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Topic: Globular Cluster M15

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	globular cluster (Site not responding. Last check: 2007-09-07)
		Unlike open clusters and stellar associations, which are held together only weakly by gravity and contain Population I objects, globular clusters are tightly gravitationally bound collections of Population II stars.
		Further evidence that globular clusters are not necessarily relics of the earliest generations of stars in a galaxy comes from observations of galaxy collisions.
		One of the nearest globular clusters, M13 (the Great Cluster in Hercules), was the target for an early attempt at CETI, though whether planets exist within globulars clusters is still a matter of debate.
	www.daviddarling.info /encyclopedia/G/globclust.html (595 words)

	ASP: A Thousand Blazing Suns: The Inner Life of Globular Clusters
		Globular clusters are extremely old - 12 to 16 billion years old - so the most massive "stars" left in clusters today are likely to be compact objects such as neutron stars of about 1.4 solar masses (at or just above the Chandrasekhar mass limit for white dwarfs) and somewhat lower-mass white dwarfs.
		While the cores of globular clusters may be hotbeds of activity, at the outer edges of the clusters' halos, the Milky Way's tidal forces are busily stripping away hapless low-mass stars.
		Their distribution within clusters tends to be more centrally concentrated than that of the red giants; this indicates that the blue stragglers not only formed near the cluster center, but also that their higher masses cause them to segregate to the center.
	www.astrosociety.org /pubs/mercury/9904/murphy.html (3295 words)

	Messier Object 15
		On the other hand, the tidal radius of this globular cluster, beyond which member stars would escape because of the Milky Way galaxy's tidal forces is a bit larger: 21.5 arc minutes, corresponding to a distance of 210 light years from the cluster's center.
		M15 was discovered by Jean-Dominique Maraldi (Maraldi II, 1709-88) on September 7, 1746 while he was looking for De Chéseaux' comet; he described it as 'A nebulous star, fairly bright and composed of many stars'.
		M15 was the first globular cluster in which a planetary nebula, Pease 1 or K 648 ("K" for "Kuster"), could be identified (Pease 1928, on photographic plates taken at Mt. Wilson in 1927).
	www.seds.org /messier/m/m015.html (906 words)

	Globular cluster M15 (Site not responding. Last check: 2007-09-07)
		The globular cluster Messier 15 (NGC 7078) in Pegasus, shown from a 30-second red-light exposure (through clouds) with a Tektronix 2048x2048 CCD at the prime focus of the 4-meter Mayall telescope of Kitt Peak National Observatory.
		M15 is the most popular candidate for seeing a process known as core collapse.
		M15 also contains a planetary nebula (a rarity among globular clusters), nicely shown in this Hubble Heritage image.
	www.astr.ua.edu /gifimages/m15r.html (195 words)

	M15 Globular Cluster in Pegasus
		M15 is among the most conspicuous of the globular clusters.
		M15 is one of the densest of all (globular) star clusters in our Milky Way galaxy.
		Of the 150 known globular clusters within the Milky Way, 21 have been found to contain a collapsed core.
	www.waid-observatory.com /m015-2004-06-14.html (141 words)

	M 15 (Site not responding. Last check: 2007-09-07)
		M15 was discovered by Jean-Dominique Maraldi (Maraldi II, 1709-88) on September 7, 1746 while he was looking for De Cheseaux' comet; he described it as 'A nebulous star, fairly bright and composed of many stars'.
		It is still unclear if the central core of M15 is packed so dense simply because of the mutual gravitational interaction of the stars it is made of, or if it houses a dense, super massive object, which would be resembling the super massive objects in galactic nuclei.
		Moreover, globular cluster M15 contains the considerable number of 9 known pulsars, neutron stars which are the remnants of ancient supernova explosions from the time when the cluster was young.
	www.messiermarathon.com /new_page_21.htm (345 words)

	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 (5132 words)

	Star Clusters
		Globular clusters are particularly useful for studying stellar evolution, since all of the stars in the cluster have the same age (about 15 billion years), but cover a range of stellar masses.
		The pinkish object to the upper left of the cluster's core is a gas cloud surrounding a dying star.
		Globular clusters are among the oldest clusters of stars in the universe.
	www.cosmiclight.com /imagegalleries/starclusters.htm (5396 words)

	M15 - Globular Cluster in Pegasus (Site not responding. Last check: 2007-09-07)
		The Hubble Space Telescope imaged the core of this globular cluster in 1994.
		The Hubble press release indicated that the dense core may be the result of the presence of a massive fl hole at the center of the cluster or the density may be the result of a core collapse.
		This cluster is at a distance of approximately 32,000 light years and is located in the constellation Pegasus.
	www.astroimages.org /ccd/m15.html (141 words)

	M15 Globular Star Cluster
		M15 is a magnitude 6.3 globular star cluster in the constellation Pegasus.
		M15 is a rich compact globular star cluster, and displays a relatively bright central core when viewed through a telescope.
		This star cluster ranks as the 12th brightest globular cluster visible in the sky.
	members.cox.net /sidleach/m15.htm (223 words)

