Moon and the Scorpion

For most stars, life seems to happen in slow motion — it takes a long time for them to change. One exception appears near the Moon tonight. Over the last 25 years it’s gotten a lot brighter, and it’s created a “pancake” of gas and dust around itself.

Delta Scorpii is close to the lower right of the Moon as night falls. It’s the middle star in the “head” of the scorpion. The scorpion’s brightest star, Antares, is farther to the lower left of the Moon.

Delta Scorpii is about 450 light-years away. It consists of two stars. One of them is about 14 times the mass of the Sun. The other is about two-thirds as heavy.

The stars orbit each other once every 11 years. The orbit is stretched out, so most of the time the stars are a long way apart. At their closest, though, they’re closer than Earth is to the Sun.

By the time of a close approach in 2000, the bigger star had surrounded itself with the pancake — something that hadn’t been seen before. The star is big and puffy, and it spins in a hurry. That appears to be throwing gas from its equator, forming the disk.

As the smaller star moves inward, it may stir and heat the disk, making the system shine brighter. In fact, it got roughly twice as bright early in this century.

The stars made their last close approach 10 years ago this month, so they’ll get close again next year. Astronomers will be watching to learn more about this rapidly changing system.
 

Script by Damond Benningfield