Hubble tracks down a galaxy cluster's dark matter

Hubble zooms on the sky: 1. Sky map showing the stars as seen by the naked eye (data from ESA 's Hippacos satellite) 2. 2.5 degree image from Digitized Sky Survey 2 3. Ground-based image of CL0024+1654 from the Canada-France-Hawaii Telescope (CFHT) using the CFHT12k camera 4. The 39 Hubble Space Telescope images (WFPC2 camera)