Magnifying PowerJuly 13, 2009 What might at first appear to be giant blue space amoebas invading a cluster of galaxies is actually a unique example of the power of gravitational lensing to multiply and magnify a distant galaxy. In this image, taken by the Hubble Space Telescope and analyzed by Adi Zitrin and Tom Broadhurst, a cluster of galaxies (the bright yellow-white objects) has lensed a much more distant (blue) spiral galaxy into 5 magnified copies of itself-- seen here in the (1) upper left, (2) lower right, and (3-5) just below and slightly right of the center. The inset box shows a computer generated model of the unlensed source galaxy, enlarged by a factor of four so that the details, including the spiral arm structure, are visible. Without the lensing power of the cluster, we would see this galaxy as a single small blue smudge. For a more detailed discussion of this image, see Guest Post: Evalyn Gates on Cosmic Magnification (or -- Invasion of the Giant Blue Space Amoebas) at Cosmic Variance.
Big MACS CollisionAugust 27, 2008
The Chandra X-ray Observatory and Hubble Space Telescope have captured the cosmic collision of two giant clusters of galaxies. This collision is similar to that seen in the Bullet Cluster, providing further evidence for dark matter. Overlaid on the Hubble image of MACS J2005.4-1222 is the X-ray gas (hot pink) detected by Chandra, and the total mass determined using gravitational lensing (blue). The separation of gas from the bulk of the mass occurred during the high-speed collision of the two clusters, and indicates that most of the mass in the clusters is in the form of invisible dark matter. See the Chandra website for details.