You are here

Procyon B

January 21, 2018

The star known as Procyon B is a faint cosmic ember. It’s only a bit bigger than Earth — roughly one percent the diameter of the Sun. And it’s quite close to a bright companion star, Procyon A. That makes it almost impossible to see, even through a big telescope.

That would not have been the case when Procyon B was born. It probably was about twice as massive as the Sun — bigger and heavier than Procyon A is today. That would have made it brighter than Procyon A, too.

Because Procyon B was heavier, it evolved faster. More than a billion years ago, it expelled its outer layers into space, leaving only its dead core — a white dwarf.

The two stars were closer together then. So as Procyon B evolved, it probably had an effect on its companion. As its core died, for example, Procyon B expelled more than two-thirds of its mass; some of that material fell onto its companion.

The extra gas made Procyon A heavier, so it probably accelerated the star’s evolution. As a result, “A” will live a shorter life than it would have otherwise. In fact, it’s already starting to change. In another hundred million years or so, it, too, will shed its outer layers, leaving only its dead core. So the system we know as Procyon will consist of two white dwarfs, shining meekly through the cosmic night.

For now, look for Procyon low in the east as night falls. It rises a little earlier than Sirius, the brightest star in the night sky, which is lower in the southeast.


Script by Damond Benningfield

Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.