G279.0+1.1 is a supernova remnant ( SNR ) with poorly known parameters , first detected as a dim radio source and classified as an evolved system . An analysis of data from the Fermi -LAT revealing for the first time an extended source of gamma rays in the region is presented . The diameter of the GeV region found is \sim 2.8 \degr , larger than the latest estimate of the SNR size from radio data . The gamma-ray emission covers most of the known shell and extends further to the north and east of the bulk of the radio emission . The photon spectrum in the 0.5–500 GeV range can be described by a simple power law , \frac { dN } { dE } \propto E ^ { - \Gamma } , with a spectral index of \Gamma = 1.86 \pm 0.03 _ { stat } \pm 0.06 _ { sys } . In the leptonic scenario , a steep particle spectrum is required and a distance lower than the previously estimated value of 3 kpc is favored . The possibility that the high-energy emission results from electrons that already escaped the SNR is also investigated . A hadronic scenario for the gamma rays yields a particle spectral index of \sim 2.0 and no significant constraints on the distance . The production of gamma rays in old SNRs is discussed . More observations of this source are encouraged to probe the true extent of the shell and its age .