"Gamma-ray emission from the Sagittarius dwarf spheroidal galaxy due to millisecond pulsars" - Crocker et al. (2022)

There is a nearby galaxy, currently being consumed by our own Milky Way, known as the Sagittarius dwarf spheroidal which is a target of NASA’s Fermi Gamma-Ray Space Telescope in the hopes of detecting a signal from the dark matter that must surround it still. The idea being that the dark matter will self-annhilate when it meets itself releasing high energy particles that ultimately decay to gamma-ray radiation.

So the scientific world was more than a little excited to see such radiation from this object, but is it caused by the dark matter? Extraordinary claims require extraordinary evidence - and after all one must rule out all the explanations before what remains, however extraordinary, can be assumed to be the case. Well one thing we do know that exists are spinning dead cores of stars (seriously how cool is that sentence?) known as millisecond pulars that emitting a lot of high energy radiation.

This work led by the ANU’s Dr Roland Crocker and an absolutely gigantic list of the best and brightest in astronomy - with my student Thomas Venville proudly holding his head high amongst such giants - explored all the evidence we had from Fermi and found that sadly the signal from these pulsars can reasonably explain this… there is a hint of more but at this stage, we must be conservative and presume that this is the case for other such signals in more distant galaxies too. The search for the dark matter signal continues!