No, not the poltergeists, although astronomers can’t say for sure what exactly fast radio bursts really are. But one thing they know as of this week is that they’re here in our Milky Way galaxy and astronomers can pinpoint exactly what is emitting them. Will this solve the baffling mystery of these brief blasts?
"If the same signal came from a nearby galaxy, like one of the nearby typical FRB galaxies, it would look like an FRB to us. Something like this has never been seen before."
That “this changes everything” observation comes from astronomer Shrinivas Kulkarni of Caltech – someone who knows a bit about fast radio bursts as a member of the STARE2 (Survey for Transient Astronomical Radio Emission 2) team whose purpose is to search the universe for these mysterious and extremely short radio signals. He described to ScienceAlert what happened on April 27 and 28 of this year.
On the 27th, multiple space observatories (the Swift Burst Alert Telescope, the AGILE satellite and the NICER ISS payload) picked up activity on SGR 1935+2154 – an ancient Milky Way stellar remnant with a small size but a high density. SGR 1935+2154 is identified as a ‘soft gamma repeater’ because it emits large bursts of gamma-rays and X-rays at irregular intervals. This is not unusual – there are other soft gamma repeaters.
“It was so bright that we saw it from the corner of our eyes, so to speak.”
On the 28th, everything changed, as astronomer Shriharsh Tendulkar at McGill University tells Gizmodo. A burst of radio waves hit the CHIME/FRB (Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project) radio telescope that was not looking directly at SGR 1935+2154 yet couldn’t miss what happened. The discovery was posted on the Astronomer’s Telegram – social media for astronomers – and confirmed by the STARE2 team, which also picked up something else.
“But we also saw something else we've never seen in an extragalactic FRB, and that's the X-ray counterpart. These are quite common in magnetar outbursts, of course. In fact, it is far more normal for magnetars to emit X-ray and gamma radiation than radio waves.”
That was the ‘A-ha!’ and ‘They’re he-ere!’ moment all wrapped into one for Kulkarni. It meant that magnetars -- neutron stars believed to have an extremely powerful magnetic fields – and Fast Radio Bursts are directly connected and the likely source of them around the universe. Unfortunately, you know what this means.
I’m not saying it’s not aliens … but it’s not aliens.
OK, the FRB from SGR 1935+2154 is not aliens, and that’s likely the case of similar FRBs. ScienceAlert points out that other FRBs behave differently and unpredictably, so this discovery doesn’t apply to all … leaving the door open for alternative causes.
Needless to say, astronomers will continue to search the skies for FRBs -- now with one more important tool in their bag.