"Van Maanen is a dying white dwarf that’s two-thirds the mass of the Sun and just 1% of its size. The helium atmosphere has a puzzling supply of heavy elements—iron, magnesium, and calcium. They might be the dust of a planet crushed by the superdense star’s gravity."
White dwarfs take billions of years to cool, a testament to the immense amount of energy in their youth. The coolest ones on record are about 11 or 12 billion years old. They offer a window into the early universe, which is 13.8 billion years old.
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Black Dwarf?
What happens after the last of a white dwarf’s energy radiates away? It becomes a black dwarf, emitting zero light. Or rather, it will become one—in the future. This stone-cold death takes longer than the universe is old, so no black dwarfs exist yet—as far as we know.
Coolest White Dwarfs
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Quantum Limit
The Chandrasekhar limit is the most mass a stable white dwarf can have—1.4 solar masses. Above that, quantum physics dictates that outward pressure can’t resist gravity, so the star collapses. If it gains mass from a binary star, it explodes as a type Ia supernova.
Van Maanen's Star Rank 3
Stellar Evolution
The life cycle of a star from birth to death is called stellar evolution. (The term refers to stages of aging, not biological evolution.) The oldest star we know is Methuselah, a subgiant calculated to be older than the universe, but with a margin of error.
Van Maanen's Star Rank 6
Trivia[]
A photo of Van Maanen's Star (the top right dark spot)
A screenshot of Van Maanen's Star in SpaceEngine. Circled in red: The Sun
Van Maanen's Star (also known as Van Maanen 2) is a white dwarf of spectral type DZ8.