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Topic: Globular Cluster M71

	Globular cluster - Wikipedia, the free encyclopedia
		Globular clusters, which are found in the halo of a galaxy, contain considerably more stars and are much older than the less dense galactic, or open clusters, which are found in the disk.
		It does appear clear that globular clusters are significantly different from dwarf elliptical galaxies and were formed as part of the star formation of the parent galaxy rather than as a separate galaxy.
		"The ellipticities of Galactic and LMC globular clusters".
	en.wikipedia.org /wiki/Globular_cluster (5116 words)

	Messier 71 - Wikipedia, the free encyclopedia
		Messier 71 (also known as M71 or NGC 6838) is a globular cluster in the constellation Sagitta.
		M71 is at a distance of about 12,000 light years away from Earth and spans some 27 light years across.
		The shortness of the branch explains the lacking of the RR Lyrae variables and is due to the globular's relatively young age of 9-10 billion years.
	en.wikipedia.org /wiki/Globular_Cluster_M71 (225 words)

	Roaming the Deep Sky #5
		This unusual and distinctive globular cluster, can be found along the eastern edge of the Summer Triangle (formed by Deneb, Vega and Altair), about halfway between Altair and Albireo (the beautiful double star which marks the head of Cygnus, the Swan).
		M71 is about 12,000 light years from the sun and is currently 22,000 light years from the galactic center.
		M71, H20, and an asterism led by 9 Sagittae (Sge) are all visible in this 50’ field.
	home.insightbb.com /~lasweb/lessons/RDS05-M71.htm (649 words)

	Globular Cluster Encyclopedia Article @ Gazed.org (Site not responding. Last check: 2007-10-21)
		The globular cluster NGC 6528 is visible in the lower left corner.
		The kinematics of globular clusters, apocentric distances and a halo metallicity gradient.
		The Stellar Population of the Globular Cluster M 3.
	www.gazed.org /encyclopedia/Globular_cluster (4819 words)

	Globular Star Cluster M71 (NGC6838) (Site not responding. Last check: 2007-10-21)
		In comparison with usual globular clusters like M 10, its star distribution is very loose but on the other hand the cluster is much more rich and condensed than typical open clusters like NGC 2194.
		The old age of 15 Gyrs is typical for galactic globular clusters, but the abundance of heavy elements (metallicity) is as high as in galactic plane objects like open clusters.
		Finally, Zinn (1985) introduced an intermediate class of globular clusters that belong to the galactic plane population and not as usual to the spherical distributed halo population.
	www.allthesky.com /clusters/m71.html (196 words)

	Globular Star Clusters - Information and Observations
		Globular clusters are the senior citizens of our galaxy - they contain suns at least 12 billion years old.
		Summer nights are the best time to start hunting for globular clusters, almost one third of them are to be found in the summer constellation of Sagittarius.
		For your first observation of a globular cluster choose M13, the brightest cluster visible from the northern sky, teetering on the edge of naked-eye visibility and appearing as a small, hazy glow in binoculars.
	www.nightskyinfo.com /globular_clusters (661 words)

	M-71, globular cluster
		This class of "disk population globular clusters" includes the famous southern sky cluster NGC 104 (47 Tucanae).
		Spectra show that the cluster stars are metal-rich, which does not support the classification as a globular.
		According to a study of various clusters by T.Kinman (1957) the distance is probably about 18,000 light years; the full diameter of about 6' then corresponds to about 30 light years.
	www.kopernik.org /images/archive/m71.htm (439 words)

	Flickr: Photos from JMZawodny
		Globular Cluster M56 The four different globular clusters I imaged last night are presented here to...
		Globular Cluster M15 The four different globular clusters I imaged last night are presented here to...
		Globular Cluster M13 The four different globular clusters I imaged last night are presented here to...
	www.flickr.com /photos/jmzawodny (280 words)

	Globular Clusters
		Thus as we look toward the central regions of the galaxy in the summer many more globular clusters are apparent than in the winter when night skies direct our gaze away from the center toward the outer reaches of the Milky Way.
		Not surprisingly, the Messier globular clusters tend to be the brightest ones which can be seen from northern latitudes.
		According to the figures in Deep Sky 2.0, this is the sixth brightest globular cluster in the sky.
	home.insightbb.com /~lasweb/lessons/globular.htm (1554 words)

	Globular Star Clusters
		Globular clusters are gravitationally bound concentrations of approximately ten thousand to one million stars, spread over a volume of several tens to about 200 light years in diameter.
		Globular clusters typically contain a number of variable stars, in particular RR Lyrae stars which were once called "Cluster Variables" because of their abundance in globulars.
		It is perhaps a bit surprising that almost all globular clusters seem to be of about the same age; there seems to be a physical reason that they all formed in a short period of time in the history of the universe, and this period was apparently long ago when the galaxies were young.
	www.seds.org /messier/glob.html (2112 words)

