|Observation data (J2000.0 epoch)|
|Right ascension||07h 41.8m|
|Distance||5.4 kly (1.7 kPc)|
|Apparent magnitude (V)||6.1|
|Apparent dimensions (V)||27.0′|
|Notable features||contains superimposed|
planetary nebula w:NGC 2438
|Other designations||NGC 2437|
Messier 46 (also known as M 46 or NGC 2437) is an w:open cluster in the w:constellation of w:Puppis. It was discovered by w:Charles Messier in w:1771. Dreyer described it as "very bright, very rich, very large." M46 is about 5,500 w:light-years away with an estimated age on the order of several 100 million years.
The w:planetary nebula NGC 2438 appears to lie within the cluster near its northern edge (the faint smudge at the top center of the image), but it is most likely unrelated since it does not share the cluster's radial velocity. The case is yet another example of a superposed pair, joining the famed case of w:NGC 2818. 
M46 is about a degree east of M47 in the sky, so the two fit well in a binocular or wide-angle telescope field.
- Majaess D. J., Turner D., Lane D. (2007). In Search of Possible Associations between Planetary Nebulae and Open Clusters, PASP, 119, 1349
- Kiss, L. L., Szabó, Gy. M., Balog, Z., Parker, Q. A., Frew, D. J. (2008). AAOmega radial velocities rule out current membership of the planetary nebula NGC 2438 in the open cluster M46, MNRAS
- Mermilliod, J.-C., Clariá, J. J., Andersen, J., Piatti, A. E., Mayor, M. (2001). Red giants in open clusters. IX. NGC 2324, 2818, 3960 and 6259, A&A