In the first year of its five-year mission, NASA’s Fermi Gamma-ray Space Telescope discovered over 1,000 places that stream high-energy gamma-rays.
Peter Michelson: We’re looking at the universe with a different set of eyes than we’re born with.
Astrophysicist Peter Michelson of Stanford is principal investigator of the Large Area Telescope on the Fermi Telescope. High energy hot spots in the universe are revealed with gamma-rays, said Michelson. Gamma rays are a little like x-rays.
Peter Michelson: These are the highest energy form of radiation produced in nature. Looking at the universe with gamma-ray eyes, this reveals places in the universe where particles are accelerated to very high energies. And among those are many sources that have never been seen – things like pulsars, that are seen only in gamma-rays; gamma-ray bursts, that are explosions that we see expanding at close to the speed of light.
Michelson said the Fermi telescope has also discovered many of what he calls “active galaxies” centered around a massive black hole. The gravity of a black hole is so strong that not even light can escape. Michelson added that the Fermi space telescope might help show, in greater detail than ever before, what the neighborhood surrounding a black hole looks like.
EarthSky asked Dr. Michelson what it is about gamma rays that is special in probing our universe.
Peter Michelson: There are a number of reasons. The principal one is that the gamma rays are produced by particles that are accelerated to enormously high energies. And they come directly from the regions where the particle acceleration occurs. And typically, x-rays and optical and infrared photons do not emerge from those regions. So gamma rays give us real insight into the dynamics of how, for example, a very massive black hole at the center of a distant galaxy can accelerate charged particles to enormous energies.
Gamma rays also might shed light on the nature of dark matter, says Michelson.
Peter Michelson: On another front, gamma rays may give us a window into the nature of dark matter. Dark matter is a mysterious form of matter that by its very name, we don’t see it optically. And there is a chance that we will be able to see it with gamma rays.
Dr. Michelson responded to whether the Fermi space telescope would actually “see” dark matter.
Peter Michelson: Well, we’re not sure that Fermi is seeing dark matter yet. But the way we would be able to see it, if theories are correct, and theories suggest that the dark matter particles could produce gamma rays either by annihilation – that is, one dark matter particle meets another dark matter particle and they turn into gamma rays and other kinds of particles. And we may be able to detect the gamma rays that come from that annihilation process.
Dr. Michelson spoke more about the findings so far from the Fermi space telescope.
Peter Michelson: Fermi’s had a great year in orbit. We’re about to release a catalog of high energy gamma ray sources that we’ve detected. There are more than a thousand entries. And among those are many sources that have never been seen before. Among the new sources are in fact things like pulsars, that are seen only in gamma rays, gamma ray bursts, that are explosions that we see expanding at close to the speed of light. And we’ve seen the most energetic gamma ray bursts ever seen.
Dr. Michelson spoke about what lies ahead for the next four or five years of the Fermi space telescope.
Peter Michelson: I think the mission will continue, at least for the next four or five years, and as we go forward, we’re going to look deeper and deeper into the universe, building up. It’s like a photographic plate. If you want to see something that’s very faint, you have to expose the photographic plate for a long time. So we will see more and more of our universe in high energy gamma rays as time goes on. And my fondest dream, in fact, is that eventually we’ll figure out the riddle of what dark matter is.