Messier Index/M22

Messier 22 250px Core of Messier 22 w:J2000 VII 18 36 24.21SIMBAD Astronomical Database Results for NGC 6656 http://simbad.u-strasbg.fr/Simbad 2006-11-15 -23 54 12.2 10.6 ± 1.0 kly 3.3 ± 0.3 kpcMonaco, L.; Pancino, E.; Ferraro, F. R.; Bellazzini, M. Wide-field photometry of the Galactic globular cluster M22 Monthly Notices of the Royal Astronomical Society 2004 349 4 1278–1290 http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004MNRAS.349.1278M 10.1111/j.1365-2966.2004.07599.x +6.17 32′.0 Sagittarius 105 to 106 50 ± 5 lydistance × sin( diameter_angle / 2 ) = 50 ly. radius 14.2 12 GyrGaudi, B. Scott Interpreting the M22 Spike Events The Astrophysical Journal 2002 566 1 452–462 http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002ApJ...566..452G 10.1086/338041 One of four globulars knownto contain a planetary nebula. NGC 6656, GCl 99 Messier 22 (also known as M22 or NGC 6656) is an elliptical w:globular cluster in the w:constellation Sagittarius near the w:Galactic bulge region. It is one of the brightest globulars that is visible in the night sky. thumb|left|400px|w:Globular Cluster Messier 22 - Courtesy Hunter Wilson History M22 was one of the first globulars to be discovered in w:1665 by w:Abraham Ihle and it was included in Charles Messier's catalog of w:comet-like objects on June 5, w:1764. It was one of the first globular clusters to be carefully studied first by w:Harlow Shapley in w:1930. He discovered roughly 70,000 stars and found it had a dense core. Shapley, Harlow The Mass-Spectrum Relation for Giant Stars in the Globular Cluster Messier 22 Harvard College Observatory Bulletin 1930 874 4–9 http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1930BHarO.874....4S Then w:Halton Arp and w:William G. Melbourne continued studies in w:1959.Arp, H. C.; Melbourne, W. G. Color-magnitude diagram for the globular cluster M22 The Astronomical Journal 1959 64 28 http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1959AJ.....64...28A 10.1086/107848 Because of the large color spread of its w:red giant branch (RGB) sequence, which is similar to that observed in w:Omega Centauri, it became the object of intense scrutiny starting in w:1977 with w:James E. Hesser et al.Hesser, J. E.; Hartwick, F. D. A.; McClure, R. D. Cyanogen strengths and ultraviolet excesses of evolved stars in 17 globular clusters from DDO photometry Astrophys. J., Suppl. Ser. 1977 33 471 http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1977ApJS...33..471H 10.1086/190438 Characteristics M22 is one of the nearer globular clusters to w:Earth at a distance of about 10,600 w:light-years away. It spans 32' on the sky which translates to a spatial diameter of 99 ± 9 light-years. 32 w:variable stars have been recorded in M22. It is projected in front of the galactic bulge and is therefore useful for its w:microlensing effect on the background stars in the bulge. Despite its relative proximity to us, this w:metal-poor cluster's light is limited by w:dust extinction, giving it an apparent magnitude of 5.5 making it the brightest globular cluster in the norther hemisphere.I. Ivans, C. Sneden, G. Wallerstein, R. P. Kraft, J. E. Norris, J. P. Fulbright, and G. Gonzalez On the Question of a Metallicity Spread in Globular Cluster M22 (NGC 6656) Societa Astronomica Italiana 2004 75 286 http://sait.oat.ts.astro.it/MSAIt750204/PDF/2004MmSAI..75..286I.pdf#search=%22%22NGC%206656%22%20red%20giant%22 Planetary Nebula M22 is very unusual in that it is one of only four globulars (the others being M15, w:NGC 6441 and w:Palomar 6) that are known to contain a w:planetary nebula (PN). It was discovered using the w:IRAS satellite by w:Fred Gillett et al.,in 1986 as a pointlike source (w:IRAS 18333-2357)Gillett, F. C.; Neugebauer, G.; Emerson, J. P.; Rice, W. L. IRAS 18333-2357 - an unusual source in M22 Astrophysical Journal, Part 1 (ISSN 0004-637X), w:NASA-supported research. w:January 15 w:1986 300 722–728 http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1986ApJ...300..722G 10.1086/163846 and subsequently identified as a PN in 1989 by Gillett et al.Cohen, J. G.; Gillett, F. C. The peculiar planetary nebula in M22 Astrophysical Journal, Part 1 (ISSN 0004-637X), Research supported by w:California Institute of Technology w:November 15 w:1989 346 803–807 http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1989ApJ...346..803C 10.1086/168061 The PN's central star is a blue star. The PN (designated w:GJJC1) is estimated to be a mere ~6,000 years old. External links Messier 22, SEDS Messier pages Messier 22, Galactic Globular Clusters Database page References