File:WISE Last Light.jpg

English: On the morning of February 1st, 2011, NASA’s Wide-field Infrared Survey Explorer, or WISE, took its last snapshot of the sky. This “last light” image is reminiscent of the “first light” image from WISE, taken only 13 months prior. WISE’s final picture shows thousands of stars in a patch of the Milky Way Galaxy, covering an area 3 times the size of the full Moon, in the constellation Perseus. In the upper left corner, a faint wispy cloud can be seen bending around a pulsating variable star called EV Persei. After its coolant ran out in October of 2010, WISE warmed up from -260 degrees to -200 degrees C. This image contains data from the two detectors largely unaffected by the warm-up: 3.4 and 4.6 microns (the 12 and 22 micron detectors are no longer useful at the warmer temperatures). The colour is representational: cyan (blue-green) shows light detected by the 3.4 micron channel of WISE, and red shows light seen by the 4.6 micron channel. This region of the sky had been observed by WISE previously in all four of its detectors as part of its primary survey, and it is hard to see any difference in the quality of the last-light images at 3.4 and 4.6 microns.