	Globular Star Clusters
		Globular clusters are dense groups of stars that formed together and are held in the cluster by gravitational attraction to all the others stars.
		Globular clusters are not contained within the flattened disk of our galaxy, the Milky Way.
		The great average distance to globular clusters (we are about 28,000 light years from the Milky Way’s center) and large densities of stars in their cores lead to globulars appearing as fuzzy patches in telescope eyepieces.
	astronomy.luther.edu /globulars.htm (292 words)

	Sea and Sky's Astronomy Resources: Messier Objects M71 - M80
		This is an extremely loose cluster, and for some time there was doubt as to whether this was a globular cluster at all.
		At a distance of 60,000 light years, it is one of the the most remote globular clusters in the Messier catalog.
		This cluster has a diameter of around 90 light years and is located roughly 36,000 light years from the Earth.
	www.seasky.org /astronomy/astronomy_messier_71to80.html (1028 words)

	Cosmic Voyage-The Online Resource for Amateur Astronomers (Site not responding. Last check: 2007-10-21)
		M71 is another Messier object that suffers from proximity to a more impressive member of that catalog.
		This small globular cluster splits the distance between 3.5 magnitude Gamma and 3.7 magnitude Delta Sagittae.
		M71 is moderately bright as globular clusters go, shining at 8.4 magnitude.
	hometown.aol.com /billferris/m71hop.html (155 words)

	M 71 (Site not responding. Last check: 2007-10-21)
		For a long time, the classification of M71 as a globular cluster was uncertain, many astronomers thought it was a rather condensed open cluster, similar to M11,
		This globular cluster is easy to find and nicely observable even in good binoculars, by locating the 6th-mag star 9 Sagittae half-way between Gamma and Delta of that constellation.
		The cluster is brighter and sharply terminated on the western side, forming a "curving V", as Mallas describes it.
	www.messiermarathon.com /new_page_77.htm (261 words)

	Astroprof’s Page » Globular Clusters
		Globular clusters are generally much farther away than open clusters, such as the Pleiades, also known as M45 (I was originally going to explain all this M-stuff, but I changed my mind, so that I will save for a later blog).
		This is because globular clusters lie outside the plane of the galaxy’s disk.
		Given that globular clusters are relics of the days of the formation of our galaxy, the study of globulars can lead to an interesting insight into the early Milky Way.
	astroprofspage.com /archives/140 (938 words)

	The Chemistry of Stars - Student Projects
		IR Spectroscopy of M71 Giants: One test of whether or not a cluster star has mixed material to its surface during the later stages of evolution is the presence of relatively large amounts of the 13C isotope in its atmosphere.
		The clusters that have been studied to date are for obvious reasons, among the easiest/simplest ones to observe/analyze - i.e., close by with little dust in the way.
		Other, more metal-rich clusters are out there, but they are in the direction of the galactic center, making them harder to study (mostly due to the effects of dust).
	www.phys.uwosh.edu /mike/projects.html (1007 words)

	[No title]
		A globular cluster is a collection of tens of thousands to hundreds of thousands of stars, all orbiting around their common center of mass, packed within a region several parsecs in radius.
		If the cluster were rotating, then the velocities would not be isotropic: there would be a preferred direction, perpendicular to the axis of rotation.
		Use the virial theorem to estimate the mass of the cluster, in solar masses.
	spiff.rit.edu /classes/phys440/lectures/glob_clus/glob_clus.html (826 words)

	M71 (Site not responding. Last check: 2007-10-21)
		In 1943 he found that M71 was more resembling a loose globular like M68 (class X) or NGC 5053 (class XI), but in 1959 he took a Color-Magnitude Diagram which he found more similar to that of an open galactic cluster.
		It seems that the high metallicity is connected with a low number of RR Lyrae stars: None could be found in M71 (nor in M69), which has only 8 known variables at all.
		According to newer sources (e.g., W.E. Harris' globular cluster data file), it is 11,700 light years distant.
	www.intercom.net /user/shaffer/messier/m71.html (303 words)

	M71 Globular Star Cluster (Site not responding. Last check: 2007-10-21)
		M71 is an 8th magnitude rich and compact star cluster in the tiny constellation Sagitta, and is the only Messier object found in that constellation.
		It is considered to be a globular star cluster, although it does not have a dense central compression typically found in most globulars and the stars are metal-rich.
		M71 was probably first observed by J.G. Koehler in 1775.
	members.cox.net /~k5xi/m71.htm (146 words)

