Alvin Clark discovers dwarf companion of Sirius

January 31, 1862 Telescope maker Alvin Clark discovers dwarf companion of Sirius.
The first white dwarf to be discovered was found because it is a companion star to Sirius, a bright star in the constellation Canis Major. In 1844, astronomer Friedrich Bessel noticed that Sirius had a slight back and forth motion, as if it was orbiting an unseen object. In 1863, the optician and telescope maker Alvan Clark spotted this mysterious object. This star was later determined to be a white dwarf. This pair are now referred to as Sirius A and B, B, being the white dwarf. The orbital period of this system is about 50 years.

Since white dwarfs are very small and thus very hard to detect, binary systems are a helpful way to locate them. As with the Sirius system, if a star seems to have some sort of unexplained motion, we may find that the single star is really a multiple system. Upon close inspection we may find that it has a white dwarf companion.