One of the big mysteries in astronomy is unfolding right before our eyes: fast radio bursts.
And now a new Canadian radio telescope has come online, detecting many new bursts, including
the second ever seen repeating.
Finally, with the right tools at their disposal, astronomers are going to be able to get to
bottom of this puzzling mystery.
I did an introduction episode about fast radio bursts back in April 2017, which I talked
about this mystery, and suggested that Canada’s CHIME observatory would be the right tool
to deliver thousands more data points to astronomers.
Well, here we are, it’s almost two years later and CHIME is now operational here in
British Columbia.
Astronomers working with CHIME announced at the meeting of the American Astronomical Society
this week in Seattle that they had detected 13 new fast radio bursts with the instrument.
Most importantly, they found a signal that had repeated 6 times, giving astronomers a
consistent target to watch, and get some kind of hint about what could be producing these
bizarre signals.
First a quick backgrounder.
Fast radio bursts, or FRBs were first discovered by accident in 2007 when Duncan Lorimer and
his student David Narkevic were looking through archival data captured by the Parkes radio
dish in Australia.
They found a peculiar burst of radio emissions that had actually occurred back in 2001.
It was less than 5 milliseconds in duration near the Small Magellanic Cloud.
This was known as the Lorimer Burst.
Over the next decade many more bursts were detected, from radio telescopes around the
world, like the Green Bank Telescope and Arecibo.
The problem is that the bursts happen once, in a random place in the sky, and then they’re
almost never seen again.
Since radio telescopes are only scanning a specific part of the sky, the chance of finding
a burst had been very low.
Canadian astronomer Victoria Kaspi from McGill estimated that there could be as many as 10,000
of these fast radio bursts going off across the sky every day.
But you would need a very specific kind of instrument to be able to detect them.
Enter CHIME, or the Canadian Hydrogen Intensity Mapping Experiment, which was built in Penticton,
British Columbia.
Hey, I live in British Columbia.
Well, it’s actually about 8 hours and a ferry ride away, so maybe some future road
trip.
CHIME uses 4 100-meter cylindrical reflectors and 1024 dual-polarized antennas to rapidly
map out the entire sky in the 400-800 MHz radio spectrum.
Its primary purpose is to see regions of hydrogen gas across the observable Universe, to help
map out the expansion history of the Universe.
To help astronomers chart the history of dark matter and dark energy in the Universe.
Every day it builds a map of the entire northern hemisphere, moving from section to section
every 15 minutes.
This allows it to keep track of every single known pulsar in the Northern sky.
Which means that it’s perfectly positioned to also see fast radio bursts as they pop
off in the field of view.
Even as CHIME was under construction, it was starting to turn up fast radio bursts, but
astronomers weren’t able to fully map them out.
During its pre-commissioning run in the summer of 2018, CHIME turned up a total of 13 bursts,
even though it was running at a fraction of its full capacity.
Deborah Good, an astronomer working with the project predicted that CHIME will find more
than 1,000 more bursts this year.
Most of these bursts had some kind of scattering, which tells astronomers about the environment
that the source was in when it released the radio waves.
Some kind of dense area like a supernova remnant or the supermassive black hole at the heart
of a galaxy.
One of the most fascinating discoveries, however, was the discovery of a repeating burst.
It happened in a location that was well mapped out by the instrument: the celestial north
pole near Polaris.
Even during the commissioning period, it detected bursts coming 6 times from the same location.
This was the second time a repeating burst was ever seen.
Even more peculiar, there isn’t anything obvious in that part of the sky.
They estimated that it was generated by something about 1.6 billion light-years away, so more
detailed studies with telescopes like Hubble might be able to match up a galaxy with the
source of the burst.
CHIME also detected fast radio bursts at much longer wavelengths than anything that had
seen before, nearly a meter across.
Until this point, the big problem with fast radio burst was just the total lack of observations.
All of the bursts had been captured randomly, and there wasn’t any kind of comprehensive
surveys like we have in other fields.
So finally, CHIME demonstrates that astronomers will soon have data collected on thousands
of fast radio bursts.
Of course, the deep question is, what are they?
And right now, astronomers are mostly guessing.
I’ll list out the ideas so far, and then in a couple of years when the solution is
finally worked out, we can look back and laugh at these ridiculous suggestions
And I’ll get to that in a second, but first, I’d like to thank:
Naja Scheel Thomsen Edwin Smith
Graham Jordan Petr Smital
Stephen Boyle Rani B
Lindsay Buroker
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It’s been almost two years since my last video on fast radio bursts, so let’s take
a look at what astronomers think is causing them.
In their study, the authors noted a similarity between the properties of the fast radio bursts
and solar radio bursts.
After World War II, radio operators turned their dishes to the skies to search for signals,
and the most obvious target was the Sun.
Almost immediately they detected bursts of radio emissions coming from the Sun.
In general, they can buzz as radio noise for several hours, or have quick blasts that last
just a couple of minutes.
What causes them is still a bit unclear, but astronomers think they come from energetic
electrons trapped on coronal magnetic field lines.
As the lines snap and reconfigure, radio emissions are detectable.
This is an important field to study, since the strength of the solar wind, flares and
coronal mass ejections can impact us here on Earth.
What’s interesting is that these solar radio bursts can have similar frequencies to the
lowest fast radio bursts recently announced.
So, is there some kind of super version of solar radio bursts on massive stars?
One of the most extreme kinds of stars out there are magnetars.
These are neutron stars, what’s left over as a massive star explodes as a supernova.
All neutron stars have powerful magnetic fields, but magnetars rotate quickly, and can have
magnetic fields hundreds of millions of times more powerful than anything we can make here
on Earth.
As their field lines snap and connect, this could release an enormous amount of energy,
detectable in radio wavelengths.
In fact, astronomers estimate that these fast radio bursts contain 25 million times more
energy than the Sun, released in just a millisecond.
Another possibility is that fast radio bursts could be evidence of an exotic compact object
known as a “strange star”.
These would start out as neutron stars, but accrete more and more material onto their
surface, which eventually causes the crust to collapse down, becoming a more compact
strange star.
A huge amount of electron and positron pairs would be released, with large amounts of magnetic
energy.
Whatever is going on, something extreme must be generating them.
Of course, then you can run down the list of extreme objects out there.
Colliding white dwarfs, neutron stars and black holes.
Supermassive black holes rotating at close the speed of light gobbling up matter.
Neutron stars crashing through asteroid belts.
Or the evaporation of primordial black holes.
But with some of these possibilities, you would expect to see signals in other wavelengths
like visual, x-rays and gamma rays.
Of course, astronomers have also used the existence of fast radio bursts as proof of
various extreme theories, such as cosmic strings, the collapse of Kerr-Newman black holes, and
even evidence of quantum gravity.
I’ll let you know of any of that pans out.
One of the more extreme ideas is that we could be seeing the blasts of laser transmissions
from alien civilizations, either to communicate, or send their giant starships from star to
star.
Of course, it’s probably not aliens, but it’s fun to imagine it.
CHIME’s discovery of low-frequency radio waves associated with the fast radio bursts
is already helping astronomers filter out some of these ideas.
So here we are, right in the middle of an unfolding mystery.
Unlike dark matter and dark energy, it really looks like this is a mystery that we’re
going to solve sooner than later, thanks to instruments like CHIME which can finally give
astronomers the enormous amount of data they need to work with.
Over time, CHIME will find more of these repeating signals, allowing astronomers places to go
back to again and again to study in detail.
As soon astronomers come up with a more definitive answer, I’ll let you know.
Until then, enjoy watching the mystery unfold.
What do you think?
Let me know your thoughts in the comments.
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