Third Dog

A huge star in Canis Major, the big dog, is getting ready to flood the interstellar market with huge supplies of chemical elements — everything from carbon and oxygen to silicon and iron. In fact, it’ll dump enough material to make several stars as massive as the Sun.

Wezen is Canis Major’s third-brightest star. It rises directly below the top dog, Sirius — the brightest star in the night sky. They’re in good view in the southeast by 8 or 8:30.

Wezen is a supergiant. It’s so large that if it took the Sun’s place in our own solar system, it would extend all the way out to Earth. It’s also more than 15 times as massive as the Sun. That extra weight squeezes the star’s core, heating it and revving up its nuclear “engine.”

And that’s what makes Wezen such a busy chemical factory. Stars fuse together lightweight elements in their cores to make heavier ones. They do so in stages. In the first, they fuse hydrogen to make helium. Next, they fuse the helium to make carbon, oxygen, and nitrogen. Stars like the Sun stop there. But heavy stars make even heavier elements — all the way up to iron.

When the core is converted to iron, it takes more energy to make heavier elements than the star can produce. So fusion stops and the core collapses. The outer layers then explode as a supernova. That expels many of the elements created inside the star into space — which is just what will happen with Wezen in a few million years.

Script by Damond Benningfield