This is a relatively small globular cluster, ranking 112th in luminosity among the Milky Way globular cluster population. It is considered anOosterhoff type I cluster (OoI), despite having a relatively lowmetallicity. Indeed, it has the lowest metallicity of any OoI cluster known. There are 19RR Lyrae variable star candidates and as many as 23blue stragglers. A high proportion of the latter are concentrated near the dense core of the cluster, which is consistent with the idea that blue stragglers form through stellar mergers.[9][10]
The cluster lies some 70.4 ± 7.5 kly (21.6 ± 2.3 kpc) from theGalactic Center,[6] and is relatively isolated from other globular clusters in the galaxy.[9] The position of this cluster makes it a candidate for association with theSagittarius tidal stream, and thus it may have been captured by the Milky Way after separation from theSagittarius Dwarf Spheroidal Galaxy.[6] A contour map of the cluster appears to show S-shaped tidal arms stretching to the north and south for several tidal radii. Such features are predicted for globular clusters that follow elliptical orbits and are near theirapogalacticon.[11]
^Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters",Harvard College Observatory Bulletin,849 (849):11–14,Bibcode:1927BHarO.849...11S.
^abcSkrutskie, Michael F.; Cutri, Roc M.; Stiening, Rae; Weinberg, Martin D.; Schneider, Stephen E.; Carpenter, John M.; Beichman, Charles A.; Capps, Richard W.; Chester, Thomas; Elias, Jonathan H.; Huchra, John P.; Liebert, James W.; Lonsdale, Carol J.; Monet, David G.; Price, Stephan; Seitzer, Patrick; Jarrett, Thomas H.; Kirkpatrick, J. Davy; Gizis, John E.; Howard, Elizabeth V.; Evans, Tracey E.; Fowler, John W.; Fullmer, Linda; Hurt, Robert L.; Light, Robert M.; Kopan, Eugene L.; Marsh, Kenneth A.; McCallon, Howard L.; Tam, Robert; Van Dyk, Schuyler D.; Wheelock, Sherry L. (1 February 2006)."The Two Micron All Sky Survey (2MASS)".The Astronomical Journal.131 (2):1163–1183.Bibcode:2006AJ....131.1163S.doi:10.1086/498708.ISSN0004-6256.S2CID18913331.
^abcdCarballo-Bello, Julio A.; et al. (December 2014), "A search for stellar tidal debris of defunct dwarf galaxies around globular clusters in the inner Galactic halo",Monthly Notices of the Royal Astronomical Society,445 (3):2971–2993,arXiv:1409.7390,Bibcode:2014MNRAS.445.2971C,doi:10.1093/mnras/stu1949.
^Arellano Ferro, A.; et al. (October 2004), "CCD Photometry of the RR Lyrae Stars in NGC4147",Revista Mexicana de Astronomía y Astrofísica,40: 209–221 (2004),Bibcode:2004RMxAA..40..209A.
Media related toNGC 4147 at Wikimedia Commons