NASA's WISE satellite spots a new, big comet
A NASA satellite launched in December to scan the universe for objects near and far is proving its worth, turning up objects in the inner solar system. Over the course of its 10-month mission, the Wide-field Infrared Survey Explorer (WISE) spacecraft will survey the skies in the infrared, a wavelength band optimal for spying on distant, dust-shrouded galaxies and for spotting nearby objects that are cool and dim, such as comets and failed stars known as brown dwarfs. (Even cool objects give off heat, which is visible in the infrared.)
On January 22, just 10 days after discovering its first near-Earth asteroid, WISE picked out a previously unknown comet streaking through the solar system. The thermal emission from the comet is visible above as a red blob in the center of the image.
The icy two-kilometer-wide comet, officially designated P/2010 B2 (WISE), orbits the sun in an elongated ellipse that takes 4.69 years to complete. The comet does not come especially close to Earth—it is currently passing through Mars's orbit and never comes within about 90 million kilometers of us—but WISE is expected to find near-Earth objects whose orbits are more worrisome. Its survey will help characterize the danger posed by near-Earth asteroids and comets. More dedicated instruments will be needed to fully catalogue the wayward objects in Earth's vicinity.