NASA’s Wide-field Infrared Survey Explorer – WISE – has recently finished a survey of small bodies in our solar system. The survey mission, called NEOWISE (for Near Earth Objects), used WISE’s infrared-imaging capabilities to identify 20 new comets and more than 33,000 main-belt asteroids. WISE also spotted 134 near-Earth objects – asteroids or comets that come within 28 million miles of Earth’s orbit.
Launched in December of 2009, WISE has already completed its original mission of infrared-mapping the sky, capturing images of objects and structures too faint to be seen in visible light but made evident by their heat emissions. After running out of the coolant needed to perform its first mission (in order to catch the faintest heat signals from deep space, the spacecraft itself had to stay very cold so as to not corrupt its own viewing!) WISE turned its remaining cameras to scanning for closer objects in our own solar system.
Although relatively much closer than distant stars and galaxies, asteroids and comets can be difficult to image because they are small and often visibly dark until they either come closer to the Sun or turn the right way to reflect sunlight. Infrared imaging helps locate dark objects better than visible-light imaging, since dark objects absorb more heat than bright ones. It’s also easier for scientists to estimate the sizes of asteroids with infrared data, since they’re looking at the entire object and not just the part that is reflecting sunlight.
Above is an infrared WISE image of the Tadpole nebula, a star-forming region in our galaxy 12,000 light-years away. Using multiple frames to make this image, WISE spotted two asteroids crossing its field of view, one near the center of the nebula and the other in the upper left. They each appear as a line of bright dots in the final image. (Actually the center asteroid had already been discovered in 1950, it is a 12-mile-wide main belt asteroid named 1719 Jens.)
The WISE mission has allowed scientists to see distant, dim objects that would never have been visible otherwise, as well as improve our knowledge of objects close by in our solar system . Since its start WISE has captured over 2.7 million images. Now it’s up to scientists to go through all that data…a job I’m sure any astronomer would love to have!
“WISE has unearthed a mother lode of amazing sources, and we’re having a great time figuring out their nature.”
– Edward Wright, P.I. of WISE at UCLA
Image: NASA/JPL-Caltech/WISE Team