Sirius B 
On the night of January 31st, 1862, Alvan Clark and his son, Alvan Graham Clark, were testing a lens for a new telescope. Clark and his sons were the world’s leading telescope makers. In fact, many of their creations are still in use today, more than a century after the last of them was produced.
The new lens was one of the world’s largest — 18-and-a-half inches in diameter. To test it, the Clarks turned it toward Sirius, the brightest star in the night sky. Within moments, the younger Clark discovered that the star had a companion — a dot so faint and so close to Sirius itself that it had never been seen through the star’s glare.
The companion had been predicted, though, by German astronomer Friedrich Bessel.
Beginning in 1834, Bessel spent a decade measuring the motions of Sirius and other stars across the sky. He found that Sirius seemed to have a “wiggle” in its path. From that, he deduced that the bright star had an unseen companion, and that the two bodies orbited each other once every 50 years. The Clarks confirmed Bessel’s deductions, bringing accolades for both Bessel and themselves.
The companion was named Sirius B, while the bright star became Sirius A. And since Sirius itself is nicknamed the Dog Star because it’s the brightest star of Canis Major, the big dog, Sirius B was nicknamed “the Pup.”
Astronomers quickly found that it was a strange puppy, though — a type of star they couldn’t explain. More about that tomorrow.
Script by Damond Benningfield, Copyright 2011