Since 2007, astronomers have detected curious bright blasts of radio waves from the cosmos, each lasting no more than a few milliseconds. Now scientists have been able to pinpoint the source of one of these pulses: a galaxy 1.9 billion parsecs (6 billion light years) away.
It probably came from two colliding neutron stars, says astronomer Evan Keane, a project scientist for the Square Kilometre Array (SKA). Keane, who works at the SKA Organization’s headquarters at Jodrell Bank Observatory outside Manchester, UK, led the team that reports the detection in Nature1.
The discovery is the “measurement the field has been waiting for”, says astronomer Kiyoshi Masui of the University of British Columbia in Vancouver, Canada. By finding more such fast radio bursts (FRBs) and measuring the distance to their source, astronomers hope to use the signals as beacons to shed light on the evolution of the Universe.
Eyes on the skies
All but one of the 16 previously reported FRBs were found long after the signals reached Earth, by trawling through archives of telescope data. But today, supercomputers can process these signals in real time and detect them as they arrive, says Keane.
On 18 April 2015, the Parkes radio telescope in Australia detected a burst lasting less than 1 millisecond, one of the shortest yet. Parkes’ resolution isn’t fine enough to pinpoint the location of signals, but Keane, who saw the news when he checked emails buzzing into his phone, alerted a network of higher-resolution ground- and space-based telescopes. Two hours after the initial burst, the Australia Telescope Compact Array in New South Wales caught what appeared to be a fading radio afterglow in the same area.
This narrowed the search field enough for the 8.2-metre Subaru Telescope on Mauna Kea, Hawaii, to home in on a lone elliptical galaxy, which Keane and his team say is almost certainly the source of the burst.
The galaxy is relatively old, and so makes new stars very rarely. Because of that, Keane’s team thinks that the burst came from two colliding neutron stars, which orbited each other in a death spiral until they merged. The brevity of the burst is consistent with the expected timescale for such an event, rather than a collision between larger objects such as white dwarves, or a massive supernova. (If the event was a neutron-star merger, it would also have emitted gravitational waves — the ripples in space-time that the US Laser Interferometer Gravitational-Wave Observatory reported detecting two weeks ago.)
Not all FRBs fit the scenario for a neutron-star collision. Last December2, Masui and his colleagues reported a detection by the Green Bank Telescope in West Virginia that seems to originate from a young neutron star with a strong magnetic field emitting intense flares. This suggests that there are multiple kinds of bursts, from different origins. “The implications for the origins of FRBs are still a bit unclear,” says Victoria Kaspi, an astronomer at McGill University in Montreal, Canada.
SOURCE: Mark Zastrow