14 DAY TRIAL // The Fermi Gamma-ray Space Telescope is, undoubtedly, the most sophisticated observatory of its class in orbit today. But this title was not obtained because someone decided to call it so, but because of the revolutionary knowledge about the Universe that it brought to the world. With its highly sensitive instruments, it was able to recently make two new finds – the fact that certain types of radio galaxies emitted gamma-rays, and emissions coming from an area of space just two light-years across, as in from a black hole and its immediate surroundings.
Building on observations made by the Compton Gamma-Ray Observatory, which managed to reveal that blazars and radio galaxies were two major sources of gamma-rays, and to find the first four soft gamma-ray repeaters, Fermi began to survey those targets in the galaxy that were out of CGRO's reach because of technical limitations. “Compton showed us that two classes of active galaxies emitted gamma rays – blazars and radio galaxies. With Fermi, we've found a third – and opened a new window in the field,” Italian National Institute for Astrophysics' Brera Observatory expert Luigi Foschini says.
Using Fermi's Large Area Telescope (LAT), the expert succeeded in inferring that the catchy-named galaxy PMN J0948+0022, a Seyfert 1 class, emitted gamma-rays, but found no evidence of a particle jet. Actually, the evidence pointed to the fact that no such jet existed, because the movement of gas in the galaxy was very slow. But the variable radio source at the galactic center seemed to tell another story.
“Unlike ninety percent of narrow-line Seyfert 1 galaxies, PMN J0948 also produces strong and variable radio emission. This suggested the galaxy was indeed producing such a jet,” Fermi LAT science group leader Gino Tosti adds. He works at the National Institute of Nuclear Physics, in Perugia, Italy, focusing mostly on active galaxies. “We are sifting through Fermi LAT data for gamma rays from more sources of this type. And we've begun a multiwavelength campaign to monitor PMN J0948 across the spectrum, from radio to gamma rays,” Foschini adds.
In another find, while surveying the galaxy NGC 1275 (Perseus cluster, 225 million light-years away), Fermi discovered that the source of gamma-rays was only two light-years in diameter, which seems to indicate that the emissions came directly from a black hole. “The gamma rays in NGC 1275 must arise from a source no more than two light-years across. That means we're seeing radiation from the heart of the galaxy – near its black hole – as opposed to emission by hot gas throughout the cluster,” Goddard Space Flight Center expert Teddy Cheung shares.