Between this past Christmas and New Year’s Day, Brian Metzger realized he had his home to himself—no emails coming in, no classes to teach—and maybe, just maybe, the glimmer of an answer to one of astronomy’s most stubborn mysteries.
He chased hard after the lead, worried a little error could unravel everything or that someone else would put together the same pieces first. “You’re racing a little bit against the clock, because other people probably see this as well,” said Metzger, an astrophysicist at Columbia University. “It can kind of become all-consuming.”
Along with scores of other researchers around the world, Metzger has spent the last few years brainstorming ways to understand fast radio bursts (FRBs). These are millisecond-long blips of intense and unexplained radio signals that pop up all over the sky, temporarily outshining radio pulsars in our galaxy despite being
perhaps a million times farther away. Before 2013, many astrophysicists doubted that they even existed. In the years since, researchers have invented dozens of possible explanations for what might be causing them. One catalog counts 48 separate theories, a tally that until recently outnumbered the events themselves.
An FRB theory needs two parts, roughly akin to a suspect and a weapon in a cosmic game of Clue. The suspect is an astrophysical beast that can unleash vast sums of energy. The weapon is something that will transform that energy into a bright, head-scratchingly unusual radio signal.
Now Metzger and his colleagues think they have reconstructed the crime scene. Earlier this month they released a paper on the scientific preprint site arxiv.org that sketched out a way for FRBs to arise from explosions in regions of space cluttered with dense clouds of particles and magnetic fields.
The model favors, but doesn’t require, a magnetar as the source of the explosions. A magnetar is a young neutron star that sometimes burps out charged particles in a supersize version of the coronal mass ejections that erupt on the sun. Each new blast plows into the surrounding clutter. When it does, it creates a shock wave, which in turn beams a short, laserlike flash of radio waves halfway across the universe.
“In just very general terms, this makes a ton of sense,” said James Cordes, an astrophysicist at Cornell University, adding that while further details still need to be worked out, “I would say it’s a good horse to bet on.”
What the astronomers really like, though, is that Metzger’s theory generates very specific predictions for what future FRBs should look like, predictions that will soon be put to make-or-break tests. A new Canadian radio telescope called CHIME is expected to find between one and 10 FRBs each day after it becomes fully operational later this year. During initial testing last summer it detected a baker’s dozen of the bursts, results that were published in January. “I think that over the next year or so we’ll be able to test this very well,” said Shriharsh Tendulkar, an astrophysicist at McGill University and a member of CHIME’s FRB team.