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Anne’s Picture of the Day: Star Cluster Messier 46
read more at Anne’s Astronomy News http://annesastronomynews.com/
April 6, 2013
Messier 46, a star cluster in Puppis
Image Credit & Copyright: Roth Ritter, Dark Atmospheres Astrophotography (http://www.darkatmospheres.com/astro)
Messier 46 (also known as NGC 2437) is an open cluster of about 30 light-years across, located some 5,400 light-years away in the southern constellation of Puppis, while it is receding from us at 41.4 kilometers per second.
The cluster, with an estimated age of 300 million years, is very rich, with a total population of over 500 stars, including 150 stars brighter than magnitude 13. The brightest of these stars are each about 100 times more luminous than the Sun.
A special and famous feature – visible as a bluish round object a little below and left of the center in this image – is a planetary nebula known as NGC 2438 which appears to lie within Messier 46. However, this nebula is most probably not a true member but is superimposed, or perhaps a passing “guest”.
We know this because NGC 2438 lies a lot closer to us, at only about 2,900 light-years distance, and does not share the cluster’s radial velocity (it is receding from us at the higher speed of about 77 kilometers per second). This means that the planetary nebula is a physically unassociated foreground object which just happens to be in the same direction.
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2013-04-06 05:34:49
Source: http://annesastronomynews.com/annes-picture-of-the-day-star-cluster-messier-46/
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