	[No title]
		But if any globular cluster has a fl hole at its center, M15 is the most likely candidate." The team began using Hubble to observe the centers of globular clusters in 1991 and now has data on about twenty clusters, but the images of M15 are by far the most stunning.
		Cluster stars also provide a limit on the age of the universe, independent of the expansion of the universe itself.
		For a gravothermal catastrophe to occur, globular clusters must transfer energy from the inner parts of the cluster to outer regions.
	nssdc.gsfc.nasa.gov /photo_gallery/caption/hst_globclust_m15.txt (1188 words)

	Alpha Centauri's Universe: Exploration Of Globular Cluster M15
		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.
		Comparison of the measured HRD of each globular cluster with theoretical model HRDs derived from the theory of stellar evolution provides the possibility to derive, or estimate, the age of that particular cluster.
		It is perhaps a bit surprising that all the 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.earthandspace.info /contents/file0041b.htm (753 words)

	M15: A Great Globular Cluster
		Globular clusters are a particularly difficult problem for a gravity-only cosmology.
		But from another vantage point, it is not unthinkable that the stars of globular clusters are “just hanging there”, both with respect to the clusters’ own center of gravity and the gravitational center of the galactic disk to which the clusters are symmetrically linked.
		And as for the spherical form of globular clusters, the cosmic electricians suggest that the best analogy may come from something as unfamiliar to astronomers as ball lightning.
	www.thunderbolts.info /tpod/2005/arch05/051216m15cluster.htm (791 words)

	SPACE.com -- Hubble Confirms Middleweight Black Holes Exist
		These globular clusters, as they are called, are thought to contain the oldest stars of the universe.
		Researchers involved in the studies say globular clusters probably had fl holes early in their histories and that they might fill a missing link in the understanding of how their far more massive cousins develop.
		Because that cluster is so far away, however, researchers looked at the combined light of the cluster and inferred from it the velocities of stars.
	www.space.com /scienceastronomy/astronomy/blackhole_cluster_020917.html (1041 words)

	Messier 15 - Wikipedia, the free encyclopedia
		Globular Cluster M15 (also known as Messier Object 15 or NGC 7078) is a globular cluster in the constellation Pegasus.
		The core of this cluster has undergone a contraction known as core collapse and it has a central density cusp (just left of centre in image at right), with an enormous number of stars surrounding what may be a central fl hole.
		There have also been found to be at least 8 pulsars in M15 including one double neutron star system, M15 C. Moreover, M15 houses one of only four planetary nebulae known in a globular cluster, Pease 1, discovered in 1928.
	en.wikipedia.org /wiki/Globular_Cluster_M15 (321 words)

	Astronomy
		Globular clusters are among the oldest known stellar formations.
		Stars within a cluster are by no means the same, there is a wide range of masses which in turn produces many different evolutionary paths within the cluster.
		Age of the cluster can be found by comparring the turn-off point in the CMD of the unknown cluster to the turn-off point in a standard HR Diagram.
	www.macalester.edu /astronomy/research/phys40/M15/M15.html (1521 words)

	Globular Star Clusters
		Charles Messier was the first to resolve one globular cluster, M4, but still referred to the other 28 of these objects in his catalog as "round nebulae." Thus, in summer 1782, before William Herschel started his comprehensive deep sky survey with large telescopes, there were 33 globular clusters known.
		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)

	M15
		M15 is perhaps the densest of all (globular) star clusters in our Milky Way galaxy.
		It is still unclear if the central core of M15 is packed so dense simply because of the mutual gravitational interaction of the stars it is made of, or if it houses a dense, supermassive object, which would be resembling the supermassive objects in galactic nuclei.
		The one in M15 would among the nearest and better observable to us, being only little more remote than the Galactic Center and much less obscured by interstellar matter.
	www.intercom.net /user/shaffer/messier/m15.html (406 words)

	Space & Astronomy News - Black hole mystery uncovered - 24/09/2002
		The Hubble's measurements are based on the velocities of stars whirling around in the dense cores of globular clusters, which yield a direct measurement of fl hole masses.
		The M15 globular star cluster is close enough to permit measurements of individual star speeds.
		If fl holes dwell in the cores of globular star clusters, then theoretically they were in the clusters when they originally formed – unlike the violent cores of some galaxies.
	www.abc.net.au /science/news/space/SpaceRepublish_683538.htm (494 words)

	APOD: 2000 August 4 - M15: Dense Globular Star Cluster (Site not responding. Last check: 2007-09-07)
		In fact, only 40,000 light-years away in the constellation Pegasus, M15 is one of the most densely packed globular star clusters in our Milky Way Galaxy.
		M15 is filled with ancient stars, about 12 billion years old compared to the Sun's estimated 4.5 billion years.
		Unlike most globulars, M15 displays a planetary nebula, the briefly visible gaseous shroud of a dying star.
	antwrp.gsfc.nasa.gov /apod/ap000804.html (191 words)

