Sirius A vs Sirius B

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.

Object class

White dwarf star

Mass

~1.02 solar masses

Host

Sirius system

Estimated age

~228 million years

Composition

Electron-degenerate carbon-oxygen matter

Temperature

~25,000 K surface

Sirius A is the brightest star in Earth’s night sky and the luminous primary of the Sirius binary. The same system also contains Sirius B, a white dwarf.

Object class

A-type main-sequence star

Mass

~2 solar masses

Host

Sirius system

Estimated age

~240 million years

Composition

Hydrogen and helium

Temperature

~9,900 K surface