From Earth, the Pinwheel Galaxy looks to us like just a pinprick of light in the Big Dipper. But it's an enormous galaxy that's twice the size of our own. And in this new image of the galaxy from NASA, you can see that the Pinwheel is bursting with supernovae — the purple regions in this image highlight areas of extreme heat, where stars are exploding. What's interesting is that these gigantic explosions are happening both in the center and at the extreme edges of the galaxy's arms.
The red colors in the image show infrared light, as seen by the Spitzer Space Telescope. These areas show the heat emitted by dusty lanes in the galaxy, where stars are forming. The yellow component is visible light, observed by the Hubble Space Telescope. Most of this light comes from stars, and they trace the same spiral structure as the dust lanes seen in the infrared. The blue areas show ultraviolet light, given out by hot, young stars that formed about 1 million years ago. The Galaxy Evolution Explorer, which NASA recently loaned to the California Institute of Technology in Pasadena, Calif., captured this component of the image.
Last, the hottest areas are shown in purple, where the Chandra X-ray observatory observed the X-ray emission from exploded stars, million-degree gas and material colliding around black holes. The Pinwheel Galaxy is nearly twice the size of our Milky Way. The glowing lights indicate massive stars, black holes and supernova explosions, all wrapped in the hot gas "arms" of the galaxy.
The Pinwheel Galaxy is 21 million light years away. Read more about it, and the "supernova of a generation" spotted in the Pinwheel, on The Daily Galaxy.