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Moon and Aldebaran

February 15, 2016

The Moon glides up on the bright eye of the bull tonight. Aldebaran is close to the left of the Moon as night falls. Later, the gap between them will close, as the Moon moves toward the bright star. And as seen from California and Hawaii, the Moon will catch Aldebaran and pass in front of it, blocking it from view in the wee hours of the morning.

It’s hard to notice through the glare of the Moon, but Aldebaran shines bright orange. The color is an indication of its surface temperature, which is much cooler than the Sun. Because of that, Aldebaran is designated as class K.

Astronomers use seven letters to classify true stars — O, B, A, F, G, K, and M.

O stars are the hottest. They blaze tens of thousands of degrees hotter than the Sun, so they shine blue-white. They’re also among the biggest, heaviest, and brightest of all stars.

At the other end are the M stars, which are the coolest. They look orange or red. Almost all M stars are so small and faint that they’re invisible to the unaided eye. But some are bloated and brilliant — stars that have swelled to giant proportions at the ends of their lives.

The Sun is class G. It’s bigger and heavier than most stars, but nowhere near the monsters at the top of the classification scheme.

As it nears the end of its life, though, the Sun will look much like Aldebaran does today — a bloated orange giant, designated as either K or M — at the red end of the stellar classification system.

Script by Damond Benningfield, Copyright 2015

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