	The First Interstellar Gas in a Globular Cluster? by Ken Croswell
		M15 is also one of the few globular clusters with a planetary nebula--a bubble of gas that a red giant star sheds when metamorphosing into a white dwarf.
		Theory predicts all the red giants in a globular cluster should produce roughly 100 solar masses of gas before the cluster crosses the Galactic plane.
		Thus, M15 has a gas-to-dust ratio of 600, about 3 times higher than the ratio in the envelope of a red giant with the Sun’s metallicity.
	www.sonic.net /~antares/M15Gas.html (639 words)

	Chandra :: Photo Album :: M15 :: 06 Sep 01
		Chandra's image of a puzzling X-ray source in the globular star cluster M15 shows that it is not one neutron star binary system, but two neutron star binary systems that appear so close together (2.7 seconds of arc) that they were indistinguishable with previous X-ray telescopes.
		Subsequent data from X-ray telescopes indicated that the neutron star itself was not directly visible in X-ray light because it was hidden by an accretion disk of hot matter swirling from a companion star onto the neutron star.
		The broader implication of the Chandra discovery is that binary star systems with a neutron star orbiting a normal star may be common in globular clusters.
	chandra.harvard.edu /photo/2001/m15 (281 words)

	M-15, globular cluster (Site not responding. Last check: 2007-09-07)
		Globular Star Cluster M-15, in the constellation of Pegasus, is one of the dozen or so best examples of this type of object.
		Past studies of the stars in this and other globular clusters using current theories of nuclear fusion, indicate that the cluster is over 10 billion years old.
		While this is older than the current Big Bang theory says is the age of the universe, we at least know that the globular clusters are many billions of years old.
	www.kopernik.org /images/archive/m15.htm (244 words)

	Clustered Heart (Site not responding. Last check: 2007-09-07)
		Among the shifting menagerie lurk the dinosaurs of the universe, globular clusters.
		One of the most crowded of the clusters has also been attracting a host of astronomers to its dazzling heart.
		Globular cluster M15 has been a puzzle to sky gazers since the 1700's, when French comet hunter Charles Messier spotted the cluster as a faint patch of light in the constellation Pegasus.
	scicom.ucsc.edu /scinotes/9601/Globular/00Intro.html (363 words)

	Durrell - Globular Clusters
		As such, globular cluster systems in other galaxies have been used as distance indicators.
		Below is the CMD for M15, in which colours have been added to illustrate positions of blue and red stars in the cluster.
		In this diagram, a stars colour (related to its temperature) is plotted along the bottom axis (where stars towards the right are redder, or cooler, stars), while the magnitude (or brightness) of stars are plotted on the vertical axis -- with the brighter stars located towards the top of the diagram.
	cc.ysu.edu /~prdurrel/Research/Clusters/Clusters.html (671 words)

	Hubble Star Clusters
		The nearest globular cluster to Earth (7,000 light-years away), and containing more than 100,000 stars, M4 was the target of a Hubble Space Telescope search for white dwarf stars.
		M15 is one of nearly 150 known globular clusters that form a vast halo surrounding our Milky Way galaxy.
		The two components of the cluster are both relatively young and consist of a main, globular-like cluster in the center and an even younger, smaller cluster, seen below and to the right, composed of extremely hot, blue stars and, fainter red T-Tauri stars.
	www.utahskies.org /HST/Archives/clusters.html (3343 words)

	HubbleSite - NewsCenter - Hubble Peers Deep into the Crowded Heart of the Densest Known Star Cluster (11/08/1995) - ...
		By pinpointing individual suns in the glare of the most tightly packed cluster of stars in our galaxy, the Hubble telescope has unveiled hints of either a massive fl hole or another remarkable phenomenon: a "core collapse" driven by the intense gravitational pull of so many stars in such a small volume of space.
		Astronomers used the telescope's sharp images to count an extraordinary number of stars in the ancient globular cluster M15, about 37,000 light-years from Earth.
		The fl-and-white picture shows the cluster's central region; the color image is a close-up of the core.
	hubblesite.org /newscenter/archive/releases/1995/06 (236 words)

	Globulars
		Globular cluster M13 is the brightest globular cluster visible from northern temperate latitudes.
		Thus, even the globular cluster, which appears to us the most densely packed mass of stars to be found anywhere in the Universe, is shown to be by earthly standards almost empty space."
		Globular Cluster M3 is about 100,000 light years away in the constellation Canes Venatici.
	faculty.rmwc.edu /tmichalik/globulars.htm (1085 words)

	[No title]
		Rumors are rampant in India and China that the respective Governments have been contacted and the origin of the UFOs and intelligent life form is from this M15 Star Cluster.
		According to some Astrophysicists, this M15 Star Cluster is also the source of largest density of Black Holes and gateway to many Universes.
		The UFO sightings in the earth are either from this Federation of Universe or from the “Local Administrators” from the nearby Star Clusters.
	farshores.org /ufo05i11.htm (568 words)

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