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Sigma Scorpii

The scorpion curves along the southern horizon as darkness falls on these late-summer evenings, with the bright orange star Antares at its heart.

Antares is one of the most impressive stars in the galaxy — a supergiant that’s destined to explode as a supernova. But a fainter star that stands close to its right is pretty impressive, too. Sigma Scorpii consists of four stars, at least one of which also will end its life with a giant bang.

Two of the four stars form a tight pair — their surfaces are separated by about half the distance from Earth to the Sun. They’re so close together that even the biggest telescopes see them as a single point of light. But instruments that break the light into its individual wavelengths measure two stars, not one.

Both stars are much bigger, brighter, and heavier than the Sun. Their details have proved a bit elusive, but the dominant member of the pair appears to be about 18 times as massive as the Sun and about eight times the Sun’s diameter. Its companion is smaller and lighter, but still a stunner.

The heavier star is almost certain to explode as a supernova sometime in the next few million years. The companion is likely to go as well, although it’s closer to the mass limit for a star to become a supernova. Above that limit, it goes boom. Below it, the star sheds its outer layers more gently, leaving its hot, dense core — a dead star known as a white dwarf.

Script by Damond Benningfield

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