LikeMessier 54 (the other extragalactic globular onMessier's list), it is believed to not be native to theMilky Way galaxy at all, but instead to the putativeCanis Major Dwarf Galaxy, which is currently experiencing a very close encounter with our galaxy. This is, however, a contentious subject as astronomers are still debating the nature of the Canis Major dwarf galaxy itself.[8] Messier 79 may also be part of theGaia Sausage.[9]
Thiscolor-magnitude diagram was made using near-infrared images of the cluster inJ and K bands. J-band magnitude is plotted along the y-axis and J to K dominant color is plotted along the x-axis. Such a diagram is made rapidly with specialized code for crowded-field photometry.[11]
From this, it is evident that most of the bright stars in this cluster are red giants. The elongated branch is thered giant branch. Some of the stars in the diagram, including those extending outward from the red giant branch toward the upper left, are actually foreground stars that are not members of the cluster.
Altogether three regions of theHertzsprung–Russell diagram are present here: the low-mass end of themain sequence, the complete red giant branch and thehorizontal branch. Compared to optical bands, in infrared bands the lower main sequence is shallower and the horizontal branch is steeper (the blue end is fainter and the red end is brighter).
^Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters",Harvard College Observatory Bulletin,849 (849):11–14,Bibcode:1927BHarO.849...11S
^Carballo-Bello, Julio A.; Martínez-Delgado, David; Navarrete, Camila; Catelan, Márcio; Muñoz, Ricardo R.; Antoja, Teresa; Sollima, Antonio (2017), "Tails and streams around the Galactic globular clusters NGC 1851, NGC 1904, NGC 2298 and NGC 2808",Monthly Notices of the Royal Astronomical Society,474:683–695,arXiv:1710.08927,doi:10.1093/mnras/stx2767
^This diagram was made byAstromundus students attending lectures and a workshop by Peter Stetson, the writer of DAOPHOT, standard code for crowded-field photometry. Date: June 2011,University of Rome Tor Vergata
