WISE Mosaic of Cassiopeia

This mosaic of images from the Wide-Field Infrared Survey Explorer, or WISE, in the constellation of Cassiopeia contains a large star-forming nebula within the Milky Way Galaxy, called IC 1805 or the Heart Nebula, a portion of which is seen at the right of the image. IC 1805 is more than 6,000 light-years from Earth. Also visible are two nearby galaxies, Maffei 1 and Maffei 2. In visible light these galaxies are hidden by dust in IC 1805 and were unknown until 1968, when Paolo Maffei found them using infrared observations. Both galaxies contain billions of stars and are located some 10 million light-years away. Maffei 1 (the bluish elliptical object in the center of the image) has a disk-like structure and a central bulge; Maffei 2 (to the upper left of Maffei 1) is a spiral galaxy, also disk shaped, but with two prominent dusty spiral arms. Because this is an image of invisible infrared light, blue is mapped to the WISE 3.4 & 4.6 micron channels and is dominated by starlight. Green represents the WISE 12 micron channel, and red is the 22 micron channel, which are dominated by infrared radiation from warm interstellar dust.