Fast radio bursts – deep space’s newest noisemaker

    The world's largest radio telescope near Arecibo

    The world's largest radio telescope near Arecibo

    Scientists are starting to hear a new kind of message from far across the universe, the question is what (or who) is sending it?

    In 2001, the Parkes Observatory, a massive 210-foot radio telescope in New South Wales, Australia, picked up a strange burst of energy in the sky. Over in just a fraction of a second, it passed into a computer database without raising an eyebrow.

    It wasn’t until 2007 when astronomer Duncan Lorimer, along with a graduate student, were sifting through some old data for a research project, when they noticed the blip.

    “It had very different properties from what we were expecting. It appeared to be much, much further away. So we were completely flabbergasted,” says the West Virginia University professor. “We just didn’t know what to make of it.”

    Neither did the scientific community. The unique signal, called a fast radio burst, was the first of its kind on record. Astronomers informally titled it the ‘Lorimer Burst.’

    “Personally, it is not that important in the grand scheme of things, but it is a nice thing to tell your grandchildren about, I suppose,” he says of the honor.

    Nice, yes, but without a second one on record, there were lots of doubts about what actually caused it. Maybe it was just some radio static, or interference, or a glitch in the software.

    Four years went by–a very nerveracking four years for Lorimer–before anything similar to his burst appeared again in the sky. But then the Parkes telescope grabbed another one, and then recently, and crucially, a different telescope in Puerto Rico spotted a burst, erasing any doubt that these are hiccups in the technology.

    A collection slowly builds

    Despite their massive size, the radio telescopes astronomers like Lorimer rely on for capturing data don’t monitor large sections of the sky. Some describe their relatively narrow beam like having tunnel vision.

    That narrow focus makes it less likely to grab incoming fast radio bursts, which could be arriving from any direction. Today, there’s only ten on record, but scientists think there could be as many as 10,000 of them whizzing toward Earth every day. We just don’t have enough radio telescopes pointed in enough directions to see them all.

    What astronomers do have on record, though, suggests these signals are originating at mind-boggling distances. The clues come from its frequencies.

    “What we can see is that the waves arrive earliest at the telescope at the highest frequencies, and they sort of whistle across our telescope’s range of frequencies,” says Lorimer.

    Lower frequency waves arrive a split-second later, according to Lorimer, because they get slowed down by electrons encountered in space. Higher waves make a cleaner passage.

    By measuring the delay, Lorimer estimates his burst may have traveled one billion light years, opening the door to a wide range of ideas about where they come from.

    Not ruling anything out 

    Professor Lorimer is a big fan of the 1997 Hollywood blockbuster Contact. The movie is based on a book by Carl Sagan and stars Jodie Foster as an astronomer investigating a similar burst of outerspace radio commotion. (Some of the movie was filmed at the Arecibo Observatory in Puerto Rico, where Lorimer worked at the time.)

    Foster’s character determines the source of the waves to be aliens, and eventually takes a trip to meet them.

    “I was trying to hold that one back,” jokes Lorimer, who has heard plenty of comparisons to the film. “Because it is a single pulse, a single event, you could actually imagine an extraterrestrial civilization producing this, either accidentally or on purpose. For instance, during their nuclear wars or something, they could produce an explosion that generates radio emission.”

    Lorimer is a good sport, but he puts the idea of alien nuclear war pretty low on the list of possibilities.

    More likely origins are complex astronomical phenomenons like blitzars, which is a neutron star that, as it collapses into a black hole, sends out a flash of energy.

    Or it could be a flare sent off by the mangled magnetic field of a spinning star called a magnetar.

    “Something more exotic is the evaporation of a black hole, formed in the early universe, due to Hawking radiation,” says Lorimer. “That was very famously proposed by Stephen Hawking about 30 years ago. Again, there would be an associated radio pulse with the final death throes of a black hole. The list goes on.”

    At this point, he says, there are more theories than recorded bursts.

    A useful tool, whatever its origin 

    While astronomers may not yet have a definitive source, they still see huge potential in what they could learn from these signals.

    Keith Bannister is a researcher based in Sydney, Australia, about five hours drive from the Parkes Observatory. (He works for the agency partly responsible for inventing WiFi.)

    Bannister says that the data for each burst doesn’t just provide an indication of how far it traveled, but also the road it took to get here.

    “When we detect one of these bursts, it carries with it a very distinctive signature that we can measure very accurately, and that signature tells you how much gas the burst has gone through,” he says.

    “If we find enough of them, we can essentially weigh how much gas there is in that part of the universe, which is a measurement that hasn’t ever been possible before.”

    With that measurement, scientists could nail down what’s in between galaxies. Or, Duncan Lorimer says, maybe learn more about the magnetic field of the universe. Really big picture stuff.

    “They are not going to solve any of mankind’s problems, right here on earth, you probably already knew that. But for astronomers, they are very interesting…if we can figure out what they are and how far away they are,” says Lorimer.

    Even with more radio telescopes looking for bursts, he says it may take three to five years to answer those questions.

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