... 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. ...

... Dark Matter Ring Modeled around Galaxy Cluster CL0024+17 . ... It is the relatively weak distortions of the many distant faint blue galaxies all over the image, however, that indicates the existence of the dark matter ring. ... A hypothesis for the formation of the huge dark matter ring holds that it is a transient feature formed when galaxy cluster CL0024+17 collided with another cluster of galaxies about one billion years ago, leaving a ring similar to when a rock is thrown in a pond. ...

This animation shows a galaxy cluster with two mass concentrations (the pink shading indicates the projected mass density) lensing a background field of faint blue galaxies. ... Inside the Einstein ring radius one has radial arcs, and right in the center of the cluster there are demagnified images. The highest magnifications occur at the Einstein ring radius, giving the large tangential arcs. ... Abell 2218 and CL2244-02 are clusters with tangential arcs. ... Tutorial : Part 1 | Part 2 | ...

... The Hydra Cluster of Galaxies . ... 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 . ... Publications with keywords: Hydra - cluster of galaxies . Publications with words: Hydra - cluster of galaxies . ... Illusion and Evolution in Galaxy Cluster Abell 2667 . ...

Gerhardt Meurer (Johns Hopkins University) . The accompanying picture shows NGC 2915, which Australian, Canadian, and American astronomers have shown to be the darkest known disk galaxy. ... The team of astronomers, lead by Gerhardt Meurer at Johns Hopkins University, analyzed the rotation of the galaxy and showed that NGC 2915 is composed mostly of "dark matter". Dark matter is extremely difficult to detect since it does not emit any radiation. ... Gerhardt R. Meurer . ...

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Title: A New Model of the Gravitational Lens 0957+561 and a Limit on the Hubble Constant . Authors: Norman A. Grogin , Ramesh Narayan (Harvard Univ.) ... Title: ROSAT/PSPC observation of the distant cluster CL0939+472 . ... Title: Interaction in the Bimodal Galaxy Cluster A3528 . ... Title: Cosmological Implications of Galaxy Cluster Evolution . ... Title: Galaxy Cluster Virial Masses and Omega . ... Matches 201 to 222 from a total of 222 matches for the search pattern galaxy cluster . ...

Last time we saw that flat rotation curves for galaxies, when measured in galaxies with extended gas distributions, provides unambiguous data that shows the mass distribution is dominated by an unseen, spherical halo. ... Perhaps only galaxies with extended dark matter halos are capable of retaining large gaseous extents? . ... Clusters of Galaxies: . ... The case of the Cancer cluster: . ... Below is the velocity distribution of galaxies in the Cancer cluster: . ... What's going on in Cancer? ...

... Abstract . ... A Survey for Supernovae in Massive High-Redshift Clusters . ... Combined optical and x-ray image of the "Bullet" galaxy cluster: the red outlines the distribution of hot, baryonic gas (from X-rays); the blue maps the underlying (dark matter) mass distribution. ... Galaxy-galaxy lenses, however, offer a distinct advantage, since the background source is extended, and therefore imposes a stronger constraints on the mass distribution of the lensing galaxy than a point-source QSO. ...

Astronotes Armagh Planetarium's Stellar Blog! ... Armagh Planetarium . ... Stars . ... Space Flight . ... Monthly Sky Notes . ... By admin October 1, 2010 Posted in: Stars . A sky of blazing stars (Image Credit: NASA/ESA) . Imagine that once the Sun sets, rather than a dark sky sprinkled with a few thousand dim stars, we had a sky blazing with ten thousand or so stars blazing brighter than Venus. ... Planets orbiting stars in the NGC 3603 Young Cluster would experience just such a sky. ...

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. ...

... Feeding the Monster: Gas Caught in its Death Spiral into a Massive Black Hole . ... Stromlo Professor Mike Dopita have used the Hubble Space Telescope to discover how a massive Black Hole in a nearby galaxy feeds itself. ... Earlier Hubble Telescope data obtained by another team member, Professor Holland Ford of Johns Hopkins University in Baltimore, Maryland, had found a disk of gas rushing around the Black Hole at a speed of 500 kilometers a second. ...

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. ...

... The sample of the Local Volume galaxies (distance smaller than 10 Mpc) gives a unique opportunity to study the properties of galaxies including the weakest objects: the absolute magnitude M B -10 and the virial mass M vir 10 9 M x263C;. ... Luminosity function of the Local Volume galaxies. ... The luminosity functions for galaxies are presented: red dashed line - from the 2dFGRS survey (Norberg et al. 2002); blue dash-dotted line - from the SDSS survey (Blanton et al. ...

... Chandra Observation of DEEP2 Galaxy Groups and Clusters . ... Monday: 'Normal' Galaxies, Tuesday: Cluster Formation and Evolution . ... Statistics of galaxy groups in ultradeep XMM surveys. ... What can multiwavelength observations tell about cluster/group formation as well as galaxy evolution? ... I will present results from a Chandra study of eight low-redshift clusters that has systematically measured the AGN fraction in clusters and describe their spatial, kinematic, and host galaxy...

... STScI-PRC01-04 HUBBLE'S ULTRAVIOLET VIEWS OF NEARBY GALAXIES YIELD CLUES TO EARLY UNIVERSE Astronomers are using these three NASA Hubble Space Telescope images to help tackle the question of why distant galaxies have such odd shapes, appearing markedly different from the typical elliptical and spiral galaxies seen in the nearby universe. ... Light from these galaxies travels great distances (billions of light-years) to reach Earth. ... These stars emit mostly ultraviolet light. ...

The Mass-Density of the Universe and the Distribution of Dark Matter Neta A. Bahcall Princeton University, USA One of the most fundamental questions of cosmology is: How much matter is there in the Universe and how is it distributed? Here we show that several independent measures - including those utilizing clusters of galaxies - all indicate that the mass-density of the Universe is low: only 20-30% of the critical density. ... The results reveal a low den- sity of 0.16+-0.05. ...

... The awsome spectacle of a brilliant comet, with its long ghostly tail streaming behind it, is a rare event. ... Only one other comet, Comet Halley, was seen so far from the Sun, giving scientists an opportunity to watch it as it slowly warmed up and sprouted a tail. ... Comets are the Rip Van Winkles of the solar system -- mini-worlds that have changed little during their 4.5-billion-year nap far from the Sun. ... Observing Comets . ... Once, comets inhabited the entire solar system. ...

AGES observations of Abell1367 and its outskirts Cortese L.1, Minchin R.F.2, Auld R.R.1, Davies J.I.1, Catinella B.2, Momjian E.2, Rosenberg J.L.3, Taylor R.1, Gavazzi G.4, O'Neil K.5 & The AGES Team 1. ... AGES-A1367 Observations Area covered: 5x1 sq. deg. ... Properties of the AGES-A1367 Sample More massive galaxies appear to be redder, have higher surface brightness and lower gas content than dwarf systems, as found in optically selected samples. ...

Next: Ejectors in Massive Binary Previous: Artificial Galaxy: Full Matrix . The first version of the Scenario Machine was aimed especially at the simulation of massive binary star evolution. ... First, there is a large class of intermediate mass binaries (say, consisting initially of 8 + 5 solar masses) that can also produce NS and thus lead to the formation of a bright X-ray source. ... Next: Ejectors in Massive Binary Previous: Artificial Galaxy: Full Matrix Mike E. Prokhorov . ...