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Asterisms
updated: Mar 23, 2013, 2:00 PM
By Chuck McPartlin
Because our brains have a superb capability for pattern matching, we
often see familiar things in random assemblages, like silhouetted faces
on the mountains and dinosaurs in the clouds.
Constellations are a great example of this phenomenon, and it also applies
to smaller groupings of stars, called asterisms. Here are a couple of
asterisms visible in backyard telescopes this month; one setting in the
western sky, and one rising in the southeast.
This first asterism is in the constellation Orion, in his club, and is
officially named NGC 2169, since it is entry number 2,169 in the New General
Catalog of astronomical objects. This catalog dates back to William Herschel's
list of observations from the late 1700s. But NGC 2169 has another, unofficial
name and number to amateur astronomers. Because of its appearance, it's called
the 37 cluster.
NGC 2169 is a gravitationally bound group of relatively young stars about
3600 light years away. Relatively young in an astronomical sense means an
age of about 50 million years.
The second asterism is in Corvus, the Crow. Corvus is much smaller and dimmer
than Orion, and to me, it looks more like what Polynesian seafarers called
it - the mast and sail. Dedicated consumers see it as a slightly distorted
shopping cart with a pebble blocking the front wheel.
This asterism is called the Stargate. Its stars are far enough from each
other that it is probably only lightly bound, if at all, and it is more
likely just a random lineup from our point of view, between 250 and
500 light years distant. This asterism was named the Stargate because of
its resemblance to the Stargates used for space travel in the Buck Rogers
serials.
References for a Cloudy Day
NGC 2169
Stargate
History of the Stargate Cluster
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