Exploring Spring Deep Sky Objects

© 1997 by Robert C. Moler

Deep sky objects are dim wonders of the heavens beyond the solar system. They are star clusters, nebulae and galaxies. Star clusters and nebulae belong to our galaxy the Milky Way, and for the most part lie in or near the milky band. Checking the Star and Planet Chart for this month, the Milky Way band lies low in the north for the most part. This means that nebulae and star clusters are few. The ones we do see are either close to the milky band or close to us.

As a matter of fact one of the closest star clusters to us, appears farthest from the band of the Milky Way. It's near the galactic pole. That is the cluster and the constellation called Coma Berenices.

Coma Berenices translates into Berenice's Hair. To the unaided eye which just barely resolves the stars here the array of stars do take on the appearance of strands of hair. The cluster is actually larger than the binocular field of view. Coma Berenices lies about 250 light years away, so it is still not really far from the galactic plane. Who knows, it might be closer to the galactic plane than we are. The cluster contains about 37 stars from 5th to 11th magnitude. It is possible that the cluster is slowly breaking up. While about the size as the famous Pleiades of autumn, but with about a third the stars, so the mutual gravitational pull of the stars may not be enough keep the cluster together.

Coma Berenices has other clusters including a few dim globular clusters, the brightest of which is M53. (The designation means it was 53rd object on the list of faint objects in the catalog of Charles Messier, who was really looking for comets.) But one of its Come Berenices' clusters in not a cluster of stars, but of galaxies called the Coma Cluster. Here lie a thousand galaxies the lie at a distance of 400 million light years. Only two of these galaxies can be seen with amateur telescopes.

There are quite a few other galaxies within the area assigned to Coma Berenices by astronomers. These are outlying members of the large and much closer Virgo Cluster of galaxies. which lies a mere 65 million light years away. One of the most prominent of these is M100, which the Hubble Space Telescope used to refine the age of the universe by measuring the brightness and periods of its Cepheid variable stars. My attention was brought to it about 20 years ago when a supernova appeared among its stars. Another beautiful galaxy which is an edge-on spiral is NGC4565. (NGC is the New General Catalog, which is now not so new because it's 100 years old.)

The heart of the Virgo Cluster of galaxies lies in western part of the constellation Virgo and left of the haunches of Leo. These galaxies are fodder for telescopes 8 inches in diameter and up. After searching in vain for these galaxies with a 5 inch telescope in my youth, i was amazed by the numbers of then found with an 8 inch telescope I completed in the 12th grade. Even without a finder telescope, I was able to find and identify them by their location to each other. It was quite an extraordinary feeling. The central monster galaxy of the bunch is M87 a giant elliptical galaxy, which I understand eats other galaxies for lunch.

One of the really neat members of the Virgo Cluster is M104, seen just above the constellation of Corvus the crow. Its is nicknamed the Sombrero. This edge-on spiral galaxy has a large nucleus, and really reminds one of that particular form of a hat. Three other far flung members of the cluster are M65, M66 and NGC 3628 located under the triangle of Leo's haunches.

To the west of Leo lies the faint constellation of Cancer. It lies closer to the band of the Milky Way than the constellations discussed so far. In it are two remarkable star clusters. The first is M44, also known as Praesepe (manger) or the Beehive cluster. This cluster is located in the central part of Cancer. To the unaided eye it appears as a fuzzy spot, but shows its true nature in binoculars. Its 200 stars lie at a distance of 525 light years.

In the south of Cancer lies one of the oldest open clusters, and one which is physically quite far from the galactic plane. This is M67 which can be spotted in binoculars as a fuzzy spot. In the telescope it is a rich and compact cluster that is 2500 light years away and 1500 light years from the plane of the Milky Way. M67 contains more than 500 stars, and its brightest are red giants, meaning that this is an old cluster. The vast majority of open clusters are young, whose brightest stars are blue-white. The calculated age of M67 is about 10 billion years, which make it around the age of globular star clusters.

The current controversy about the age of the universe can best be seen with the Hubble results M100 which tend to imply an age of the universe 10 billion years or less and star clusters like M67 and globulars with an age of 10 billion years or more. As we understand it a star cannot be older than the universe. The conflict between the two age estimates will be resolved. It will be exciting to see how it turns out.


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Uploaded: 05/08/97