... PG 1115+080: A Gravitational Cloverleaf . ... Credit: CISCO , Subaru 8.3-m Telescope , NAOJ Explanation: All four blue images in the above photograph are the same object. The gravitational lens effect of the red, foreground, elliptical galaxy visible near image center creates a cloverleaf image of the single distant quasar . Light from the quasar is pulled around the massive galaxy in different paths, corresponding to different images. ... Publications with words: gravitational lens - quasar . ...

... 2001 June 14 . Around The Arches Cluster . Credit: X-ray; NASA / CXC / Northwestern / F. Zadeh et al., IR; NASA/ HST /NICMOS, . ... Explanation: The most compact cluster of stars known in our galaxy, the Arches cluster , boasts 100 or so massive, young stars contained within a diameter of one light-year. ... Astronomers consider the tightly packed and relatively nearby Arches cluster, an analog of the furious star forming regions in galaxies millions of light-years away. ... About APOD | ...

... 2000, ApJ, 537, L49 . ... F. Palla . Invited Talk at the IAU Symposium 200 "The formation of binary stars" eds. R.D. Mathieu and H. Zinnecker (ASP Conf. Ser.) in press . Optical follow-up of ROSAT discovered candidate members of the open cluster Coma Berenices . ... 2000, A , in press . ... 2000, ApJ, in press . ... 2000, ApJ, in press (Sept. ... 2000, ApJ Lett., in press . ... Click to examine publications from other years . ... Star Formation Group . ... Arcetri Home Page . ...

... In one situation, we can use light from quasars to probe the material between us and them because that light may pass through one or more galaxies or gas clouds on its way to us. The gas inside the galaxies or the intergalactic clouds acts then as a filter, absorbing selected wavelengths from the quasar light. ... Light from a quasar must pass through clouds of gas and even faint galaxies -- each leaving its imprint on the light -- before we receive it here on Earth. ... Gravitational lensing . ...

Program number . ... Infrared Snapshots of 3CR Radio Galaxies . Abstract . ... Holland Ford, The Johns Hopkins University . ... An ACS H-alpha Survey of the Carina Nebula . ... A Snapshot Survey of the most massive clusters of galaxies . ... An ACS Imaging Survey of the Galaxies Hosting Strong Mg II Absorption . ... ACS observations of the galaxies in a giant Ly-alpha nebula at z~2.7 . ... An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe . ... Past weeks: . ...