at a number of articles and the idea that Rossby waves play a key role in planetary formation seems to be in style. I have a few questions. What are the necessary and sufficient conditions for formation of Rossby waves in a rotating self-contained system? I'd guess it happens...
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    Planetary Formation Based on Matter Condensation and Accretion

    The understanding of the origins of our planet (as well as the other planets in the Universe) has always remained a question to astronomers. Inherently, the application of Newton’s known concepts of gravity has granted us the ability to make educated assumptions concerning planetary formation...
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    Planetary formation and effects of gravity

    I was curious as to how planetary type spherical bodies form. Specifically, I was curious as to how the gravity affects the nebulous particles moving within themselves just prior to a solid planetary body forming. Is it not true that gravity is essentially zero in the center of a planetary...
  8. wolram

    Favoured theory for planetary formation

    Can someone tell me which is the favoured theory for planetary formation, core accretion or Gravitational instabilities, and if these are the only valid theories?
  9. wolram

    Prevention of planetary formation

    http://www.spaceref.com/news/viewpr.html?pid=13330 To their surprise, the researchers found that in specific cases, the computer calculations suggested that the sphere would change shape dramatically. Frey said these special circumstances, called singularities, might ultimately reveal...
  10. M

    A question of Planetary formation.

    My question pertains to atmosphere. Forgive me if it sounds stupid, or obvious, but I just don't know how atmospheres come about. I understand how planetoids and planets are formed, but when/how does it get an atmosphere? Any help would be appreciated.
  11. D

    Early planetary formation thought

    Greetings ! Some less popular theories, at this time, suggest that planets formed or at least began to form before the Sun had formed. I'm not sure that I agree with that, but it's worth remembering as another counter example to the idea I just thought about. Anyway, the idea I just...