NASA Astronomy Picture of the Day Collection
Giant Cluster Bends, Breaks Galaxy Images
What are those strange blue objects? Many are images of a "single, " unusual, beaded, blue, ring-like galaxy [ http://antwrp.gsfc. ] which just happens to line-up behind a giant cluster of galaxies. [ http://antwrp.gsfc. ] Cluster galaxies here appear yellow and -- together with the cluster's dark matter [ http://antwrp.gsfc. ] -- act as a gravitational lens [ http://antwrp.gsfc. ]. A gravitational lens can create several images of background galaxies, analogous to the many points of light one would see while looking through a wine glass at a distant street light. The distinctive shape of this background galaxy -- which is probably just forming -- has allowed astronomers to deduce that it has separate images at 4, 8, 9 and 10 o'clock, from the center of the cluster. [ http://www.aas.org/ ] Possibly even the blue smudge just left of center is yet another image! This spectacular photo from HST [ http://antwrp.gsfc. ] was taken in October 1994. The first cluster lens [ http://antwrp.gsfc. ] was found unexpectedly by Roger Lynds (NOAO [ http://www.noao.edu/ ]) and Vahe Petrosian [ http://bigbang.stan ] (Stanford [ http://bigbang.stan ]) in 1986 while testing a new type of imaging device. Lensed arcs around this cluster [ http://www.stsci.ed ], CL0024+1654, were first discovered from the ground by David Koo (UCO Lick [ http://www.ucolick. ]) in 1988.
Credit and Copyright:
Goddard Space Flight Center (GSFC)
Hubble Space Telescope (HST)
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