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Moon and Aldebaran

July 1, 2016

Most of the skywatching action has been concentrated in the evening sky for the last few months. But there’s a nice bit of business in the morning sky tomorrow: the crescent Moon snuggles close to the eye of the bull. There’s not much time to look, though — the dawn twilight will overpower them in a hurry.

The eye of Taurus, the bull, is Aldebaran, a star that shows us what the Sun will look like in a few billion years: big, fluffy, bright, and orange.

All of those traits are part of the natural aging process for stars like Aldebaran and the Sun. Such a star spends most of its life steadily “fusing” the nuclei of hydrogen atoms in its core to make helium — just what the Sun is doing right now. When that process is done, the core shrinks and gets hotter. That causes the star’s outer layers to puff up.

That makes the star get much bigger. But since it doesn’t add any material, it gets less dense, so its outer layers get fluffy. The star eventually swells to many times its original size. With that much surface area, it gets brighter. And the puffed-up gas gets cooler, which makes the star glow orange or red.

And that’s where Aldebaran is right now: big, fluffy, bright, and orange — a picture of what the Sun will look like in the distant future.

Look for Aldebaran close to the upper right of the Moon, quite low in the eastern sky at first light tomorrow. They’re still low in the sky as twilight begins to overpower them.

Script by Damond Benningfield

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