You are here

Bright Paw

February 13, 2015

Sirius, the leading light of Canis Major, the big dog, scoots low across the south on winter nights. It’s also the brightest star in the entire night sky, in large part because it’s a close neighbor — less than nine light-years away.

Several of the other stars that outline the dog are far more impressive. In fact, a star that’s close to the right of Sirius is probably more than a thousand times brighter. But its light is dimmed by its distance — about 500 light-years.

Mirzam shines so brightly because it’s much bigger and hotter than the Sun. The greater size means there’s a lot more surface to radiate energy into space. And the hotter temperature means that a given surface area on the star radiates more energy than the same size patch on the Sun.

The star is also much heavier than the Sun — perhaps 15 times the Sun’s mass — so it “burns” through the nuclear fuel in its core in a hurry. So even though Mirzam is less than one percent of the age of the Sun, it’s already nearing the end of its life. Sometime soon — in the next few million years — it’ll blast itself apart as a supernova. For a few days, it will outshine the combined light of most of the galaxy’s other stars — and make Sirius look like a sickly firefly by comparison.

For now, look for Mirzam to the right of Sirius, where it represents one of the dog’s paws. It’s a star that’s following a famous bit of advice: Live fast, die young, and leave a good-looking corpse.


Script by Damond Benningfield, Copyright 2014

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.