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Hubble Illuminates Cluster Of Diverse Galaxies



*Description*: Evident from the Hubble image is the fact that ESO 325-G004 is home to thousands of globular clusters, small compact groups of hundreds of thousands of stars that are gravitationally bound systems. These clusters are dispersed spherically and uniformly in the outer halo of the elliptical and make their way around the center of the galaxy over the course of millions of years. Several foreground stars and background galaxies are also visible within the halo of this bright galaxy. In the course of analyzing this Hubble image, astronomers discovered that the galaxy ESO325-004 is actually a "gravitational lens." This means that the focusing power of the enormous mass making up the galaxy causes the light from some background object, probably a distant "dwarf" galaxy, to be deflected and magnified. As a result, the more distant galaxy appears brighter, and distorted into the shape of an arc, or ring, known as an "Einstein ring" because the phenomenon was first predicted by Albert Einstein. Although the universe is filled with galaxies, gravitational lensing is a rare occurrence because it requires an almost perfect alignment of a distant galaxy with an intervening one that has enough mass to gravitationally focus the light. This particular system is unique because it is closest known example of strong gravitational lensing. The galaxy is close enough that the dynamics of its stars can be studied in detail using spectrographs on large ground-based telescopes. The spectrographs reveal how fast the stars in the galaxy are moving, and this allows astronomers to estimate how much mass must be present in the center of the galaxy. This estimate can in turn be compared to the amount of mass needed to produce the observed gravitational lensing effect. In this way, astronomers can build up a detailed, self-consistent picture of the matter distribution and dynamics of this unique nearby lensing system. Technical facts about this news release: About the Object Object Name: ESO 325-G004, Abell S0740 Object Description: Giant Elliptical Galaxy and its Host Galaxy Cluster Position (J2000): R.A. 13h 43m 33s.30 Dec. -38° 10' 34".0 Constellation: Centaurus Distance: Approximately 463 million light-years (142 Megaparsecs) Dimensions: This image is roughy 2.9 arcminutes (385,000 light-years or 120 kiloparsecs) wide. About the Data Data Description: The Hubble image was created from HST data from proposal 10429: PI: J. Blakeslee (Washington State University), J. Lucey and R. Smith (University of Durham), J. Tonry (University of Hawaii), and S. Mei (Johns Hopkins University); and 10710: K. Noll, H. Bond, C. Christian, L. Frattare, F. Hamilton, Z. Levay, M. Mutchler, W. Januszewski, and T. Royle (Hubble Heritage Team/STScI), and J. Blakeslee (Washington State University). Instrument: ACS/WFC Filters: F475W ("g"), F625W ("r"), and F814W ("I") Exposure Date(s): January 2005/February 2006 About the Image Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) Release Date: February 6, 2007 Color: This image is a composite of many separate exposures made by the ACS instrument on the Hubble Space Telescope using several different filters. Three filters were used to sample broad wavelength ranges. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: F475W ("g") blue F625W ("r") green F814W ("I") red Orientation: Hubble Illuminates Cluster of Diverse Galaxies [ http://imgsrc.hubblesite.org/hu/db/2007/08/images/a/formats/compass_large_web.jpg ] What is Hubble Heritage? A monthly showcase of new and archival Hubble images. Go to the Heritage site. This NASA Hubble Space Telescope image shows the diverse collection of galaxies in a galaxy cluster called Abell S0740, located more than 450 million light-years away in the constellation Centaurus. The giant elliptical galaxy ESO 325-G004 looms large at the cluster's center. This galaxy is as massive as 100 billion suns. Hubble resolves thousands of globular star clusters orbiting ESO 325-G004. Globular clusters are compact groups of hundreds of thousands of stars that are gravitationally bound together. At the galaxy's distance they appear as pinpoints of light contained within the diffuse halo. Other elliptical and spiral galaxies appear in the image. The photo was made from images taken using Hubble's Advanced Camera for Surveys in January 2005 and February 2006. *News Release Number:*: STScI-2007-08b


LICENZA : Pubblico dominio
ARGOMENTI : # in Matematica e scienze / Astronomia
TAG : tag: ESO 325-G004 , Abell S0740 , Hubble Space Telescope (HST) , ESO , FAST , Constellation , Centaurus , Advanced Camera for Surveys , Washington , Hawaii , Hamilton
FONTE : Hubble Space Telescope Collection