Some “monstrous” stars decorate the Halloween sky this evening. They’re in Perseus, which is low in the northeast at nightfall but passes directly overhead in the wee hours of the morning. The constellation is marked by a couple of ribbons of moderately bright stars.

In mythology, Perseus rescued the princess Andromeda from a nasty sea monster. In one version of the story, he turned the monster to stone by showing him the head of Medusa, one of the Gorgons – monsters in their own right.

Four stars in the constellation are tied to that story. Together, they’re known as the Gorgons. And the most impressive of the four is quite the monster.

Gorgonea Tertia – the third Gorgon – is entering the final stage of its life. It converted the original hydrogen fuel in its core to helium, then converted the helium to carbon and oxygen. The core isn’t hot enough to continue the process, though, so it’s no longer generating energy. But it’s hot enough to push on the layers of gas around it, making the star puff up to enormous proportions.

Today, Gorgonea Tertia is roughly 150 times wider than the Sun. In the near future – on the astronomical timescale – the star will get even bigger and brighter. After that, it will eject its outer layers, creating a colorful bubble. But the bubble will quickly expand so much that it’ll fade from view. That will leave only the star’s hot but dead core – a meek end for a monstrous star.

Script by Damond Benningfield