Messier 47

Messier 47 (M47 or NGC 2422) is an open cluster in the constellation Puppis. It was discovered by Giovanni Batista Hodierna before 1654 and independently discovered by Charles Messier on February 19, 1771. It was later independently discovered again, under the current name NGC 2422.

Messier 47
Observation data (J2000.0 epoch)
Right ascension 07h 36.6m[1]
Declination−14° 30′[1]
Distance498 pc[1]
Apparent magnitude (V)4.2
Apparent dimensions (V)30.0′
Physical characteristics
Mass453[1] M☉
Radius10.61 pc[1]
Estimated age78 million years
Other designationsNGC 2422, Cr 152

There is actually no cluster in the position indicated by Messier, which he expressed in terms of its right ascension and declination with respect to the star 2 Puppis. However, if the signs of Messier's coordinate differences are changed, the position matches that of NGC 2422.[2] Until the equivalency of M47 with NGC 2422 was found, M47 was considered a lost Messier Object. The discovery that M47 and NGC 2422 were the same cluster only came in 1959 with a realization by Canadian astronomer T. F. Morris.[3]

M47 is at a distance of about 1,600 light-years from Earth with an estimated age of about 78 million years. The member stars of M47 have been measured down to about red dwarfs at apparent magnitude 19. There are around 500 members,[1] the brightest being HD 60855, a magnitude 5.7 Be star. The cluster is dominated by hot class B main sequence and giant stars, but a noticeable colour contrast comes from several bright red giants.[3]

M47 is located about a degree away from Messier 46, which is much older and much further away.[3]

References
  1. Prisinzano, L; Micela, G; Sciortino, S; Favata, F (2003). "Luminosity and Mass Function of the Galactic open cluster NGC 2422". Astronomy & Astrophysics. 404 (3): 927–938. arXiv:astro-ph/0304321. Bibcode:2003A&A...404..927P. doi:10.1051/0004-6361:20030524.
  2. Houston, Walter Scott (2005). Deep-Sky Wonders. Sky Publishing Corporation. ISBN 978-1-931559-23-2.
  3. "The hot blue stars of messier 47". ScienceDaily. 17 December 2014.


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