The night sky is a time machine. All of the stars are light-years away, so we see them as they looked years ago. But one star also shows us the future. It gives us a glimpse of what the Sun will look like in perhaps a billion years or more.

Chara is the second-brightest member of Canes Venatici, the hunting dogs. The constellation is in the east-northeast at nightfall. Chara is above its brightest star, Cor Caroli.

Chara is a solar analog — a star that’s almost identical to the Sun. It’s a couple of percent more massive than the Sun, and a little bit bigger and brighter. But it’s almost the same color and temperature as the Sun. So it looks a lot like the Sun would for anyone at Chara looking our way.

The small differences in size and brightness are mainly due to the star’s extra weight. Heavier stars burn their nuclear fuel more quickly than lighter stars, so they’re bigger and brighter.

But some of the difference is a result of Chara’s age. Most estimates say it’s at least several hundred million years older than the Sun, and perhaps as much as a billion and a half. As a star ages, the nuclear reactor in its core must work harder to produce energy. That makes the core hotter, which causes the star’s outer layers to puff up.

And that’s what’s ahead for the Sun. In a billion years, in fact, it may be so big and bright that it will have boiled away Earth’s oceans and atmosphere — leaving nothing but a cosmic cinder.

Script by Damond Benningfield


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