Astronomy:IC 4651

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Short description: Open star cluster in the constellation Ara
IC 4651
The rich star cluster IC 4651
Open cluster IC 4651 taken by the Wide Field Imager (WFI) camera, on the MPG/ESO 2.2-meter telescope at ESO’s La Silla Observatory in Chile.[1]
Observation data (J2000 epoch)
Right ascension 17h 24m 49s[2]
Declination−49° 56′ 00″[2]
Distance2,900 ly (888[3] pc)
Apparent dimensions (V)10.0' (arcmin)
Physical characteristics
Other designationsCr 327, Mel 169
See also: Open cluster, List of open clusters

IC 4651 is an open cluster of stars located about 2,900 light years distant in the constellation Ara. It was first catalogued by John Louis Emil Dreyer in his 1895 version of the Index Catalogue.[4] This is an intermediate age cluster that is 1.2 ± 0.2 billion years old.[5] Compared to the Sun, the members of this cluster have a higher abundance of the chemical elements other than hydrogen and helium.[6] The combined mass of the active stars in this cluster is about 630 times the mass of the Sun.[7]

The currently known active stars in this cluster form only about 7% of the cluster's original mass. Of the remainder, about 35% of the mass consists of stars that have evolved into white dwarfs or other stellar remnants. The remainder of lost mass consists of stars that have migrated away from the main body of the cluster or have been lost completely.[7]


  1. "Sibling Stars". 
  2. 2.0 2.1 Xin, Y.; Deng, L. (February 2005). "Blue Stragglers in Galactic Open Clusters and Integrated Spectral Energy Distributions". The Astrophysical Journal 619 (2): 824–838. doi:10.1086/426681. Bibcode2005ApJ...619..824X. 
  3. Dias, W.S.; Alessi, B.S.; Moitinho, A.; Lepine. J.R.D. (July 2002). "New catalog of optically visible open clusters and candidates". Astronomy and Astrophysics 389 (3): 871–873. doi:10.1051/0004-6361:20020668. Bibcode2002A&A...389..871D.  Note: see the VizieR catalogue B/ocl.
  4. Dreyer, J. L. E. (1895). "Index Catalogue of Nebulae found in the years 1888 to 1894, with Notes and Corrections to the New General Catalogue". Memoirs of the Royal Astronomical Society 51: 185–228. Bibcode1895MmRAS..51..185D. 
  5. Biazzo, K. et al. (December 2007). "Deriving temperature, mass, and age of evolved stars from high-resolution spectra. Application to field stars and the open cluster IC 4651". Astronomy and Astrophysics 475 (3): 981–989. doi:10.1051/0004-6361:20077374. Bibcode2007A&A...475..981B. 
  6. Pasquini, L. (September 2004). "Detailed chemical composition of the open cluster IC 4651: The iron peak, α elements, and Li". Astronomy and Astrophysics 424: 951–963. doi:10.1051/0004-6361:20040240. Bibcode2004A&A...424..951P.  This source gives a metallicity value of [math]\displaystyle{ \begin{smallmatrix}\left[\frac{Fe}{H}\right]\ =\ +0.10\ \pm\ 0.03\end{smallmatrix} }[/math], which is equivalent to 125% of the Sun's abundance of Iron.
  7. 7.0 7.1 Meibom, S.; Andersen, J.; Nordström, B. (April 2002). "Critical tests of stellar evolution in open clusters. III. Stellar population and dynamical evolution of IC 4651". Astronomy and Astrophysics 386: 187–203. doi:10.1051/0004-6361:20020183. Bibcode2002A&A...386..187M. 

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