NASA's Spitzer Space Telescope launched into space in August 2003. For the 16th anniversary of this event (yeah, I know, I'm a bit late; I've been busy) they released a "something old, something new" image of the spiral galaxy M81, a classic grand-design spiral galaxy located just 12 million light years away in the constellation of Ursa Major. It's close enough and big enough that it an be spotted from dark skies easily with binocs (I've heard tales, probably true, that it's been seen naked eye!), so when you launch a telescope into space and point it toward M81, what you get is pure magnificence:
The nearby spiral galaxy M81 seen in three infrared colors by the Spitzer Space Telescope. Credit: NASA/JPL-Caltech
Spitzer doesn't see visible light, the kind our eyes see. Instead it sees in the infrared, light with wavelengths longer than our eye's capability to detect. This is a three-color image: what you see as blue is actually infrared light at a wavelength 3.6 microns (about 5 times longer than what our eyes can see), green is 4.5 microns, and red 8 microns. These three different IR colors tell us three different stories about the galaxy.
The center ...