Attack of the Gamma-Ray Spiders from Space!


  • The Fermi Gamma-ray Space Telescope has been surveying the sky in the gamma-ray band (photon energies of 100 MeV and greater) since August 2008. The Large Area Telescope, Fermi's prime instrument, has revealed a large population of gamma-ray sources associated with active galactic nuclei, pulsars, and a few other source classes. However, about a third of the gamma-ray sources are unassociated with any known gamma-ray emitting source. I will describe a worldwide effort to search for pulsars powering these sources. We have been extremely successful, discovering 56 new millisecond pulsars (MSPs), over 1/4 of all known MSPs in the Galaxy! A striking feature of these new MSPs is that many of them are so-called `black widow' systems that are eating away their companion with powerful beams of particles and high energy radiation. Another class being found are the `redbacks', named after the Australian cousin of the black widow spider. These systems are proving to be the missing link between accreting X-ray binaries and millisecond pulsars. I will describe the Fermi mission, our radio searches and some of the surprising systems we have discovered. This work is supported by the Fermi Guest Observer Program administered by NASA.