Filipović et al. present a re-discovery of G278.94+1.35 as possibly one of the largest known Galactic supernova remnants (SNRs) – that they name Diprotodon. While previously established as a Galactic SNR, Diprotodon is visible in new ASKAP EMU and MWA GLEAM radio continuum images at an angular size of 3.3×3.2 degrees², much larger than previously measured. At the previously suggested distance of 2.7 kpc, this implies a diameter of 157×152 pc, which would qualify Diprotodon as the largest known SNR. The team find that Diprotodon is most likely at a much closer distance of ∼1 kpc, implying its diameter is the still sizeable 58×56 pc. They also present a new Fermi-LAT data analysis that confirms the angular extent of the SNR in gamma-rays.  The image above shows the ASKAP radio-continuum intensity image of Diprotodon at 943 MHz. The green-dashed circle indicates the previously measured extent, while the yellow dashed ellipse indicates the new boundaries of Diprotodon’s radio emission.  The top right corner shows the scaled size of the Moon (0.5 degrees), while the top left corner shows the animal Diprotodon.

The Diprotodon is an extinct genus of Australian marsupial from the Pleistocene period, resembling a giant wombat.  The team chose this name for G278.94+1.35 to raise awareness of this extinct Australian animal and to raise awareness of the current extinction rate of several other species in Australia.  Diprotodon was the largest known marsupial, up to 3.4m long and 2m tall and weighing up to 3,500 kg. It became extinct at the end of the continent-wide extinction of megafauna approximately 46,000 years ago.  As G278.94+1.35 is potentially among the largest SNRs, it is fitting to liken it to this largest of wombats, Diprotodon.