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Topic: Galactic cluster

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In the News (Mon 20 Nov 17)

  Keyword Index listing for C   (Site not responding. Last check: 2007-10-21)
New aperture photometry for 217 galaxies in the Virgo and Fornax clusters.
Multicolour photometry of the cluster of galaxies Sersic 129-01 (Millington, S.J.C.+,1989)
Globular clusters 1 and 3 in the Fornax dwarf galaxy (Jorgensen, U.G.+,1997)
xml.gsfc.nasa.gov /archive/KeywordIndexC.html   (4233 words)

 Clusters of Galaxies   (Site not responding. Last check: 2007-10-21)
In clusters the typical mass to light ratio is ~ 400 in units of solar masses divided by solar luminosities.
This cluster, which is 650 million light years distant, is rich in gas and dust and spiral galaxies with robust star formation, but relatively poor in elliptical galaxies.
Thus it is a relatively young cluster of galaxies.
csep10.phys.utk.edu /astr162/lect/gclusters/clusters.html   (254 words)

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Ser., 33, 185 (1978) The metal-poor globular cluster NGC 7099.
Ser., 33, 361-389 (1977) Metal-rich globular clusters in the galaxy.
Soc., 125, 307-312 (1963) The galactic cluster NGC 3228.
www.tass-survey.org /tass/catalogs/loneos.ref   (11526 words)

 Open cluster -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-21)
While most clusters become dispersed before a large proportion of their members have reached the white dwarf stage, the number of white dwarfs in open clusters is still generally much lower than would be expected, given the age of the cluster and the expected initial mass distribution of the stars.
Clusters which have enough mass to be gravitationally bound once the surrounding nebula has evaporated can remain distinct for many tens of millions of years, but over time internal and external processes tend also to disperse them.
Because the stars in an open cluster are all at roughly the same distance from (The 3rd planet from the sun; the planet on which we live) Earth, and were born at roughly the same time from the same raw material, the differences in apparent brightness among cluster members is due only to their mass.
www.absoluteastronomy.com /encyclopedia/o/op/open_cluster.htm   (2786 words)

Clusters of the second type used to be called ‘galactic clusters,’ because we see them inside the body of our galaxy, but now it is more common to refer to them as ‘open clusters’ because they are much looser and their stars more spread out on the sky than are those in globular clusters.
However, if we look at clusters we can disentangle the effects of age from the other variables, since all the stars in a particular cluster (of either type) were presumably formed together at the same time, out of the same material.
Different globular clusters show very similar colour magnitude diagrams to one another, whereas the colour magnitude diagrams for galactic clusters show a considerable variation in the length of the main sequence and the proportion of giants.
www.peripatus.gen.nz /Astronomy/Clusters.html   (1416 words)

 Clusters of Galaxies
It is estimated that the composition of a cluster is 10% galaxies, 20% intracluster medium (gas), and 70% dark matter.
Therefore, either that clusters are systems whose member galaxies became gravitationally bound at more or less the same time, or that the clusters represent condensations from pregalaxian material and that subcondensations within them became galaxies.
One of the cluster formation scenarios suggests that a group of newly formed galaxies (protogalaxy) are expanding away from each other some one billion years or so after the Big Bang.
universe-review.ca /F04-galactic-cluster.htm   (1455 words)

 Chandra Shows Cycle of Hot Gases at Core of Galactic Cluster   (Site not responding. Last check: 2007-10-21)
The phenomenon involves the flow of relatively cool gas into the center of galactic clusters, leaving astronomers guessing as to where it later emerges.
A recent Chandra image shows long strands of 35-million degree gas extending from the center of the cluster, indicating that magnetic fields and explosions near a supermassive fl hole at the core of the galaxy are responsible for pushing the cool gas around.
Galaxy clusters are the largest objects bound together by gravity in the universe and provide clues to the origin and fate of the universe.
www.space.com /news/chandra_hydra_991213.htm   (264 words)

 Open Clusters
In older publications they are usually called ‘galactic clusters,’ because we see them inside the body of our galaxy, but now it is more common to refer to them as ‘open clusters’ because their member stars are much less concentrated than those of globular clusters.
The cluster is believed to be in equilibrium right on the point of falling apart, which explains the loss of all low-mass members of the cluster.
Although clusters are often moved out of the galactic plane by their passage through interstellar clouds or close approaches to other massive bodies, it takes a very long time for the orbital plane to become as inclined as that of NGC 752.
www.peripatus.gen.nz /Astronomy/OpeClu.html   (2145 words)

 Open or Galactic Clusters   (Site not responding. Last check: 2007-10-21)
Open clusters are preferentially found in the plane of the galaxy (thus they are also called galactic clusters); in contrast, the globular clusters are concentrated in the halo of the galaxy and can be very far out of the plane.
In images of open clusters such as this one, not all stars in the field of view are members of the cluster; some are stars between us and the cluster and some are stars beyond the cluster.
The stars in the cluster must all have approximately the same proper motion or the cluster would have dissipated over time, but stars not associated with the cluster would be expected to have more random motions.
csep10.phys.utk.edu /astr162/lect/clusters/open.html   (314 words)

