Messier 46

Coordinates: Sky map 07h 41.8m 00s, −14° 49′ 00″
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Messier 46
Open cluster Messier 46 in Puppis
Observation data (J2000.0 epoch)
Right ascension07h 41m 46.0s[1]
Declination−14° 48′ 36″[1]
Distance4,920 ± 980 ly (1,510 ± 302 pc)[1]
Apparent magnitude (V)6.0[2]
Apparent dimensions (V)22.8[3]
Physical characteristics
[3] M
Radius37.8 ly[3]
Estimated age251.2[1] Myr
contains superimposed
planetary nebula NGC 2438
Other designationsM64, NGC 2437, Cr 159, C 0739-147, OCl 601.0[4]
See also: Open cluster, List of open clusters

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 453 M,[3] and it is thought to be a mid-range estimate of 251.2 million years old.[1]

The cluster has a very broadest (tidal) radius of 37.8 ± 4.6 ly (11.6 ± 1.4 pc) and core radius of 8.5 ± 1.3 ly (2.6 ± 0.4 pc).[3] 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.[5]

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.[6][7] This makes for superimposed objects of interest, another instance perhaps being NGC 2818.[6][8] 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.[9]

M46 is located close by to another open cluster, Messier 47.[10] 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[edit]


  1. ^ a b c d e Wu, Zhen-Yu; et al. (November 2009), "The orbits of open clusters in the Galaxy", Monthly Notices of the Royal Astronomical Society, 399 (4): 2146–2164, arXiv:0909.3737, Bibcode:2009MNRAS.399.2146W, doi:10.1111/j.1365-2966.2009.15416.x, S2CID 6066790.
  2. ^ "Messier 46". SEDS Messier Catalog. Retrieved 29 April 2022.
  3. ^ a b c d e Piskunov, A. E.; et al. (June 2007), "Towards absolute scales for the radii and masses of open clusters", Astronomy and Astrophysics, 468 (1): 151–161, arXiv:astro-ph/0702517, Bibcode:2007A&A...468..151P, doi:10.1051/0004-6361:20077073, S2CID 14769639.
  4. ^ "M 46". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 25 November 2018.
  5. ^ Davidge, T. J. (February 2013), "The Open Cluster NGC 2437 (Messier 46)", Publications of the Astronomical Society of the Pacific, 125 (924): 115–125, arXiv:1301.6806, Bibcode:2013PASP..125..115D, doi:10.1086/669823, S2CID 118656815
  6. ^ a b 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. S2CID 18640979.
  7. ^ 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 (1): 399–404. arXiv:0809.0327. Bibcode:2008MNRAS.391..399K. doi:10.1111/j.1365-2966.2008.13899.x. S2CID 15207860.
  8. ^ 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 & Astrophysics. 375: 30–39. Bibcode:2001A&A...375...30M. CiteSeerX doi:10.1051/0004-6361:20010845. S2CID 122773065.
  9. ^ 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.
  10. ^ "The hot blue stars of messier 47". ScienceDaily. 17 December 2014.

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