An Australian-led team of international astronomers have determined source of a powerful, one-off burst of cosmic radio waves. They have pinpointed it to a massive galaxy billions of light years away, with properties that upend what scientists previously thought they knew about the formation of mysterious fast radio bursts (FRBs). "This result is highly anticipated within the astronomy community," Casey Law, an astronomer at UC Berkeley who was not involved in the study told AFP.
The findings, published in the journal Science, are among the most significant since the discovery in 2007 of FRBs, which flash for only a micro-instant but can emit as much energy in a millisecond as the Sun does in 10,000 years.
In 2017, astronomers were able to trace the source of a repeating burst, but locating a one-off FRB presented a much more difficult challenge.
Without the benefit of knowing where to look, a team led by Keith Bannister of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) had to devise a new methodology.
"You can think of it as live action replay mode, where we have a computer that's actually looking for the FRB, so it looked through about a billion measurements every second and I tried to find the one that contains an FRB," Bannister told AFP.
Bannister and his team pinpointed the location of FRB 180924 about 3.6 billion light years from Earth.
The discovery was detected on CSIRO's Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in Western Australia.
ASKAP has 36 dish antennas, with the burst reaching each one at a slightly different time, allowing the scientists to calculate its origin.
"It's like looking at the Earth from the Moon and not only knowing what house a person lived in, but what chair they were sitting in at the dining room table," Bannister said.
The team then imaged the galaxy with the European Southern Observatory's Very Large Telescope in Chile, and measured its distance with the Keck telescope in Hawaii and the Gemini South telescope in Chile.
While the previously localized FRB 121102 was found to emanate from a dwarf galaxy that was actively forming young stars, the new FRB comes from the outskirts of a massive galaxy with old stars, suggesting a completely different engine is responsible for its creation.
"The first localization inspired lots of modeling based on magnetars formed in the deaths of massive stars," said Law, a model which predicted a number of properties confirmed in 121102.
A magnetar is a highly-magnetized type of neutron star, which are formed by the gravitational collapse of a star not quite massive enough to produce a black hole when it explodes.
But the new location is incompatible with the old theory, suggesting there are multiple channels for forming FRBs.
"This might suggest that repeating and non-repeating FRBs come from completely different origins," said Shriharsh Tendulkar, an astronomer at McGill University who was not involved in the work.