These ghostly swirls are the first images of gas clouds reflecting starlight. Lying more than 1,000 light years away, they are part of the Perseus Molecular Cloud, a region where new stars form. Usually, such clouds appear in astronomical images merely as dark regions where light from more distant stars is blocked. Thermal emission from the gas and dust can often be detected by radio telescopes, but directly reflected starlight — ‘cloudshine’ — is normally too dim to see.

Credit: J. FOSTER & A. GOODMAN/HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS

Jonathan Foster and Alyssa Goodman of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, captured these false-colour images of the Perseus complex using the new OMEGA 2000 camera at Calar Alto Observatory in southern Spain (J. B. Foster and A. A. Goodman Astrophys. J. Lett. 636, L105–L108; 2006). They say that scattered light alone can explain the images, and that the near-infrared cloudshine could even be used to probe the three-dimensional structure of molecular clouds.