... 2001 April 16 . The Hydra Cluster of Galaxies . ... Explanation: The Hydra Cluster of Galaxies contains well over 100 bright galaxies - but perhaps fewer galaxies than might be expected from its mass. ... Most of a cluster's mass , however, appears to be in a form too dark to see , as analyses of the distribution of X-ray light , gravitational lensing , and internal motions indicate. ... The Hydra Cluster of Galaxies, named for its home constellation , spans about ten million light years . ...

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• APOD: 2007 April 15 - M3: Inconstant Star Cluster
• APOD: 2004 October 12 - M3: Inconstant Star Cluster
• APOD: 2012 April 3 - M46 and M47: Star Clusters Young and Old

... Credit: D. F. Malin , AAO Explanation: Many stars like our Sun were formed in open clusters. The above open cluster, M11 , contains thousands of stars and is just over three thousand light years distant. ... Open clusters , also called galactic clusters, contain fewer and younger stars than globular clusters. ... Publications with keywords: cluster - M1 - M11 - open cluster . Publications with words: cluster - M1 - M11 - open cluster . ... M45: The Pleiades Star Cluster . ...

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• M11: The Wild Duck Cluster
• Астронет > Wild Duck Open Cluster M11
• Open Cluster M25

... 2000 August 4 . M15: Dense Globular Star Cluster . ... 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. This stunning Hubble Space Telescope image of M15 shows thousands of individual stars across the central 10 or so light-years of the cluster, also cataloged as NGC 7078. ... Globular star clusters harbor from a hundred thousand up to a million stars and roam the Milky Way halo. ...

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• APOD: October 18, 1999 - NGC 3603: An Active Star Cluster
• APOD: December 13, 1997 - The Coma Cluster of Galaxies
• APOD: July 7, 1999 - M80: A Dense Globular Cluster

... Kalirai and Harvey Richer of the University of British Columbia led the study, which began as an investigation of a globular star cluster in the Milky Way galaxy known as NGC 6397. ... Within the population of stars and galaxies behind NGC 6397, the Hubble image revealed a large elliptical galaxy that contains several hundred globular clusters. ... In fact, a single giant star in NGC 6397 appears 10 million times brighter than one of the distant globular clusters. ...

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• http://www.stsci.edu/~marel/abstracts/psdir/AAS197_76_04.ps
• http://www.stsci.edu/~jkalirai/PressStarClustersAstronomy.pdf
• Surface Brightness Profiles

... Bad Astronomy . ... Bitesize Astronomy . ... Last week's Snack talked about how black holes can affect the environment around them in such a way as to be very bright . ... It's a common misconception that black holes always have matter swirling into them. ... As this matter gets closer and closer to the black hole it piles up and a large, fairly flat disk forms. This is called the accretion disk , because matter from this disk accretes (that is, falls in) on the black hole. ... 2008 Phil Plait. ...

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... BLUE STRAGGLER STARS are unusually hot and bright stars found in the cores of ancient star clusters known as globulars. ... BACKGROUND (from wikipedia): Blue straggler stars are stars in open or globular clusters that are hotter and bluer than other cluster stars having the same luminosity. ... There is evidence in favor of this view, notably that blue straggler stars appear to be much more common in dense regions of clusters, especially in the cores of globular clusters. ...

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• Gary Da Costa's Preprints Page

Stellar Clusters are very useful laboratories for empirically studying stellar evolution. ... All cluster stars are at the same distance . All cluster stars have the same physical age . ... CM diagram Young Cluster In this case we see the Main Sequence fully represented. The blue dots represent massive stars with short main sequence lifetimes. ... Thus, identifying the most massive star which is still on the main sequence is an effective means of determining the age of a stellar cluster. ...

