A faint star of 8th magnitude in a binary system with → Sirius.
Called also Sirius B, it is a → white dwarf with a mass comparable to
that of the Sun, but with a diameter smaller than that of the Earth. The mean distance
between the stars is about 20 A.U. (angular separation 4.6 seconds of arc), and their period of
revolution about 50 years. This star was discovered in 1844 by Friedrich Bessel,
who noticed that Sirius had a slight wobbling motion, as if it was orbiting an unseen object.
In 1863, the optician and telescope maker Alvan Clark spotted the companion.
The star was later determined to be a → white dwarf.
See also: → companion; → Sirius.
