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EI2GYB > ASTRO 01.09.21 10:37l 132 Lines 7248 Bytes #999 (0) @ WW
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Subj: CHIME telescope detects more than 500 mysterious fast radio
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Sent: 210901/0834Z 13967@EI2GYB.DGL.IRL.EURO BPQ6.0.22
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CHIME telescope detects more than 500 mysterious fast radio bursts in its
first year of operation.
The large radio telescope CHIME has detected more than 500 mysterious fast
radio bursts in its first year of operation, MIT researchers report.
The observations quadruple the number of known radio bursts and reveal
two types of FRBs: one-offs and repeaters.
To catch sight of a fast radio burst is to be extremely lucky in where and
when you point your radio dish.
Fast radio bursts, or FRBs, are oddly bright flashes of light, registering
in the radio band of the electromagnetic spectrum, that blaze for a
few milliseconds before vanishing without a trace.
These brief and mysterious beacons have been spotted in various and
distant parts of the universe, as well as in our own galaxy.
Their origins are unknown, and their appearance is unpredictable.
Since the first was discovered in 2007, radio astronomers have only
caught sight of around 140 bursts in their scopes.
Now, a large stationary radio telescope in British Columbia has nearly
quadrupled the number of fast radio bursts discovered to date.
The telescope, known as CHIME, for the Canadian Hydrogen Intensity
Mapping Experiment, has detected 535 new fast radio bursts during its first
year of operation, between 2018 and 2019.
Scientists with the CHIME Collaboration, including researchers at MIT, have
assembled the new signals in the telescope's first FRB catalog, which they
will present this week at the American Astronomical Society Meeting.
The new catalog significantly expands the current library of known FRBs,
and is already yielding clues as to their properties. For instance, the
newly discovered bursts appear to fall in two distinct classes: those that
repeat, and those that don't.
Scientists identified 18 FRB sources that burst repeatedly, while the rest
appear to be one-offs.
The repeaters also look different, with each burst lasting slightly longer
and emitting more focused radio frequencies than bursts from single,
nonrepeating FRBs.
These observations strongly suggest that repeaters and one-offs arise
from separate mechanisms and astrophysical sources.
With more observations, astronomers hope soon to pin down the extreme
origins of these curiously bright signals.
"Before CHIME, there were less than 100 total discovered FRBs; now,
after one year of observation, we've discovered hundreds more," says
CHIME member Kaitlyn Shin, a graduate student in MIT's Department of Physics.
"With all these sources, we can really start getting a picture of what
FRBs look like as a whole, what astrophysics might be driving these events, and how they can be used to study the universe going forward."
Seeing flashes
==============
CHIME comprises four massive parabolic radio antennas, roughly the size
and shape of snowboarding half-pipes, located at the Dominion Radio
Astrophysical Observatory in British Columbia, Canada.
CHIME is a stationary array, with no moving parts.
The telescope receives radio signals each day from half of the sky as
the Earth rotates.
While most radio astronomy is done by swiveling a large dish to focus
light from different parts of the sky, CHIME stares, motionless, at the
sky, and focuses incoming signals using a correlator -- a powerful
digital signaling processor that can work through huge amounts of data,
at a rate of about 7 terabits per second, equivalent to a few percent
of the world's internet traffic.
"Digital signal processing is what makes CHIME able to reconstruct
and 'look' in thousands of directions simultaneously," says Kiyoshi Masui,
assistant professor of physics at MIT, who will lead the group's conference
presentation. "That's what helps us detect FRBs a thousand times more
often than a traditional telescope."
Over the first year of operation, CHIME detected 535 new fast radio bursts.
When the scientists mapped their locations, they found the bursts were evenly distributed in space, seeming to arise from any and all parts of the sky. From the FRBs that CHIME was able to detect, the scientists calculated that fast radio bursts, bright enough to be seen by a telescope like CHIME, occur at a rate of about 9,000 per day across the entire sky -- the most precise estimate of FRBs overall rate to date.
"That's kind of the beautiful thing about this field -- FRBs are really hard
to see, but they're not uncommon," says Masui, who is a member of MIT's
Kavli Institute for Astrophysics and Space Research.
"If your eyes could see radio flashes the way you can see camera flashes,
you would see them all the time if you just looked up."
Mapping the universe
====================
As radio waves travel across space, any interstellar gas, or plasma, along
the way can distort or disperse the wave's properties and trajectory.
The degree to which a radio wave is dispersed can give clues to how much
gas it passed through, and possibly how much distance it has traveled from
its source.
For each of the 535 FRBs that CHIME detected, Masui and his colleagues
measured its dispersion, and found that most bursts likely originated
from far-off sources within distant galaxies.
The fact that the bursts were bright enough to be detected by CHIME
suggests that they must have been produced by extremely energetic sources.
As the telescope detects more FRBs, scientists hope to pin down exactly
what kind of exotic phenomena could generate such ultrabright, ultrafast signals.
Scientists also plan to use the bursts, and their dispersion estimates, to
map the distribution of gas throughout the universe.
"Each FRB gives us some information of how far they've propagated and how
much gas they've propagated through," Shin says. "With large numbers of FRBs,
we can hopefully figure out how gas and matter are distributed on very large
scales in the universe.
So, alongside the mystery of what FRBs are themselves, there's also the
exciting potential for FRBs as powerful cosmological probes in the future."
This research was supported by various institutions including the Canada
Foundation for Innovation, the Dunlap Institute for Astronomy and
Astrophysics at the University of Toronto, the Canadian Institute for
Advanced Research, McGill University and the McGill Space Institute via
the Trottier Family Family Foundation, and the University of British Columbia.
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