WISE

This animation illustrates the benefits of observing asteroids in infrared light. It begins by showing two artistic interpretations of asteroids up close. They are about the same size but the one on the right is darker. The animation zooms away to show how a visible-light telescope would see these two space rocks, located at the same distance millions of miles away from Earth, against a background of more distant stars. The one on the left would be much easier to see because it reflects more visible light from the sun.

The animation then transitions to an infrared view of the same two objects. Both asteroids are equally as bright because the telescope is picking up infrared light coming from the bodies themselves, as a result of being heated by the sun. The measurements are not strongly affected by how light or dark an asteroid is, a property called albedo. Instead, the brightness is more directly related to an asteroid's size. Therefore, infrared telescopes like WISE are better at both finding the small, dark asteroids and determining asteroid sizes.

Image credit: NASA/JPL-Caltech