 APOD Search Results for "galactic cluster"   (Site not responding. Last check: 2007-10-21)
galactic halo orbit is a highly eccentric one which, every one or two billion years, brings it relatively close to the galactic center.
The stars in the cluster were formed in a single "burst" of star formation only one or two million years ago, so the x-rays are believed to come from the massive young stars themselves or from their energetic stellar winds.
Since other common galactic sources of x-rays such as supernova remnants and neutron stars represent final stages in the life of a massive star, they are unlikely to be present in such a young cluster.
antwrp.gsfc.nasa.gov /cgi-bin/apod/apod_search?galactic+cluster   (8400 words)

 Open Star Clusters
Over 1100 open clusters are known in our Milky Way Galaxy, and this is probably only a small percentage of the total population which is probably some factor higher; estimates of as many as about 100,000 Milky Way open clusters have been given.
The first open clusters have been known since prehistoric times: The Pleiades (M45), the Hyades and the Beehive or Praesepe (M44) are the most prominent examples, but Ptolemy had also mentioned M7 and the Coma Star Cluster (Mel 111) as early as 138 AD.
All the diffuse nebulae in Messier's catalog are associated with open clusters of young stars which have formed of the nebula's material in (astronomically) very recent times, and are still formed today in many cases.
www.seds.org /messier/open.html   (1098 words)

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The Arches cluster is a factor of six closer to us, resulting in a potential advantage in regards to confusion; however, it is not observable at UV or visible wavelengths because of the thick column of dust between us and the cluster.
The number of O-stars in the case of the Quintuplet and Central clusters is estimated based upon the ages of the clusters and the number of identified post-main sequence stars.
The presumably high metalicity in the Galactic center might also produce a variation in the spectrum of masses formed there with respect to what is observed in the disk of the Galaxy, but it is still not clear if the metalicity in the Galactic center is extrasolar \citep{ram00}.
www.aoc.nrao.edu /~gcnews/gcnews/Vol.18/figer@stsci.edu_Figer.txt   (7033 words)

 Star Clusters
Two main types of star clusters occur: the small and sparse open (galactic) clusters containing tens to thousands of young stars, and the large and dense globular clusters containing up to several million stars.
The fact that the oldest stars and clusters in the galactic disk are about as old as the youngest halo clusters suggests that the galactic disk may have formed
The two teardrop-shaped objects below the cluster toward the bottom of the picture are similar to suspected protoplanetary disks encompassing stars in the Orion Nebula as shown in Figure 07-01.
universe-review.ca /F06-star-cluster.htm   (2480 words)

 Pleiades - Galactic Star Cluster
The Pleiades, the most famous galactic star cluster in the heavens, is a cluster of bright, white stars, all formed at the same time, within a large cloud of interstellar dust and gas in the constellation of Taurus.
A blue haze accompanying the cluster is caused by a very fine dust which reflects the blue light from the stars.
The Aztecs called the cluster Tianquiztli, which means “marketplace.” Aztec time was measured by the movements of the stars and the Sun.
www.thewildrose.net /pleiades.html   (510 words)

 2MASS Atlas Image Gallery
The luminosity functions for globular clusters vary, with metal-rich clusters having flatter function slopes than metal-poor clusters; recent indications are that a cluster's interaction with the Galactic disk could strip lower-mass stars from the cluster, leading to a relative overabundance of higher-mass stars, which would lead to greater enrichment of elements, such as oxygen.
Although the 2MASS imaging and pipeline photometry is not optimized for such crowded regions as globular clusters, because NGC 3201 has a relatively lower concentration of stars, the near-infrared photometry resulting from the pipeline processing reasonably represents the stellar populations in the cluster, as seen in the resulting color-color and color-magnitude diagrams.
The cluster is relatively metal-rich, that is, the abundance of elements heavier than helium is relatively high, possibly as high as the Sun.
www.ipac.caltech.edu /2mass/gallery/images_globs.html   (2086 words)

 galactic cluster on Encyclopedia.com   (Site not responding. Last check: 2007-10-21)
Star factory near galactic center bathed in high-energy X-rays.
The galaxy's oldest stars: differences in the ages of the oldest stars yield clues to Galactic history.(Lives of stars)
Catching a galactic football -- Chandra examines Cygnus A. The galaxy's oldest stars: differences in the ages of the oldest stars yield clues to Galactic history.(Lives of stars)
www.encyclopedia.com /html/x/x-galact-cl.asp   (251 words)

 Motions In Nearby Galaxy Cluster Reveal Presence Of Hidden Superstructure   (Site not responding. Last check: 2007-10-21)
A nearby galaxy cluster is facing an intergalactic headwind as it is pulled by an underlying superstructure of dark matter, according to new evidence from NASA's Chandra X-ray Observatory.
Galaxy Cluster Surveys May Help Explain "Dark Energy" In The Universe (April 24, 2002) -- The universe appears to be permeated with an invisible force -- dark energy -- that is pushing it apart faster and faster.
The motion of the core gas cloud, together with optical observations of a group of galaxies racing inward on a collision course with it, suggests that an unseen, large structure is collapsing and drawing everything toward a common center of gravity.
www.sciencedaily.com /releases/2004/09/040914093037.htm   (771 words)

