The other day we dropped in on the doomed German ROSAT telescope, which is still slowly grinding its way through the upper atmosphere en route to nemesis. Scientists used the orbiting observatory in the 1990s to study high energy sources like colliding galaxies and black holes. Best predictions at the moment call for it to re-enter and burn up in the atmosphere October 23 early Sunday morning Central time. It’s still too early to say exactly when and where.
If sitting in the dentist chair while getting your teeth X-rayed makes you wonder just what’s going on in your mouth, you’ll be happy to know the electromagnetic spectrum, which includes light, UV and radio waves, doesn’t end there. No, no, no. The most energetic form of light is gamma radiation or simply gamma rays. While too much X-ray exposure can lead to sickness, gamma rays are off the charts. They’re spawned in extremely explosive events like H-bombs or when matter screams down the maw of a black hole. Don’t get too close. Gamma rays are so powerful they’ll literally tear into your cell membranes and rip apart your DNA.
OK, enough of the scary stuff. A gamma ray telescope is clearly the tool of choice for scientists who want to learn more about what powers the most energetic and catastrophic happenings in the universe. Fortunately for all of life, except maybe the toughest bacteria, gamma rays are blocked by Earth’s atmosphere. NASA, with the help of other countries, built and launched the Fermi Gamma Ray Space Telescope into low-Earth orbit 2008 to surmount this little problem.
In its second survey of the sky, Fermi found 1873 gamma ray emitting objects or sources. The majority are giant black holes in the centers of galaxies that beam radiation into space as they gobble up gas and stars that stray too close. Others are superdense stars the size of cities called neutron stars that beam gamma rays into space as they spin like whirling dervishes. Neutron stars are created when a once-giant star collapses and explodes in a supernova explosion leaving only its tiny, dense core.
600 of Fermi’s finds however are complete mysteries. Some could be radiation shot off from colliding galaxies, but intriguingly, the sources might also be the sign of dark matter. Some scientists believe when two dark matter antiparticles bump into each other, they annihilate in a flash of gamma ray energy.
Antiparticles look and behave like normal electrons, protons and neutrons found in the atom but they have an opposite electric charge. Electrons are negatively charged, but an anti-electron, better known as a positron, is in every way its twin but positively charged. These strange siblings are as real as the hair on your head (if you still have hair). Put a particle and an antiparticle together and they’ll annihilate instantly in a burst of energy. If I’m not mistaken, this was the technology that powered the engines of the fictional star ship Enterprise in the Star Trek TV series.
The video, just released by NASA, explains the Fermi results and delves a bit more deeply into the puzzle of the gamma ray unknowns. I hope you’ll enjoy watching it. Whatever the new sources ultimately prove to be, scientists are certain to take the bait, opening a niche of new knowledge in the process.