Even though the sky looks about the same every night to those of us here on Earth, cataclysmic things happen in outer space constantly. Like right now and now and also now. And for the first time in history, astronomers like Simon Johnston and Emily Petroff are able to watch the split-second action as it goes down.
On May 14, 2014, Johnston sat at home in Australia, operating the Parkes Radio Telescope from his personal computer. The observations went along sleepily, as he watched waves of static on the computer screen. And then it appeared: a flash of radio waves that lasted just 2.8 milliseconds but unleashed more energy than the sun does in a whole day.
A signal of this sort—called a "fast radio burst"—is the elusive white stag of astronomy. Until earlier that year, their very existence had remained a question mark. No one had seen one happen. Until Johnston did. Right away, he told 12 telescopes spread across the world—sensitive to optical, infrared, gamma-ray, X-ray, and radio radiation—to swivel to the same spot in the sky. But the stag was gone, having left no hoof-prints.
But seeing it in the wild at all was a big deal, and something we’ve only had the tools to do for a few years. Scientists still don't know why fast radio bursts happen—only that they represent a faster explosion of energy than humans have ever previously recorded in space.
“We’ve had a huge leap in technological capability,” says Emily Petroff, the lead author on the burst’s discovery paper. “We have a great rack of computers that does almost instantaneous processing of a huge amount of data.” That great rack chops the 1,024 different radio frequency channels into 32-microsecond chunks. For the record, that’s 31,250 chunks per second, more than 500 times faster than an HD video’s frame-rate, producing 48 Megabytes of data every second. Today’s observatories often have their own supercomputers, which funnel, sort, strip, and calibrate to produce the cosmic movie as it plays out. This hardware dishes up the results in a way that a human astronomer—whose brain can’t parallel-process quite as efficiently as the Graphical Processing Units (GPUs) that make this all possible—can digest.
In other words, astronomy doesn’t just make glamour shots anymore: It makes biopics, giving a more realistic depiction of what the cosmos are really like. For millennia, astronomy has mostly felt like the study of static objects, because we live for 85 years and stars sometimes live for 8.5 billion. But today’s telescopes and their companion computers (which astronomers call “backends”) show us a universe that also changes in hours, days, and milliseconds.
Astronomers call this field of study “time domain astronomy.” “It’s opening up a brand-new way of looking at things,” says Petroff. “We’re so used to thinking of things that happen on billion-year timescales—the evolution of the universe in the big picture—but these bursts allow us to look at the universe on a small scale.”
The first bursts ever discovered, however, didn’t receive as warm a welcome as Petroff’s real-time discovery did. Astronomers (and husband-wife duo) Duncan Lorimer and Maura McLaughlin found the first one by accident in 2007. They were combing through 30-year-old data from the Parkes Telescope, just looking for new pulsars. Pulsars are the superdense cores left after supernova explosions. Each time they spin around, a beam of radio waves shines in Earth’s direction, just like the passing beam of a lighthouse. Lorimer sometimes demonstrates this to students by turning in circles while holding a meter-stick, his faded T-shirts (often screenprinted with black-hole jokes) flapping around him. (I know this from my time working in the National Radio Astronomy Observatory's education department, where I helped run a program that let students find pulsars in Green Bank Telescope data. That's where I first met Lorimer and McLaughlin.)
Pulsars show up in plots like the regular blip blip blip of your heartbeat on a monitor. But while looking for those cosmic heartbeats, Lorimer noticed something strange: a single, non-repeating blip. Or, actually, a BLIP!!!!!. It released as much radiation in 5 milliseconds as the sun does in a month. And it seemed to be coming from 3 billion light-years away—that is: way, way outside our galaxy.
And just like that it was never seen again. People started calling it the “Lorimer burst.” Other astronomers began publishing papers about what it could be: a primordial black hole? The cusp of a cosmic string? An unknown reaction from a supernova explosion? Two neutron stars crashing into each other? These are the X-Games of astronomy.
But time continued passing, as it is wont to do. And scientists started to doubt, as they are wont to do, when no one but Lorimer could find a Lorimer burst. “All we had were a few milliseconds data from the late 1990s,” McLaughlin previously told me.
