This artist's conception shows simulated data predicting the hundreds of failed stars, or brown dwarfs, that NASA's Wide-field Infrared Survey Explorer (WISE) is expected to add to the population of known stars in our solar neighborhood. Our sun and other known stars appear white, yellow or red. Predicted brown dwarfs are deep red.

The green pyramid represents the volume surveyed by NASA's Spitzer Space Telescope -- an infrared telescope designed to focus on targeted areas in depth, rather than to scan the whole sky as WISE is doing. Spitzer found 14 of the coolest known brown dwarfs in this region, which is one-fourtieth the volume that WISE is combing. Astronomers think WISE will find hundreds of these cool orbs within 25 light-years from the sun (a region marked by the blue sphere).