	NCKAS Globular Clusters
		Globular cluster, extremely bright, very rich in stars, very gradually extremely compressed middle, stars of magnitude 11 and fainter; = M13.
		Globular cluster, bright, very large, round, gradually very much brighter middle, well resolved, stars of magnitude 10 to 15; = M10.
		Globular cluster, bright, very large, round, extremely rich in stars, very gradually much brighter middle, well resolved, stars of magnitude 15; = M14.
	www.nckas.org /globularclusters (997 words)

	star2000 - Dynamics of Star Clusters and the Milky Way
		Deep BV photometry for about 15000 stars in the globular cluster M71 has been obtained from the 2.2m University Hawaii Telescope using 2k CCD.
		From the fitting of the CMD fiducial sequence to the New Yale Isochrone and the similar metallicity globular cluster 47 Tuc, we estimated the absolute and relative ages of this "disk population" globluar cluster.
		We discuss the implications of this on recent HST results about low mass main-sequence stars' lumisoty function and on dynamical evolution of the globular cluster.
	www.ari.uni-heidelberg.de /star2000/abstracts/p_yim.html (173 words)

	Astronomical Observations
		I observed this Globular with the 254mm Dobsonian.
		This Globular Cluster is quite large and is very bright.
		This is a easily seen, fairly small Globular Cluster in the constellation of Coma Berenices.
	www.angelfire.com /space/observations/globular.html (260 words)

	Globular Clusters, by Jim Scala
		Globular clusters, like leaves of a maple tree, are all the same, and yet each one is different.
		In contrast, the galactic cluster represented by M29 is a grouping of stars—a “knot” of stars in the stellar backdrop.
		Until 1946, M71 was listed as a galactic cluster because it appears more like a close group of stars, but after careful analysis, it took its place as a globular cluster only 8,500 light years away.
	www.eastbayastro.org /2000/0900/r0900-8.htm (941 words)

	M71 (Site not responding. Last check: 2007-10-21)
		The classification of M71 as globular cluster has been disputed for a long time, since its condensation is rather low for its class, it might also have been a dense open star cluster.
		Additionally, the cluster's color-magnitude diagram indicates a relatively young age, and high metallicity, both are unusual for a globular cluster of the Milky Way.
		However, newer investigations of the cluster's core density suggest a categorization as a young and loose globular.
	astro.nightsky.at /Photo/GlobClu/M71_MN.html (187 words)

	Observational Data for Galactic Globular Clusters
		The stars at the turnoff in globular clusters are close to the Sun's temperature and mass.
		Interpreting colour-magnitude diagrams for clusters in terms of a star's evolutionary history remains a central problem for astrophysics even 75 years after the first diagrams were constructed and their significance shown.
		In visual observation of a globular cluster, obviously if you are going to see any resolution at all, your telescope will have to show stars at least as faint as the brightest stars in the cluster.
	www.ngcic.org /papers/gctext.htm (2654 words)

	M71 Globular Cluster in Sagitta
		It was classified by early astronomers as a dense open cluster but resent consensus is that M71 is a "loose" globular cluster.
		It is small for a globular with a visible diameter of approximately 27 light years.
		It lies at a distance of approximately 13,000 light years from the Earth and can be viewed under dark skies with the aid of binoculars.
	www.waid-observatory.com /m071-2004-05-23.html (116 words)

	Messier Objects 51-110 (Site not responding. Last check: 2007-10-21)
		M71 is one of the nearest globular clusters at 8,500 lty away.
		This cluster is as bright as M13, also in Hercules, but it is twice as small.
		M107 Globular Cluster in Ophiuchus.M107 is a 9th magnitude cluster about 10,000 lty away.
	www.ess.sunysb.edu /observer/mess2.html (421 words)

	M71 (Site not responding. Last check: 2007-10-21)
		This cluster, which looks like a barely visible star-knot in the city and suburbs, is impressive from dark skies only due to its marvelously rich field.
		M71 is famous as the globular cluster that wasn't.
		For years, astronomers argued as to whether this was an open or globular star cluster.
	skywatch.brainiac.com /deepweb/m71.htm (201 words)

	M71 - Globular Cluster (Site not responding. Last check: 2007-10-21)
		M71 (NGC 6838) is a globular cluster in the constellation Sagitta.
		This cluster is estimated to be located 11,700 light years away.
		More information and additional images of this cluster can be found at the Messier Index - M71.
	www.astroimages.org /ccd/m71.html (75 words)

	The Frequency of Binary Stars in the Globular Cluster M71 (Site not responding. Last check: 2007-10-21)
		A comparison of the frequency of binaries in globular clusters with those in the field halo and disk populations tests the similarity of star formation in those environments.
		Binary stars in globular clusters also act as an energy source which ``heats" the cluster through super-elastic encounters with other stars and binaries.
		We have used the KPNO 4-m and the multi-fiber instruments Nessie and Hydra to measure radial velocities at 4 epochs over two years for a sample of 126 stars in the globular cluster M71.
	www.aas.org /publications/baas/v26n4/aas185/abs/S10419.html (327 words)

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