A White Dwarf So Massive That It Might Collapse

[Judi Lynn]

June 30, 2021 Caltech

Astronomers have discovered the smallest and most massive white dwarf ever seen. The smoldering cinder, which formed when two less massive white dwarfs merged, is about 4,300 kilometers across, or somewhat larger than Earth’s moon.

Though the white dwarf is small, it is heavy, “packing a mass greater than that of our sun into a body about the size of our moon,” says Ilaria Caiazzo, the Sherman Fairchild Postdoctoral Scholar Research Associate in Theoretical Astrophysics at Caltech and lead author of the new study appearing in the July 1 issue of the journal Nature. “It may seem counterintuitive, but smaller white dwarfs happen to be more massive. This is due to the fact that white dwarfs lack the nuclear burning that keep up normal stars against their own self gravity, and their size is instead regulated by quantum mechanics.”

The discovery was made by the Zwicky Transient Facility, or ZTF, which operates at Caltech’s Palomar Observatory; a host of other telescopes helped characterize the dead star, including: the 200-inch Hale Telescope at Palomar, the W. M. Keck Observatory’s Keck I telescope, the European Gaia space observatory, the University of Hawaii’s Pan-STARRS (Panoramic Survey Telescope and Rapid Response System), and NASA’s Neil Gehrels Swift Observatory (which was renamed after Gehrels, a Caltech alumnus, who passed away in 2017). ZTF is funded by the National Science Foundation (NSF) and other collaborators.

White dwarfs are the collapsed remnants of stars that were once about eight times the mass of our sun or lighter. Our sun, for example, after it first puffs up into a red giant in about 5 billion years, will ultimately slough off its outer layers and shrink down into a compact white dwarf. About 97 percent of all stars become white dwarfs.

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[Delphinus]

1. Thank you

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[BlueWavePsych]

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