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October 30, 2017

In Greek mythology, Perseus was a hero — he rescued the princess Andromeda from a nasty sea monster. And the brightest star of the constellation that depicts Perseus befits a hero: It’s big, heavy, and bright.

Mirfak is far more impressive than the Sun: seven or eight times heavier, about 60 times wider, and about 5,000 times brighter. That makes it easy to see even though it’s more than 500 light-years away.

Yet there’s more to Mirfak than meets the eye — perhaps including a companion star.

Mirfak produces a lot of X-rays. That’s a bit of a surprise for a star of its temperature and stage of life. That could mean that Mirfak is an oddball — that some unknown mechanism is causing it to produce the X-rays. But it also could mean that it has an unseen companion — a smaller star with a hot outer atmosphere, like the Sun’s corona.

Searches for such a star have turned up empty — so far. But the system is so far away, and Mirfak itself is so bright, that a companion easily could be hidden in Mirfak’s glare. If such a star exists, it would only add to the impressiveness of the hero’s leading light.

And that light is in the northeast as darkness falls, above the brighter star Capella. Mirfak is an easy target even from light-polluted cities. Most of the constellation’s other stars stream away to its right and lower right. That includes the hero’s second-brightest star — the “demon” star. We’ll have more about that tomorrow.


Script by Damond Benningfield

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