Moon and Companions

The Moon has a couple of bright companions tonight and tomorrow night. The brighter one is the giant planet Saturn, which looks like a bright star close to the upper left of the Moon as darkness falls this evening. The other is the star Fomalhaut. It’s farther to the lower left of the Moon, and it’s only about half as bright as Saturn. But it’s the only noteworthy star in that region of the sky, so it’s hard to miss.

For more than a decade, it looked like Fomalhaut might have a giant planet of its own. Hubble Space Telescope took pictures of it — a tiny dot of light far from the star. And astronomers even gave it a formal name: Dagon.

But a few years ago, the dot of light spread out, then faded from sight. That means the object probably was a giant cloud of dust. When Hubble first saw it, the cloud had just formed — probably debris from a collision between two asteroids. Over the years, the dust spread out. Eventually it became so thinly spread that we could no longer see it.

Even so, it’s possible that Fomalhaut could have one or more planets. A disk of gas and dust encircles the star. Voids within the disk could have been swept clean by orbiting planets. In addition, the gravity of planets could account for some “clumpy” regions in the disk. So far, though, these are only suggestions that Fomalhaut has planets. The worlds themselves — if they exist at all — still await discovery.
 

Script by Damond Benningfield