Then, in 2011, a group led by Sarah Burke-Spolaor, then a postdoctoral researcher at the Commonwealth Scientific and Industrial Research Organisation in Australia, offered a stunning alternative theory: The exotic flashes might come from right here on Earth. The team had found 16 Lorimer-like pulses, but showed they were just blasts from Earth’s atmosphere—merely mimicking faraway signals. Perytons, Burke-Spolaor called them. (The name comes from a Jorge Louis Borges story, referring to a (fictional) stag-bird hybrid—half Earth-bound, half not.) After that, many people “stopped wondering about” the Lorimer burst. At one conference talk, a heckling audience member even asked attendees to please raise their hands if they “believed the Lorimer burst.”
But three years later, in 2014, the same scientist who’d derided the burst as a peryton declared that now she, too, had seen a milliseconds-long BLIP!!!. And it wasn’t a stag-bird.
That summer, another team found four more. “They had found one at a time for a long time,” says Petroff. But when they found four in the same set of data (and one from a telescope other than Parkes), naysayers couldn’t hand-wave them away. Now, everybody believed Duncan’s bursts, which they had renamed the more professional “fast radio bursts,” or FRBs for short.
Around the same time that her colleagues began drafting the four-burst paper, Petroff began graduate school at Swinburne University. “It became my job to look for more of these FRBs,” she says.
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We still don’t know what in space acts that fast—partly because we only recently have the ability to see the sky change that fast. No one knew the Moon had craters until Galileo pointed his fancy new telescope—with high spatial resolution—at it. No one knew FRBs slashed through space until we pointed our even newer, fancier telescopes at them. Just as Galileo couldn’t guess why the moon has craters until he knew the craters existed, modern scientists couldn’t figure out why FRBs happen until they knew FRBs happened. “Any time you open up new parameter space, you find something unexpected,” says Petroff. “I’m willing to believe FRBs come from something we haven’t thought of before.”
Historically, we’ve made important discoveries in the slower-style “time domain.” In the beginning, people who sat around obsessively watching the sky noticed that a few bright dots moved across the sky faster than other bright dots. Planets! Sometimes, fuzzy streaks appeared and then disappeared. Comets!
Using a device that blinked between telescope images of the same spot, like a (boring) celestial Viewmaster, Henrietta Leavitt discovered in 1912 a type of star whose varying brightness gives away cosmic distances. Later, these stars allowed Edwin Hubble to discover what a galaxy is, and that we live in one. Exploding supernovae led to the discovery of dark energy. Intelligence analysts found gamma-ray bursts while spying on Russian nuclear tests. The list goes on, but I will stop.
As technology has gotten better, the timespans we can discern have gotten shorter. Where we once tracked planets’ movements by hand to discover they were planets, we now measure second-to-second how the wind blows on Mars. Where we once would not have been able to see a 3-millisecond burst because we only took data in 30-second increments, we now see it when it occurs and command telescopes around the world to point to the same spot.
Today’s technology is not just letting us see the universe—it is letting us watch the universe happen. And it’s awe-inspiring.
We can see planets pass in front of stars. We can scrutinize the Sun’s magnetic loops as they tangle themselves up. We can shoot a radar at asteroids as they slide between us and the Moon. We can even watch asteroids crash into each other in other solar systems. A gas cloud’s close encounter with the black hole at the center of our galaxy? Astronomers tuned in to that daily like a sitcom.
But even the best astronomer doesn’t really understand what a billion years is. How could any of us? “An abstract, intellectual understanding of deep time comes easily enough—I know how many zeroes to place after the 10 when I mean billions,” said author Stephen J. Gould. “Getting it into the gut is quite another matter. Deep time is so alien that we can really only comprehend it as metaphor.”
Metaphors like the Cosmic Calendar of Cosmos fame, for instance. If you compress the history of the universe into a year, the Big Bang would have happened when the ball dropped on January 1, and the last Neanderthal would have died at 11:59 p.m. on December 31. It helps us see how long time in general is, and how short our time is.
But it’s also important to remember that with every tick of that metaphorical (and the literal) second-hand, the universe becomes a different place. And now with high-performance backends, we can actually find out what its growth and change look like. We can see how microseconds add up to seconds, seconds to minutes, minutes to hours. And maybe someday we will comprehend how hours become billions and billions of years.
Maybe to understand “deep time,” we first have to understand shallow time. After all, it’s the way we experience our own existence. As Annie Dillard said, “How we spend our days is, of course, how we spend our lives.” The same is true of the universe and its milliseconds.
This article was originally published at http://www.theatlantic.com/technology/archive/2015/02/what-its-like-to-watch-the-faraway-universe-in-real-time/385356/
