11,268 kmdiameter
Details
Sirius B is the white dwarf companion of Sirius A, the brightest star in the night sky. Hubble measurements show it packs about the Sun’s mass into a body smaller than Earth, with gravity so strong that a person would weigh tens of millions of pounds on its surface.
Sirius B is the exposed core left after a star exhausted its nuclear fuel and shed its outer layers. Hubble measurements put its mass at about 98 percent of the Sun's, compressed into a diameter smaller than Earth's. Electron degeneracy pressure, a quantum effect that resists packing electrons into the same states, supports the remnant against further collapse.
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Measurements and descriptive context are compiled by the Scale of Space team from the references below. If you find an error, please let us know.
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