As a rule of thumb, if something is emitting gamma rays, you should stay away. Gamma rays are the most damaging type of radiation. They are the reason why nuclear waste is put into lead containers. And yet, astronomers are actively seeking these rays as they give us information about the most energetic events in the universe. Using the Fermi Space Telescope, scientists have released the most detailed map of the sky in gamma rays.
The map allowed astronomers to conduct a census of powerful events. The team mapped hundreds of sources as well as discovering 48 previously undetected objects.
"Of the 360 sources we cataloged, about 75 percent are blazars, which are distant galaxies sporting jets powered by supermassive black holes," co-investigator Alberto Domínguez at the Complutense University in Madrid said in a statement, where a high resolution version of the map is also available.
"The highest-energy sources, all located in our galaxy, are mostly remnants of supernova explosions and pulsar wind nebulae, places where rapidly rotating neutron stars accelerate particles to near the speed of light."
Astronomers were able to improve the observatory detecting abilities by studying how the detector has been responding to gamma rays since it was launched in 2008. "The end result is effectively a complete instrument upgrade without our ever having to leave the ground," said Marco Ajello, a Fermi team member at Clemson University in South Carolina.
Ground-based gamma ray detectors have only seen about one-quarter of the objects in the catalog so far, and they now have 280 new targets to observe in detail. A paper describing the catalog has been accepted for publication in The Astrophysical Journal Supplement.
A segment of the All-Sky map, which highlights a powerful unknown object. NASA/DOE/Fermi LAT Collaboration
There are 25 new extended sources in the catalog, including three new pulsar winds and two new supernova remnants. "Finding more of these objects enables us to probe their structures as well as better understand mechanisms that accelerate the subatomic particles that ultimately produce gamma-ray emission," Jamie Cohen, a University of Maryland graduate student working with the Fermi Team, added.
Among these extended sources, there’s a particularly bright one which NASA labels "unknown." The researchers say that it’s most likely of galactic origin, as extragalactic objects wouldn’t be as bright. It could be a pulsar, black hole, or a neutron star. Professor Ethan Siegel, writing for Forbes, suggest that the signal is associated with a nebula structure. More investigation on this and the other 47 objects is a very exciting development for the field of high-energy astrophysics.