Moon and Aldebaran

The stars tell us a lot about themselves. A detailed analysis of their light reveals their temperature, composition, and motion. It can also show whether they have companions. But interpreting what the stars are saying isn’t always easy.

Consider Aldebaran, the “eye” of Taurus, the bull. The bright star is close to the Moon in the wee hours of tomorrow morning.

Several faint stars appear quite close to Aldebaran. Most of them aren’t physically related, though — they just happen to line up in the same direction. But one of them could be bound to Aldebaran by their mutual gravity. Despite more than two centuries of observations, though, we’re not sure if that’s the case.

The star is known as Alpha Tauri B. It’s tens of billions of miles from Aldebaran. And that’s part of the problem. The two stars appear to be moving through space in the same direction — an indication that they’re linked. To make sure, though, astronomers need to see the orbital motion of the two stars around each other. But with such a wide gap between them, it would take thousands of years to complete even a single orbit. So there hasn’t been enough time to verify a link between them.

The other problem is that Alpha Tauri B is a red dwarf — a small, faint cosmic ember. Its feeble light is overwhelmed by Aldebaran’s. So it’s hard to plot its position through the glare. That makes it even harder to know if the stars are related, or just passing by each other.

Script by Damond Benningfield