Messier 46

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Messier 46 or M46, also known as NGC 2437, is an open cluster of stars in the slightly southern constellation of Puppis. It was discovered by Charles Messier in 1771. Dreyer described it as "very bright, very rich, very large." It is about 5,000 light-years away. There are an estimated 500 stars in the cluster with a combined mass of Template:Val,<ref name=Piskunov2007/> and it is thought to be a mid-range estimate of 251.2 million years old.<ref name=Wu2009a/>

The cluster has a very broadest (tidal) radius of Template:Convert and core radius of Template:Convert.<ref name=Piskunov2007/> It has a greater spatial extent in infrared than in visible light, suggesting it is undergoing some mass segregation with the fainter (redder) stars migrating to a coma (tail) region. The fainter stars that extend out to the south and west may form a tidal tail due to a past interaction.<ref name=Davidge2013/>

The planetary nebula NGC 2438 appears to lie within the cluster near its northern edge (the faint almost rainbow array of colored smudge at the top-center of the image), but it is most likely unrelated since it does not share the cluster's radial velocity.<ref name=majaess2007>Template:Cite journal</ref><ref name=kiss2008> Template:Cite journal</ref> This makes for superimposed objects of interest, another instance perhaps being NGC 2818.<ref name=majaess2007/><ref name=mermilliod2001> Template:Cite journal</ref> On the other hand, the illuminating star of the bipolar Calabash Nebula shares the radial velocity and proper motion of Messier 46, and is at the same distance, so is a bona fide member of the open cluster.<ref name=vickers2015> Template:Cite journal</ref>

M46 is located close by to another open cluster, Messier 47.<ref name=ScienceDaily-2014-12-17>Template:Cite news</ref> M46 is about a degree east of M47 in the sky, so the two fit well in a binocular or wide-angle telescope field.

See also

• List of Messier objects
• Messier object

External links

• Messier 46, SEDS Messier pages
• Messier 46, Amateur Astronomer Image – Waid Observatory
• Dark Atmospheres Photography – M46 w/ NGC 2438 detail
• Template:APOD
• Template:APOD – featuring M46
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• Template:WikiSky