Looking Up: On Its Last Dogleg

Mar 18, 2019

Credit constellation photo by unknown author licensed under creative commons; additional 'struggling star' artwork created by A.R. Procell / CC BY-SA-NC

This week on Looking Up we learn about a distant star that sure could use a leg up on finding another supply of hydrogen for its core.

If you have been thinking that these Looking Up segments are increasingly going to the dogs, I must agree, at least about today, because I want to tell you about a neat star in the constellation Canis Major, or the big dog, that follows Orion the Hunter across the Colorado night sky right now. The special star is Mirzam, the right front leg of the big dog, below and to the right of the brightest star in the sky, Sirius.

As it turns out, Mirzam is actually far brighter that Sirius, but because it is 60 times farther away, it seems less bright to us here on Earth. But if Mirzam was as close to us as Sirius, Mirzam would be the third brightest thing in the sky, after the Sun and the Moon. In fact, Mirzam would be 15 times brighter than Venus! It’s 35,000 times brighter than our Sun.

How does it burn so bright? Well, Mirzam is a bright blue super-giant star. It’s done, or is nearly done, fusing all the available hydrogen, and it’s well on its way to its ultimate fate, an explosion as a supernova. After that, the big dog will develop quite a limp!

If you’d like to take a closer look at Mirzam, or any of the other wonderful and amazing things in the sky, please visit csastro.org for a link to information on our monthly meetings and our free public star parties.