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Home » Deep Sky Highlights
At this time of year, the summer constellations have faded and are being replaced by the winter constellations. High in the southern sky is Pegasus and Andromeda while Cygnus is retreating to the west, Auriga and Taurus are rising in the east. Here are some popular deep sky objects for this time of year.
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M15 - Globular Cluster in Pegasus
A globular cluster is a system of about one million stars that together orbit a galaxy. One of the brightest globular clusters in our Milky Way galaxy is the pictured M15, the fifteenth object on Messier's list of diffuse objects on our sky. Most stars in globular clusters are older and redder than our Sun, which is about 5 billion years old. (Image: Electronic Universe Project)
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M31 - The Andromeda Galaxy
Andromeda is the nearest major galaxy to our own Milky Way Galaxy. Our Galaxy is thought to look much like Andromeda. Together these two galaxies dominate the Local Group of galaxies. The diffuse light from Andromeda is caused by the hundreds of billions of stars that compose it. The several distinct stars that surround Andromeda's image are actually stars in our Galaxy that are well in front of the background object. Andromeda is frequently referred to as M31 since it is the 31st object on Messier's list of diffuse sky objects. M31 is so distant it takes about 2 million years for light to reach us from there. (Image: Electronic Universe Project)
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M45 - The Pleiades Star Cluster
The Pleiades star cluster, M45, is one of the brightest star clusters visible in the northern hemisphere. It consists of many bright, hot stars that were all formed at the same time within a large cloud of interstellar dust and gas. The blue haze that accompanies them is due to very fine dust which still remains and preferentially reflects the blue light from the stars. (Image: Mount Wilson Observatory)
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The Hyades
At a distance of only about 150 light years, the Hyades are the nearest open cluster to us in the constellation Taurus. The brightest star in the field of the Hyades, bright red giant star Aldebaran, is not a member of the cluster and situated much closer to us (only 60 light years). The central group is roughly 10 light years in diameter, while outlying members seem to be spread over a volume of at least 80 light years diameter. (Image: Till Credner and Sven Kohle)
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NGC 869 and NGC 884 - The Double Cluster
Most star clusters are singularly impressive. But open clusters NGC 869 and NGC 884 are doubly impressive. Also known as "h and chi Persei", this rare double cluster, shown above, is bright enough to be seen from a dark location without even binoculars. Although their discovery surely predates written history, the "double cluster" was notably cataloged by the Greek astronomer Hipparcos. The clusters are over 7000 light years distant toward the constellation of Perseus, but are separated by only hundreds of light years. (Image: Andy Steere)
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