Hubble spies shells of sparkling stars around quasar

These sharp images taken with the NASA/ESA Hubble Space Telescope reveal at least five shells of stars surrounding a brilliant quasar at the heart of a giant elliptical galaxy. The image at left shows the quasar, known as MC2 1635+119, and its host galaxy [centre] against a backdrop of distant galaxies.

In the image at top, right, the shells can barely be seen because of the bright light from the central quasar.

The image at bottom, right, was enhanced to reveal details of the faint shells. In both right-hand images, the objects below and to the left of the shells are background galaxies. A foreground star resides at top, left.

The shells have never been seen before in this galaxy, located about 2 billion light-years away. They are evidence that the giant galaxy clashed with another galaxy in the relatively recent past. The shells are similar to ripples forming in a pond when a stone is tossed in. They sparkle with stars that were swept up from the encounter.The interaction may be providing enough fuel to power the quasar, which dominates the galaxy's centre. This observation supports the idea that quasars are born from mergers between galaxies.

The images were taken June 28 and July 4, 2005 with Hubble's Advanced Camera for Surveys.

The observation team consists of Gabriela Canalizo and Nicola Bennert of the University of California, Riverside; Bruno Jungwiert of the University of California, Riverside and the Academy of Sciences of the Czech Republic, Prague; Alan Stockton of the University of Hawaii, Honolulu; Francois Schweizer of the Carnegie Observatories, Pasadena; Mark Lacy of the California Institute of Technology, Pasadena; and Chien Peng of the Space Telescope Science Institute, Baltimore.

Credit: NASA, ESA, and G. Canalizo (University of California, Riverside)