The stars of the Sirius binary star system are about the same age, around 250 million years old. But because Sirius B (to the right in this artist’s impression) was originally more massive, it’s now further along in its stellar evolution. Credit: NASA, ESA and G. Bacon (STScI)
Sirius is a blue giant, which burns through its fuel quickly and lives only a relatively short period of time. Yet it has a white dwarf companion (Sirius B) and white dwarfs are the end result of stars like our Sun, which live for billions of years. How can a young blue giant have a companion star that’s billions of years older?
John Gould
Moab, Utah
This is a great question. It hinges on the fact that while we often say that white dwarfs are the remnants of Sun-like stars, the term Sun-like in this case is admittedly a bit of an oversimplification.
