Sirius B

Sirius B is a white dwarf star, the dense remnant of a once-active star that exhausted its fuel. Located about 8.6 light-years from Earth, it orbits its brighter companion, Sirius A, in a system known as the Sirius star system. White dwarfs are incredibly dense; a teaspoon of Sirius B's material would weigh a few tons on Earth. Despite its small size—about Earth-sized—it contains half the mass of the Sun, showcasing the intense compression of its core. Sirius B provides valuable insights into stellar evolution, illustrating what stars become after they have finished nuclear fusion.