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The Coathanger

June 22, 2019

When we gaze into the night sky, it’s like looking at a projection on a giant dome — we see two-dimensional pictures, with no perception of depth. Even astronomers can have a hard time plotting that third dimension — a difficulty that can skew their understanding of how stars work.

Consider the Coathanger, a pattern of 10 stars that looks like an upside-down coat hanger. It’s in the faint constellation Vulpecula, the fox.

For decades, astronomers thought those stars formed a cluster. A cluster’s stars are all the same age and same distance, and they formed from the same ingredients. But some of its stars are small and light, while others are big and heavy. Seeing how the different weight classes have evolved helps astronomers understand how all stars age.

But a study in 1970 found that only a few of the Coathanger’s stars were related. And a later one, which used a satellite to plot the distances to stars with great precision, found that none of them were related — they just happened to line up in the same direction. So plotting the third dimension robbed the Coathanger of some of its scientific value — but none of its beauty.

The Coathanger is a great target for binoculars. Sweep them from the bright star Altair, which is low in the east at nightfall, toward even brighter Vega, far to its upper left. The Coathanger is about a third of the way along that line — a beautiful grouping that’s not really a group at all.


Script by Damond Benningfield

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