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• The Galaxy Gallery Page IX: Clusters of Galaxies
• Astro-2 and the UIT Experiment
• The Galaxy Gallery: Messier Objects

... The Pleiades star cluster, also known as the Seven Sisters and Messier 45, is a conspicuous object in the night sky with a prominent place in ancient mythology . ... The stars in the Pleiades are thought to have formed together around 100 million years ago, making them 1/50th the age of our sun, and they lie some 130 parsecs (425 light years ) away. ... Data for these stars are listed in a table below. ... Yes . ... WEBDA Pleiades cluster data . ... M45: The Pleiades Star Cluster (2007 November 18) ...

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• Pulsar Highlights - A Dozen new MSPs in Globular Clusters
• What is HISA?

... 87.1083Owen+ VIII/29 1400-MHz Survey of 1478 Abell Clusters of Galaxies (Owen+ 1982) ================================================================================ A 1400-MHz Survey of 1478 Abell Clusters of Galaxies Owen F.N., White R.A., Hilldrup K.C., Hanisch R.J. =1982AJ.. ... 0,] Major axis error 70- 71 A2 --- n_MajAxi *[ A, B, C,NR, ] Major axis note 73- 74 I2 arcmin MinAxi *? ... Note on dist-C: Ratio of the distance of the source from the cluster center to the corrected Abell cluster...

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• Sources in Abell clusters
• A 20 cm VLA survey of Abell clusters of galaxies
• Clusters of Galaxies

Astronotes Armagh Planetarium's Stellar Blog! ... Comets and Asteroids . ... Image credit:ESO/J.Emerson/VISTA. ... However others are less pessimistic and it has even been claimed that the mysterious ?Wow! signal? received in 1977 originated from the direction M55.б  Sadly, this still unexplained pulse of radio energy originated from a location rather to the northwest of M55 so I doubt if the source was this cluster (if indeed the signal was genuinely of extraterrestrial origin). ... Mysterious Wow! ...

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• NGC4666: Secrets of a Starburst Galaxy | Astronotes
• Omega Centauri: globular cluster of 300,000 stars | Astronotes
• Leonid meteors 2011 | Astronotes

... Astronomers experienced the same thing, only this time they photographed a dwarf galaxy , and a globular cluster blocked the view. ... A globular cluster is a collection of old stars that orbits a galaxy. ... This particular globular cluster is orbiting the Milky Way our home galaxy. ... Light travels faster than anything in the world, so you could say that this cluster is enormous! ... Astronomers are lucky that the globular cluster insisted on being on camera, as they can now study it in detail. ...

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• http://www.eso.org/public/news/eso1243/kids/
• http://www.eso.org/public/news/eso1519/kids/
• The bright star clusters Messier 47 and Messier 46 in the constellation of

Results from 6m telescope observations of globular clusters in dwarf galaxies Sharina M. We consider properties of globular clusters in dwarf galaxies observed with the multi-slit unit of the SCORPIO spectrograph at the SAO 6m telescope. ... Studying GCs in dwarf galaxies at the faintest end of the galaxy luminosity function provides valuable information for a better understanding of galaxy evolution and evolutionary connection between globular clusters and nuclei of galaxies. ...

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• http://jet.sao.ru/jet/~goray/838/v838ecl.htm

... LMC Project Outline . NGC 1818 Initial Results . ... The Large Magellanic Cloud (LMC) is uniquely suitable for the study of massive star clusters at all stages of evolution. By combining HST observations of these clusters with N-body models we hope to understand the origin and evolution of rich star clusters in our own Galaxy, in the LMC, and beyond. ... We aim to combine our HST observations with N-body models to understand the formation and evolution of globular clusters. ...

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• ESLAB 2007

... This paper ( Burke et al. 2003 ) describes the creation of one such catalogue - the Southern Serendipitous High-redshift Archival ROSAT Cluster (SHARC) survey - which covers an area of 17.7 deg 2 and consists of 32 clusters with redshifts between 0.05 and 0.7 and X-ray luminosities between 7 x 10 42 and 4 x 10 44 erg/s: the high-redshift subsample contains 16 clusters with = 0.3 and X-ray luminosities greater than 2 x 10 43 erg/s (luminosities are quoted for the 0.5 - 2.0 keV energy band). ... 1997 ...

