Roaming the Deep Sky #14
M34
By Don Clouse
M34 is a large, bright, open cluster in the fall constellation Perseus. This 180 million-year-old cluster is some 1,400 to 1,600 light years away. Nearly all the brightest stars in this cluster are of spectral types B9 through A2. Apparently 180 million years is enough time for all the hotter, more massive, stars (O1 through B8) to have burned themselves out in one fashion or another. Its distance and (rough) galactic longitude of 145 degrees, put M34 near the outer edge of our Local Spiral Arm segment and a little ahead of us in our orbits around the Milky Way. In 1983, astronomer O.J. Eggen studied the motion of several star clusters. He identified a "Local Association" of clusters including M34, the Pleiades, NGC2516, IC2602, the Alpha Persei Cluster (Melotte 20), and the Delta Lyrae Cluster (Stephenson 1) moving in similar orbits around the galaxy – although, they have yet to complete one full lap since they are all relatively young clusters. Being interested in such things, I took a few minutes to locate these clusters on the sky. Let’s begin far around the sky in Carina. There we find NGC2516 and IC2602 (the Southern Pleiades), both trailing us in orbit around the Milky Way. IC2602 is only 480 light years away while NGC2516 is 1,100 light years distant. The Delta Lyrae Cluster is, of course, in Lyra and is 800 light years away. This cluster is well ahead of us in orbit and leads this pack of clusters around the galaxy. M34 (1,500 light years) and Melotte 20 (600 light years), both in Perseus, have a slight lead on us in our race around the galaxy but have a longer lane to run being further from the center of the galaxy than we are. And finally, a little further in our eastward sweep around the plane of the galaxy, we come to the Pleiades. The Pleiades are nearly even with us at a galactic longitude of 170 degrees and only 375 light years away. So given their distances and locations, I’d guess that these clusters are strung along some 3,000 light years of the Local Spiral Arm – with us passing through their midst. With a very rough "area" of some 3,000 by 2,000 light years, this seems to be a very loose and scattered association. But, back to M34. M34 is 14 to 18 light years in diameter and subtends at least 35’ on the sky while sporting a rather gaudy magnitude of 5.2. Indeed, it is supposed to be visible to the naked eye under good sky conditions. I have not, however, seen it by naked eye – but hope to this fall!
It is, of course, a very rewarding target for your telescope too, especially in a wide field of view. M34 is located roughly midway between Algol (Beta Persei) and Almaak (Gamma Andromedae). As seen on the chart, it’s a little closer to Algol and a bit north of the Algol-Almaak line. Once located, start out with your lowest power or widest field eyepiece. I’ve logged two observations of this object. On both occasions I used a Celestron 35mm Ultima eyepiece. This yields a 51’ field at 58x. Though the cataloged size of this cluster is 35’ (larger than the full moon!), it seemed to me to extend almost to the edge of the 51’ field. I estimated 100 stars, of widely varying brightness, contained in the field of view. The cluster is moderately concentrated toward the center. A close, bright, pair of stars occupies the center with several other close pairs nearby. The cluster displays a number of short chains and arcs. One long chain runs from the south side of the cluster toward the east. This is an altogether lovely cluster – well worth spending several minutes on.
With only two log entries, this is definitely an object which I hope to observe again this fall. This cluster, by virtue of its size and brightness, should look especially nice in a wide field of view. I’m looking forward to trying a 40mm 2" eyepiece on M34. In my main telescope (Celestron 8" SCT) the 40mm will yield 51x with a 73’ field of view. The view in an 80mm short tube refractor, or any wide field instrument (big binoculars would be nice), should be very attractive as well. M34 is on my fall observing list. Consider putting it on yours. It’ll certainly make a nice target for the Twin Lakes Star Party! Clear, dark skies!
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