One of the brown dwarfs, dubbed WISE 2, appears to be as cold as any that are known. It may even be colder, Wright said, than the brown dwarfs recently found by the UKIDSS survey, which are estimated to be in the neighborhood of 500 Kelvin, but the exact temperature of WISE 2 is uncertain (as are the temperatures of the UKIDSS objects). WISE 1 is a bit warmer, Wright said: “We think this is about an 800-Kelvin object.”
Brown dwarfs share characteristics with both stars and planets. Despite the success of surveys such as 2MASS and SDSS, they have been unable to find brown dwarfs cooler than 750 degrees Kelvin. Cooler objects primarily emit light at wavelengths longer than either of those surveys probe, and it is at these wavelengths where WISE will operate. With WISE we will be able to see 450-K brown dwarfs out to a distance of 75 light-years (ly), 300-K brown dwarfs out to 20 ly, and 150-K brown dwarfs out to 10 ly. Finding these cooler objects will provide examples of exoplanet-like atmospheres in order to investigate atmospheric properties in the unexplored temperatures between 150 and 750 Kelvin.
WISE will determine how common these objects are in our own Solar Neighborhood, allowing us to measure the efficiency of the star formation process at its lowest masses. WISE will also allow us to determine if star formation has a cut-off mass below which formation is inhibited. At the moment, we believe that brown dwarfs are as prevalent as stars. Because brown dwarfs are so common, it is likely that the closest “star” to the Sun is not Proxima Centauri but some hitherto undiscovered brown dwarf that will be imaged successfully for the first time by WISE.
The mission has observed more than 60,000 asteroids, both Main Belt and near-Earth objects. Most were known before, but more than 11,000 are new.