Richard Massey

Astronomers used the infrared telescope and the old Hubble to discover a gaping void in the center of a galaxy in the Abell 402 cluster, as if an invisible tugboat had pulled billions of stars out of there. The missing mass equals two billion suns: it's not a cloud but a real lack of stars.

A magnifying glass focuses sunlight into a bright point. If the glass has a tiny flaw, the spot of light becomes distorted. Gravitational lensing works in a similar way: a massive galaxy bends light rays from a more distant source, creating an enlarged and sometimes distorted image.