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6

The slowest reaction rate in the pp chain determines how quickly hydrogen can "burn" in the core of a sun-like star. That rate-determining step is actually the fusion of two protons to form deuterium via the diproton and a weak interaction decay. The fusion of lithium, whereby it fuses with a proton and then splits into two Helium nuclei is actually part of ...


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I think that there isn't a strict answer to this question. However, I believe the answer is that there's a difference between the core of a hydrogen-burning star and the core of a protostar or star-forming, gas cloud. For a hydrogen-burning star, the core, as you say, is the region of the star where fusion is taking place. This is surrounded by the ...


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The test to see whether degeneracy pressure is going to be significant is to compare $kT$ with the Fermi energy $E_F$ The Fermi energy is the energy level up to which all energy states would be occupied in a completely degenerate fermion gas. It is given by (for non-relativistic conditions) $$ E_F = \frac{h^2}{2m}\left(\frac{3}{8\pi}\right)^{2/3} n^{2/3},$$...


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Regarding the title: Yes. Does this mean that the star started off as a planet? Yes, a star could technically start out as a planet, if it accreted enough mass. However, this is extremely unlikely, since the planet would need to be 80x the mass of Jupiter for it to undergo nucleosynthesis. Stars require hydrogen fusion and earth has little H. Could ...


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The lines show as either peaks above the black body emission (for emission lines) or troughs below the black body emission (for absorption lines). Though stars more often have absorption lines and nebulae emission.


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Think of when the planet is at the "side" - there's a little bit of light from the planet (ie, reflecting off the planet) shining towards us. Could it be due to that little bit of light - when the planet is behind the star, it no longer reflects towards us? Maybe that's the effect you have in mind?


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Globular clusters formed whilst the gas of the proto Milky Way was still approximately spherically distributed. The gas forms a dissipative system that loses energy and collapses (within the first billion years) to a disk whilst conserving angular momentum. Formed stars and clusters are essentially collisionless so the halo stars continue to have a ...


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You are right; when referring to stars such as the Sun, the core is usually defined as the volume in the centre where fusion is taking place. In the case of larger stars with fusion occurring in multiple layers, the core is still taken to be the area in the middle where nuclear fusion is producing the heaviest elements. With protostars or pre-main-sequence ...


2

There are a variety of scenarios in which a star can emit gases, although that's probably not the best way to think about it. A better way to visualize it is in terms of mass loss rather than gas emission. Inevitably, most or all of a stars mass must eventually go "back to the galaxy in which they are in." https://en.wikipedia.org/wiki/Stellar_mass_loss In ...


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The initial stars were made of hydrogen and helium. These enriched the interstellar medium (ISM) with some chemical elements right across the periodic table, when massive primordial stars ended their lives as supernovae. Subsequent generations of stars continue to enrich the ISM, if their lives are short enough. So the general gist of what you suggest is ...


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A star does not start off as a planet; you have a large cloud of gas that is collapsing in on itself due to gravity. The majority of the gas goes towards creating the star (more than 99% in the case of our Solar System). However, gravitational collapses can occur several places in the gas cloud, and some of the gas will contribute towards the collapse of far ...


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Just to add, while I think Rob Jeffries answer covers it. Now is it expected that in future more stars will be made of more heavy elements or are there causes/laws which prohibit stars forming of e.g. stars made of elements without hydrogen. While this is unlikely to happen because Hydrogen will stick around as the most abundant element for a very ...


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NO The differences between a brown dwarf and a low mass star are based upon their mass. A brown dwarf does not have central temperatures and pressures to create energy using hydrogen fusion. The mass is too low to create these conditions. A star by definition is an object where energy is created using hydrogen fusion. This happens when the core temperature/...


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Yes If a brown dwarf count as a star in this case, the solution is as easy as a smaller brown dwarf orbiting a larger one. If not, it is still possible if you have two brown dwarfs orbiting close to each other, both just too small to be red dwarfs, together out-massing an orbiting red dwarf, just large enough to be counted as a star. While I have no ...



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