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• The AstroStat Slog Globular Clusters
• The AstroStat Slog Blog Archive my first AAS. IV. clustering
• The galaxy M100

Searching for Ultra Compact Binaries in Globular Clusters What Are Ultra Compact Binaries? ... An ultra compact binary is a binary that consists two white dwarf To source the FITS files that contained the UV images, the sky coordinates stars and has an orbital period shorter than ~70min (A binary and the details on brightness for each star in each globular cluster we were consists of two stars orbiting around their centre of mass, it enables investigating, we used the XMM online archive. ...

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• Armagh Observatory
• JLE Dreyer
• William Herschel

home publications > mercury . ... Big Clusters, Tiny Galaxies . ... Astronomers struggle to understand why giant star clusters form in the tiniest of galaxies . ... These clusters are probably young versions of globular clusters, but they are commonly called super star clusters. Seven dwarf galaxies within 16 million light-years have formed super star clusters, with one of these galaxies, NGC 1569, possessing two young clusters. ... Super star clusters have a lot to tell us about star formation. ...

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• ASP: Star Science in the Autumn Sky
• ASP: Globular Clusters and Satellite Galaxies: Companions to the Milky Way
• ASP: An Ancient Universe - Pleiades

This long-exposure Hubble Space Telescope image of massive galaxy cluster Abell 2744 is the deepest ever made of any cluster of galaxies. ... It contains several hundred galaxies as they looked 3.5 billion years ago. The immense gravity in Abell 2744 acts as a gravitational lens to warp space and brighten and magnify images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did longer than 12 billion years ago, not long after the Big Bang. ...

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• http://www.astronomy.com/sitefiles/resources/image.aspx?item=%7B428E8A98-7EBF-463C-BF9C-866153AC6749%7D
• http://www.astronomy.com/sitefiles/resources/image.aspx?item=%7B45E9FEDA-BA85-4BC6-9E20-E2EF0B096758%7D
• Globular star clusters survive 13-billion-year-old massacre | Astronomy.com

... About ATNF overview . ... Parkes | ... A star cluster is a group of stars that share a common origin and are gravitationally bound for some length of time. ... The two basic categories of stellar clusters are open clusters, also known as galactic clusters, and globular clusters. ... Open clusters are so-named due to the fact that the individual component stars are easily resolved through a telescope. ... M67, a very old open cluster has no star hotter than +0.4 colour index left on the main sequence...

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• Compact Stellar Systems in the Fornax Cluster: Super-massive Star Clusters or
• RV Tau Variables in Globular Clusters - clues on their nature?
• The HIPASS Bright Galaxy Catalog

ATMoB "Open Cluster Observing Award " Guidelines Purpose: To promote observing among the membership of the Amateur Telescope Makers of Boston through participation in the Open Clusters Observing Awards program. Introduction: This awards program is oriented towards visually observing open clusters above magnitude 9.9. ... It turns out that a very unprejudiced and convenient method to dermine the limiting magnitude is to count the number of visible stars in certain areas on the sky. ...

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• Amateur Telescope Makers of Boston ATMoB Observing Awards Program
• Amateur Telescope Makers of Boston

You Can Make Stellar Images Brighter . Articles | ... A few months ago I wrote an article titled "You Can’t Make Them Brighter". So why am I now writing that you can make them brighter. ... The image of a focused star is actually a small disk called the Airy disk, named after the 19 th century scientist Sir George Airy. ... For a given aperture, a smaller Airy disk means that the light is focused to a smaller disk and is therefore brighter. ... www.astronomy.net . About Astronomy Net | ...

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• The Astronomy Shop - Books - by Astronomy Net
• Articles written by astronomers for astronomers of all ages.