In Search of Dark Asteroids

Ninjas knew how to be stealthy: Be dark. Emit very little light. Move in the shadows between bright places. In modern warfare, though, ninjas would be sitting ducks. Their black clothes may be hard to see at night with the naked eye, but their warm bodies would be clearly visible to a soldier wearing infrared goggles.

To hunt for the ninjas of the cosmos dim objects that lurk in the vast dark spaces between planets and stars, scientists are building by far the most sensitive set of wide-angle infrared goggles ever, a space telescope called the Widefield Infrared Survey Explorer (WISE).

WISE will scan the entire sky at infrared wavelengths, creating the most comprehensive catalog yet of dark and dim objects in the cosmos: vast dust clouds, brown dwarf stars, asteroids — even large, nearby asteroids that might pose a threat to Earth.

Surveys of nearby asteroids based on visible-light telescopes could be skewed toward asteroids with more-reflective surfaces. If there's a significant population of asteroids nearby that are very dark, they will have been missed by these previous surveys, says Edward Wright, principal investigator for WISE and a physicist at the University of California in Los Angeles.

The full-sky infrared map produced by WISE will reveal even these darker asteroids, mapping the locations and sizes of roughly 200,000 asteroids and giving scientists a clearer idea of how many large and potentially dangerous asteroids are nearby. WISE will also help answer questions about the formation of stars and the evolution and structure of galaxies, including our own Milky Way.