M 44
Published on Apr 23, 2007 at 5:15 pm.
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Filed under star clusters.
For the next few nights, the Moon will be near the star cluster M44. This star cluster is the 44th object on Messier’s list of things not to confused with comets. It is one of the few star clusters visible to the naked eye. However, it is nowhere near as bright as the Pleiades or the Hyades, which are also in the sky most nights that M44 is up. Also, unlike the Pleiades and Hyades, M44 can not generally be resolved into individual stars to the naked eye, but rather always looks like a small fuzzy patch in the sky (unless viewed with binoculars or a telescope). M44 is dim enough, though, that it would be hard to see it next to the glare of the Moon without optical aid.
M44 is also known as Praesepe (Latin for manger) or the “Beehive” cluster. It is also cataloged in the New General Catalog as NGC 2632. The Praesepe cluster has been known since ancient times. Both Aratus and Pliny report that observing Praesepe can be used to forecast the weather. If the sky looks otherwise clear, but Praesepe can not be seen, then it means that there is a high thin layer of haze, and that forecasts coming storms.
M44 contains several hundred stars. However, with the exception of a blue straggler, none of these are main sequence stars hotter than spectral type A0. From this, we can infer that the cluster is some 730 million years old (the hotter stars die out quicker). Current estimates of its distance range from 780 to 790 lightyears away from us. In apparent size, the cluster stretches 90 to 95 arcminutes across the sky (this is about 3 times the diameter of the Full Moon). At that distance, this means that the cluster is about 20 lightyears in diameter. This means that the stars of M44 are about two dozen times denser than are the stars in the vicinity of our Sun.
-Astroprof
Image courtesy SEDS
