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Answer: A low or medium mass star, with mass less than about 8 times the mass of our Sun, ends its life as a white dwarf: a star remnant about the size of Earth that is one of the densest forms of matter, surpassed only by neutron stars and black holes.

How a star becomes one

Medium mass stars, like our Sun, live by fusing the hydrogen within their cores into helium. That fusion creates an outward pressure that balances gravity. In another 5 billion years, the Sun will have used up all the hydrogen in its core. When the Sun runs out of hydrogen to fuse, the balance tips in the favor of gravity, and the star starts to collapse.

How dense

A typical white dwarf is about as massive as the Sun (S1) or half as massive as the Sun (S2), yet only slightly bigger than Earth. That means a white dwarf is 200,000 times as dense as Earth.

Odd properties

• The more massive a white dwarf is, the smaller it is.
• There is a limit on its mass: Subrahmanyan Chandrasekhar found it to be 1.4 times the mass of the Sun, known as the "Chandrasekhar limit."
• With a surface gravity of 100,000 times that of Earth, heavier atoms in its atmosphere sink and lighter ones remain at the surface.
• Scientists hypothesize a crust 50 km thick below the atmosphere of many white dwarfs, with a crystalline lattice of carbon and oxygen atoms at its bottom.

Claims

• id: C1 claim: The balance between pressure and gravity in a star is very delicate. source: S1 evidence: "The balance between pressure and gravity is very delicate."
• id: C2 claim: The more massive a white dwarf is, the smaller it is. source: S2 evidence: "For example, the more massive a white dwarf is, the smaller it is."
• id: C3 claim: Chandrasekhar found the white dwarf mass limit to be 1.4 solar masses. source: S2 evidence: "Subrahmanyan Chandrasekhar discovered this limit to be 1.4 times the mass of the Sun."

Sources

• [S1] Imagine the Universe!. NASA. https://imagine.gsfc.nasa.gov/science/objects/dwarfs1.html . License: US government work, public domain. Accessed 2026-11-04.
• [S2] Imagine the Universe!. NASA. https://imagine.gsfc.nasa.gov/science/objects/dwarfs2.html . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_met1m097,
  author = {{iinventedlight}},
  title = {{White dwarfs: what happens to stars like the Sun}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/white-dwarfs/},
  note = {Permanent ID iil:note:met1m097. License: CC-BY-4.0.},
}

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