by Sarah Scoles
NASA's Fermi telescope is interested in, and sensitive to, the universe at its most energetic wavelengths: gamma rays.
Luckily for us and our DNA, gamma rays don't make it through the Earth's atmosphere. To study this high-energy, tiny-wavelength radiation, astronomers must launch telescopes into space, and counting photons as they smash into a detector.
Fermi was launched in 2008, a time at which we knew little (or at least much less) about the abundance and causes of gamma radiation.
Since then, Fermi has released an all-sky map of the gamma rays that have been detected. It looks like this:
That bright line is the plane of our own galaxy. You can think of this picture like a globe stretched out and printed in a textbook, with the equator going across the middle.
Because of Fermi, we know of 500 different sources of this high-energy radiation, and thus must be fairly extreme objects. Some--like pulsars--are within our own galaxy, but others are distant--like the blazars associated with active galaxies.
However, just because we can tell that gamma rays are coming from some spot in space does not mean we know what they're coming from, or the how of the what's high-energy emissions. One-third of the 500 gamma-ray sources remain a mystery. That's 166.67 mysteries! Science has a lot of work to do, and a strange remainder to figure out.
If you want to learn more, try this ScienceCast video
or visit the Fermi website.
By the way, I learned about this newest all-sky map from Deborah Byrd's EarthSky.org
post, which included a pretty amazing picture of the Fermi bubbles. These blurp up from the galactic center and go 20,000 light-years both above and below the equator I mentioned above. They and their absurd energy are thought to be the remnants of a cataclysmic event involving our hometown supermassive black hole. These sources of extreme gamma rays stretch across our sky all the time, but if it were not for some telescope floating miles above us, no one would ever see them.