|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′|
|Estimated age||300 million years|
|Notable features||contains superimposed
planetary nebula NGC 2438
|Other designations||NGC 2437|
Messier 46 (also known as M 46 or NGC 2437) is an open cluster in the constellation of Puppis. It was discovered by Charles Messier in 1771. Dreyer described it as "very bright, very rich, very large." M46 is about 5,500 light-years away. There are an estimated 500 stars in the cluster, and it is thought to be some 300 million years old.
The 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. It is an example of a superimposed pair possibly similar to that of NGC 2818. 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.
- Majaess D. J.; Turner D.; Lane D. (2007). "In Search of Possible Associations between Planetary Nebulae and Open Clusters". Publications of the Astronomical Society of the Pacific 119 (862): 1349. arXiv:0710.2900. Bibcode:2007PASP..119.1349M. doi:10.1086/524414.
- "The hot blue stars of messier 47". ScienceDaily. 17 December 2014.
- Kiss, L. L; Szabó, Gy. M; Balog, Z; Parker, Q. A; et al. (2008). "AAOmega radial velocities rule out current membership of the planetary nebula NGC 2438 in the open cluster M46". Monthly Notices of the Royal Astronomical Society 391: 399. arXiv:0809.0327. Bibcode:2008MNRAS.391..399K. doi:10.1111/j.1365-2966.2008.13899.x.
- Mermilliod, J.-C; Clariá, J. J; Andersen, J; Piatti, A. E; et al. (2001). "Red giants in open clusters. IX. NGC 2324, 2818, 3960 and 6259". Astronomy and Astrophysics 375: 30. Bibcode:2001A&A...375...30M. doi:10.1051/0004-6361:20010845.
- Vickers S.B.; Frew D.J.; Parker Q.A.; Bojicic I.S. (2015). "New light on Galactic post-asymptotic giant branch stars - I. First distance catalogue". Monthly Notices of the Royal Astronomical Society 447 (2): 1673. arXiv:1403.7230. Bibcode:2015MNRAS.447.1673V. doi:10.1093/mnras/stu2383.