Regular readers of my column know that constellations are impossible to see.
For many years I’ve seen folks disappointed when they begin to do stargazing and can’t find a lion or a hunter or a bear in the sky.
There’s a good reason for this: The images aren’t there!
Constellations are simply areas of the sky that the ancients set up to represent objects, animals and people, but at no time did these ever resemble anything.
Don Hall, former planetarium director of the Strasenburgh Planetarium in Rochester, New York, frequently explained that constellations look no more like their namesakes than the George Washington Bridge looks like the father of our country.
But what about the patterns we do see, like the Big Dipper, the Northern Cross, or the Square of Pegasus?
Of course, it’s pretty easy to find patterns among the randomly distributed stars — patterns that we recognize as geometrical figures, letters, numbers and even punctuation marks.
But these are not “constellations.” They are “asterisms”: groups of stars that our imaginations form into images we recognize.
If we search long enough, we can find some remarkable asterisms.
This week, while the moon isn’t illuminating our evening sky, head outdoors after dark and search for one of my favorite asterisms: the Coat Hanger.
To find it, face east and locate the three bright stars of the Summer Triangle (another asterism) midway up in the sky. The brightest of the three is Vega, followed by Altair and Deneb.
Once you’ve found the triangle, look along its southwestern side, about one-third of the way from Altair to Vega. If you have a dark sky and good vision, you might spot what appears to be a faint smudge of light.
It was first described 1,060 years ago by the Persian astronomer al-Ṣūfī in his Book of Fixed Stars. Of course, he had no idea what he was seeing, but he found it remarkable enough to record its existence.
Modern stargazers have a huge advantage over al-Ṣūfī; we can aim binoculars in its direction to see what’s really going on there.
If we do this, we can see 10 faint stars that outline the shape of a tiny coat hanger — a straight line of six with a hook on one side formed by four stars.
While we may perceive it as a coat hanger, astronomers know this collection of stars as Collinder 399 or, less formally, as Brocchi’s Cluster.
Whether or not it is a star cluster is a matter of debate. Back in the 1970s and ’80s, astronomers believed many of its stars seemed to be moving together in the same direction and at the same speed as if part of a stellar family we know as a star cluster.
Today, however, we think differently. Measurements made by the European Space Agency’s Hipparcos satellite in the early 1990s suggest that these stars are not moving together as a cluster.
Instead, they seem to be separated by hundreds of light years and appear to be drifting through space in arbitrary directions and speeds.
Whatever we call it — Collinder 399, Brocchi’s Cluster or the Coat Hanger — it’s one cool sight on warm summer nights!
