They are named fast radio
bursts, or FRBs, and these odd, brief signals from space are covered in
mystery. But thanks to Canada's biggest radio telescope, astronomers are finding
more of them in their hunt to know what makes these objects tick.
The first FRB was found in
2007 by an astronomer and his apprentice while studying 2001 data gathered from
the Parkes Observatory in New South Wales, Australia. Since then, many more
have been discovered. As to what is producing these signals, researchers have
yet to learn. But these momentary signals that are journeying the cosmos —
and last only a millisecond or so — had another surprise: some of them
repeated.
The first of these repeating
FRBs were found by McGill PhD student Paul Scholz in 2015. A second one was detected
last January. And the list is getting lengthier. In a recent study, submitted
to the Astrophysical Journal Letters and pre-printed on
arXiv.org, a group of Canadian researchers disclose that the Canadian
Hydrogen Intensity Mapping Experiment (CHIME) telescope discovered eight
more repeating FRBs. The discoveries are a significant step in better
understanding what is generating these powerful signals and where precisely
they are coming from.
“The first biggest
conclusion [from the paper] is that this is not an anomalous phenomenon. This
is for real,” said Victoria Kaspi, an astronomer at McGill University and the
Canadian Institute for Advanced Research (CIFAR). “It just takes time and patience
to find them. And two, it offers the opportunity to localize them, and that's
huge in the FRB field.”
The CHIME apparatus
cannot be both sensitive and accurate in its discoveries, which means it can’t pinpoint
the signal. In its place, its job is to detect as many as
it can. Finding their precise position is up to other
telescopes.
“Discovering eight sources
like this is so important because it says we have a lot more repeating
FRBs and can figure out the environments and the galaxies these FRBs are
located in if we follow them up with other telescopes,” said Pragya
Chawla, co-author of the paper and a PhD student at the McGill Space Institute.
Of the 10 reocurring FRBs,
only two have been traced back to their location of birth: one is in a
dwarf galaxy and the other, in a spiral galaxy. FRBs are a hot topic
in the astronomical world, mostly because they're a fairly new discovery and
the mechanism responsible isn't understood.
"We think we understand
what's in the cosmos," Kaspi said. "But fast radio bursts were a
total surprise. Nobody expected them. Nobody predicted them. Really, it was
technological advancements that allowed us to see this. And I think it's really
interesting that we're still learning very basic things about what's going on
in the universe."
Since they produce such
intense energy, some theories propose that the source is a neutron star, a
small dense star left over after a supernova. Another theory proposes it could
be a magnetar, a star like a neutron star, but with an exceptionally powerful
magnetic field. Although the known FRBs — both the repeaters and apparent
non-repeaters — are thought to initiate in other galaxies, one of the newly discovered
ones appears to be nearer than the others, maybe even within the Milky Way. Though,
Chawla said that if it were to be detected within Milky Way that “it would
be very astounding”.
“Because we know a lot of
neutron stars within our own galaxy that emit such pulses, but none of them
have been seen to be found that far at the edge of our galaxy.”
CHIME has been quite effective
in its hunt for these mystifying objects, but the even better news is that the
telescope is not running on full power: there is still the need to better
calibrate it. Once that is done, it's expected that even more FRBs will be discovered
on a daily basis. And that means more data to deliver other astronomers with
the apparatuses of unravelling their mystery.
“I think the upcoming year
will be a really good one for FRBs,” Kaspi said. “Are we going to know the
answer in a year's time? I don't know. I don't know. Maybe. But I think we will
have made significant progress in a year.”
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