Sky Object of the Month – March 2017
(Courtesy LVAS Observer’s Challenge*)
M67 (NGC 2682) – Open Cluster in Cancer (Mag. 6.9; Size 25’)
Cancer is home to a pair of Messier open clusters. The first, M44, is the large naked eye group that became one of Galileo’s first telescopic targets. The second, M67, is our LVAS Observer’s Challenge for March.
Discovered by the German astronomer Johann Gottfried Koehler in 1779 (some sources say he encountered it a few years earlier), M67 is located a little less than 2 degrees west of Acubens (alpha [a] Cancri). Its faintness when compared to M44 is illusory, as its calculated distance of 2600 light years is five times greater than that of the Beehive.
My first encounter with M67 was on the night of January 11, 1978, when I viewed it with a 3-inch f/10 reflector at 30X. I wrote in my log book, “Faint, ghostly, beautiful; Reminds me of M11. Contains three visible stars attended by a soft glow. Glow bursts into speckles of light with averted vision. General funnel shape.” More recently, I re-observed M67 with the same scope and a higher magnification of 60X. The cluster was better resolved; with a half dozen faint stars surrounded by another dozen or so averted vision stars.
M67 is visible in binoculars as a hazy patch of light, not unlike the naked eye appearance of M44. As already noted, a small-aperture telescope will reveal a handful of cluster members Scopes in the 8 to 12-inch range will capture up to 100 of the cluster’s 500-plus stars.
Being one of the oldest known open star clusters with a calculated age of 4 billion years, M67 is of particular interest to professional astronomers. Along with the Hyades, it’s the most-studied of any open star cluster.
Glenn Chaple for the LVAS
Mario Motta M.D. www.messier-objects.com
*The purpose of the LVAS Observer’s Challenge is to encourage the pursuit of visual observing. It is open to everyone that is interested, and if you are able to contribute notes, drawings, or photographs, the LVAS will be happy to include them in our monthly summary. If you would like to contribute material, submit your observing notes, sketches, and/or images to either Roger Ivester (firstname.lastname@example.org) or Fred Rayworth (email@example.com). To find out more about the LVAS Observer’s Challenge or access past reports, log on to lvastronomy.com/observing-challenge.