Messier 25

Messier 25, also known as IC 4725, is an open cluster of stars in the southern constellation of Sagittarius. The first recorded observation of this cluster was made by Philippe Loys de Chéseaux in 1745 and it was included in Charles Messier's list of nebulous objects in 1764.[6] The cluster is located near some obscuring features, with a dark lane passing near the center.[3]

Messier 25
Observation data (J2000.0 epoch)
Right ascension 18h 31m 47.0s[1]
Declination−19° 07′ 00″[1]
Distance2,000 ly (620 pc)[2]
Apparent magnitude (V)4.9[3]
Apparent dimensions (V)36′[2]
Physical characteristics
Mass1,937 M☉[4] M☉
Radius6.5 light-years[4]
Estimated age67.6 million years[2]
Other designationsMessier 25,[5] IC 4725, Cr 382, C 1828–192, Mel 204

M25 is at a distance of about 2,000 light-years light-years away from Earth and is 67.6 million years old.[2] The spatial dimension of this cluster is about 13 light-years across. It has an estimated mass of 1,937 M☉, of which about 24% is interstellar matter.[4] A Delta Cephei type variable star designated U Sagittarii is a member of this cluster,[7] as are two red giants, one of which is a binary system.[8]

References
  1. 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.
  2. Kharchenko, N. V.; et al. (2005), "Astrophysical parameters of Galactic open clusters", Astronomy and Astrophysics, 438 (3): 1163, arXiv:astro-ph/0501674, Bibcode:2005A&A...438.1163K, doi:10.1051/0004-6361:20042523.
  3. Landolt, Arlo U. (February 1964), "The Galactic Cluster M25", Astrophysical Journal Supplement, 8: 352, Bibcode:1964ApJS....8..352L, doi:10.1086/190093.
  4. Tadross, A. L.; Marie, M. A.; Osman, A. I.; Hassan, S. M. (2002), "Astrometry of the Open Cluster M25", Astrophysics and Space Science, 282 (4): 607–623, Bibcode:2002Ap&SS.282..607T, doi:10.1023/A:1021137115870.
  5. "IC 4725". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 12, 2018.
  6. Thompson, Robert; Thompson, Barbara (2007), Illustrated Guide to Astronomical Wonders: From Novice to Master Observer, DIY science, O'Reilly Media, Inc., p. 408, ISBN 0596526857.
  7. Wampler, J.; et al. (May 1961), "Cepheids in Galactic Clusters. VIII. a Reinvestigation of U SGR in M25 (= IC 4725)", Astrophysical Journal, 133: 895, Bibcode:1961ApJ...133..895W, doi:10.1086/147092.
  8. Mermilliod, J. C.; et al. (September 1987), "Membership of cepheids and red giants in 8 open clusters : NGC 129, 6067, 6087, 6649, 6664, IC 4725, LY 6, RU 79", Astronomy and Astrophysics Supplement Series, 70: 389–407, Bibcode:1987A&AS...70..389M.


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