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Doomed Stars

Aquila, the eagle, spreads its wings across the evening sky as we head into summer. Right now, it’s low in the east a couple of hours after sunset. Its brightest star, Altair, is at the bottom right point of the wide-spread Summer Triangle. Altair represents the eagle’s breast, with its wings above and below.

A pair of stars at one of the wingtips faces a spectacular future. The two stars will ram together, then explode as a supernova — in about 700 million years.

The system is known as Henize 2-428. It consists of two white dwarfs — the dead cores of once-normal stars like the Sun. They’re only a few hundred thousand miles apart — so close that they orbit each other once every four hours. As they orbit, though, they radiate gravitational waves — a process that causes them to spiral closer and closer.

Each of the stars is a bit less massive than the Sun. So when they merge, they’ll be almost twice as massive as the Sun. And for a white dwarf, that’s a bad thing. With that much mass, the white dwarf can’t hold itself together. It undergoes a runaway nuclear reaction that blows the star to bits.

Such an explosion is known as a supernova, and it’s extremely bright. For a few hours, the explosion may shine as brightly as the rest of the stars in the galaxy combined. The exploded stars will leave behind an expanding cloud of debris that will glow for thousands of years — the last hurrah of a pair of doomed stars.

Script by Damond Benningfield


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