When it comes to understanding an exploding star, one number trumps all: distance. If astronomers don’t know the distance to a dying star, they can’t be sure how the star is going out.

That may be the case with CK Vulpecula. Normally, it’s too faint to see with the eye alone. But centuries ago, it flared up. It first grew bright enough to see in 1670. Then it grew brighter still in March of 1671 — 350 years ago this month.

The leading idea has been that the flare-up was produced by the collision and merger of two stars. Different models have come up with different types of stars, but the basic idea has stayed the same.

A recent study, though, found that CK Vulpecula may be five times farther than shown by earlier measurements — about 10,000 light-years. If so, then the outburst was about twenty-five times brighter than thought.

A collision between two stars wouldn’t be powerful enough to make the star shine that brightly. Yet the outburst wouldn’t have been bright enough to be the result of a supernova — a titanic explosion that rips a star to bits. So CK Vulpecula may be an in-betweener — a type of explosion that can’t yet be explained.

CK Vulpecula is far too faint to see without a telescope. Yet its location is easy to pick out. It’s in Vulpecula, the fox. It stands near the middle of the bright Summer Triangle, which is high in the eastern sky at first light on March mornings.

Script by Damond Benningfield

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