 [10.08] Chromospheric Activity in Young Galactic Cluster Stars   (Site not responding. Last check: 2007-10-21)
Spectra of the Ca II H and K line region of 80 late-type stars in seven young clusters were examined to obtain estimates of chromospheric activity, projected rotation velocity, radial velocity and spectral type.
The spectra were obtained using the Hydra multi-fiber spectrographs on the Blanco 4-m and WIYN 3.5-m telescopes at the Cerro Tololo Interamerican Observatory and at Kitt Peak.
The clusters ranged in age from the youngest, NGC 2264, at an age of about 3 million years, to the oldest, IC 4664, at an age of about 100 million years.
www.aas.org /publications/baas/v35n5/aas203/954.htm   (251 words)

 APOD: March 5, 1999 - M46 And NGC 2438: Young And Old   (Site not responding. Last check: 2007-10-21)
These swarms of bright stars are born near the plane of the Milky Way, but their numbers steadily dwindle as cluster members are strewn through the Galaxy by gravitational interactions.
This bright open cluster, known as M46, is around 300 million years young and still contains a few hundred stars.
The striking red patch of glowing gas above center in this lovely photograph is the planetary nebula NGC 2438 - a brief, final phase in the life of a solar-type star a few billion years old whose central reservoir of hydrogen fuel has been exhausted.
antwrp.gsfc.nasa.gov /apod/ap990305.html   (189 words)

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Charles compiled a list of over 100 deep-sky objects with the original purpose of providing a resource to identify objects that were often mistaken as comets.
Today, the Messier catalog stands for a collection of almost all of the magnificent deep-sky nebula, galaxies, and star clusters that can be seen through a small amateur telescope.
It contains nearly 8,000 entries of galaxies, nebula, asterisms, star clusters, etc..., and also has its fair share of mislabeled numbers that correspond to a blank area of sky.
members.ncats.net /astro/reference/messier.html   (161 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   (1933 words)

 SPACE.com -- Chandra Captures Gas Plume Escaping Centaurus Galactic Cluster
It may have formed by gas cooling from the cluster onto the moving target of the central galaxy, as seen by Chandra in the Abell 1795 cluster.
Other possibilities are that the plume consists of debris stripped from a galaxy which fell into the cluster, or that it is gas pushed out of the center of the cluster by explosive activity in the central galaxy.
A problem with these ideas is that the plume has the same concentration of heavy elements such as oxygen, silicon, and iron as the surrounding hot gas.
www.space.com /scienceastronomy/astronomy/chandra_centaurus_020130.html   (517 words)

 Ghost of a flea: Galactic cluster foul-up
The event details what the scientists are calling the perfect cosmic storm: galaxy clusters that collided like two high-pressure weather fronts and created hurricane-like conditions, tossing galaxies far from their paths and churning shock waves of 100-million-degree gas through intergalactic space.
Otherwise, the image that comes to mind is an advanced civilization noting the shockwaves (presumably, light moves faster than the gas), and knowing what's coming, and having to decide what to do...
Faced with that awesome wave of doom, even stepping out of the entire galactic cluster may not offer protection - as some of the thermal photos amply demonstrate.
www.ghostofaflea.com /archives/004364.html   (303 words)

 Photometric study of the old galactic cluster Be 31   (Site not responding. Last check: 2007-10-21)
Photometric study of the old galactic cluster Be 31
J/AJ/106/220 J/AJ/106/220 Photometric study of old galactic cluster Be 31
CCD photometry on the Johnson UBV and on the Kron-Cousins VI systems are presented for 732 stars in and near Be 31, an open cluster located towards the galactic anticenter.
www.cs.wisc.edu /niagara/data/nasa/AJ_106_220.xml   (58 words)

 sciforums.com - New type of galactic cluster identified...
As amateur telescope users well know, star clusters in our Milky Way come in two basic types: open clusters and the much richer, denser globulars.
The new class of clusters eluded detection for so long because they don't seem to exist in our Milky Way, and because their surface brightnesses are so low that only the most powerful, modern instruments can find them anywhere else.
Like globulars, the faint extended clusters appear to be made of numerous, old, relatively red stars.
www.sciforums.com /showthread.php?t=6611   (256 words)

 APOD: February 25, 1999 - NGC 6712: Galactic Globular Cluster   (Site not responding. Last check: 2007-10-21)
high above the galactic plane, globular star clusters are probably 12 to 14 billion years old - truly ancient denizens of our Milky Way Galaxy.
gravitational stripping of stars from clusters which pass through the plane and central regions of the Galaxy.
crossed through the crowded galactic plane only a few million years ago.
antwrp.gsfc.nasa.gov /apod/ap990225.html   (166 words)

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