We know when a star runs out of its main hydrogen fuel, thermonuclear fusion ceases. Gravity stars pulling it and there is no force anymore to counter the gravity so the star crashes or dies at a point. But what if the star at the end moment of its life suddenly found another star of just the perfect size and distance and start orbiting it and somehow managed to maintain equilibrium by being pulled by that 'another star'. What would the dying star then look like with all it's hydrogen and gases ran out but still maintaining equilibrium?
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$\begingroup$ Orbiting another body will only add tidal forces to the equation. It will not counteract the force of gravity all over the star and prevent collapse. $\endgroup$– Laff70Commented Nov 18, 2022 at 15:55
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$\begingroup$ Does that mean earth's gravity is also not effected by orbiting around the sun? Like not lessened nor increases somewhat? $\endgroup$– Enix LetzenCommented Nov 18, 2022 at 15:59
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$\begingroup$ @EnixLetzen Search terms: “spring tides” and “neap tides.” $\endgroup$– rob ♦Commented Nov 18, 2022 at 16:11
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$\begingroup$ Re We know when a star runs out of its main hydrogen fuel, thermonuclear fusion ceases. We do not know that. Google "red clump", for example. Stars larger than half a solar mass or so start fusing helium when the hydrogen in the core runs out. $\endgroup$– David HammenCommented Nov 18, 2022 at 16:53
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A low-mass star which exhausts its hydrogen fuel will contract, either until its core becomes hot enough to start helium burning or some heavier fusion process, or until the core is supported by electron degeneracy pressure. Various intermittent processes will cause the non-degenerate envelope to be expelled, until only the degenerate core remains. This is called a “white dwarf.” Your favorite book on stellar evolution discusses lots of details.
A gravitationally bound system of hydrogen and helium which is not hot enough to incandesce can support chemical reactions among its trace elements. For visual appearance, we have several examples in our solar system: the “gas giant” planets.
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$\begingroup$ The question appears to be about binaries, so perhaps en.wikipedia.org/wiki/Cataclysmic_variable_star and en.wikipedia.org/wiki/X-ray_binary are relevant. $\endgroup$ Commented Nov 18, 2022 at 16:10
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$\begingroup$ Oh my god, thank you! I understood a lot about my question studying this binary and X ray binaries, there were just it! $\endgroup$ Commented Nov 18, 2022 at 17:13