When we look into the sky, we see one big, blinding star — the Sun. All the other stars are mere pinpoints of light; the brightest star in the night sky looks less than a hundred-billionth as bright as the Sun.

But the residents of many other star systems would have two or more bright stars to look at it. That’s because most of the stars in the galaxy are members of systems with two stars, three stars, or even more.

An example is Dubhe, which marks the lip of the Big Dipper’s bowl. The dipper is high in the northwest at nightfall, with Dubhe at the bottom, as though pouring the dipper’s contents onto the ground.

Dubhe actually consists of two pairs of stars.

The brighter pair is quite impressive. One of its members is a giant. The star is nearing the end of its life, so changes in its core have caused its outer layers to puff up. The star is almost 20 times wider than the Sun, and hundreds of times brighter. Its bloated surface is fairly cool, so it glows orange.

The star’s companion is no slouch, either. It’s still in the prime of life, just as the Sun is. But it’s more massive than the Sun, so it shines brighter. And its surface is much hotter than the Sun’s, so it shines pure white.

The stars are a couple of billion miles apart — more than 20 times the distance from Earth to the Sun. Even so, if a planet orbits either star, both stars would appear blindingly bright — two “suns” for the price of one.
 

Script by Damond Benningfield

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