The first member of a new important class of astrophysical objects, white dwarf
Sirius B, was
discovered by chance. On January 31, 1862 American telescope maker Alvan Clark first saw Sirius B while observing star Sirius for testing the 47 cm lens he was making for the Dearborn Observatory refracting telescope, then the largest in the world. Clarke observed
Sirius, the brightest star in the sky, because he needed a bright, point-like light source for optical testing. A
white dwarf is
a small, dense star originating from the final evolutionary state of stars like the Sun.