Sirius B

Sirius B is the faithful companion of Sirius, the brightest star in the night sky. But Sirius B itself is tiny – about the size of Earth! Yet it weighs as much as our entire Sun. Imagine squishing the Sun down to the size of a planet – a sugar cube of that stuff would be heavier than an elephant! Sirius B is over 25,000 degrees hot and glows bluish-white, but because it's so small, you can only see it with powerful telescopes. It was the first white dwarf humans ever discovered – over 160 years ago!