The New CHIME Telescope Detected 500 Mysterious Radio Bursts in One Year
The best things in life are fleeting, and in radio astronomy, they are also among the brightest ever seen.
A telescope in British Columbia detected more than 500 new fast radio bursts in its first year of operation, between 2018 and 2019, according to a briefing streamed live via YouTube of an American Astronomical Society Meeting on Wednesday.
No one is sure what creates the fast radio bursts (FRBs), but this represents a significant step in continuing to map the universe.
The growing catalog of ultra-high-energy fast radio bursts
Like seeing a shooting star with the naked eye, catching a fast radio burst with an advanced telescope involves a great deal of luck in when and where you point a radio dish. FRBs are mysteriously bright flashes of light that register in the radio band of the electromagnetic spectrum, and burn bright for mere milliseconds before vanishing as quickly as they appeared.
While brief, these intense cosmic beacons have been seen in various distant sectors of the universe, including in our Milky Way. We don't know where they come from, and their presence is fundamentally unpredictable. The first ones were spotted in 2007, and since then radio astronomers had only witnessed roughly 140 bursts within their scopes. But a large stationary radio telescope in British Columbia nearly quadrupled the number of recorded FRBs. Called the Canadian Hydrogen Intensity Mapping Experiment (CHIME), the telescope has identified 535 new FRBs in its first year of operation, in an unprecedented contribution to radio astronomy.
Scientists participating in the CHIME Collaboration included some from MIT, and together they have gathered the newest signals in the FRB catalog of the telescope, presenting their findings in this week's American Astronomical Society Meeting. This expanded catalog of FRBs might offer clues about the properties of the phenomenon. For example, the new batch of mega-bursts seems to come in two types: repeating and non-repeating. Eighteen FRB sources saw repeated bursts, but the rest came and went, never to appear again. But the repeating bursts also appeared different, with each one lasting mildly longer and achieving more focused radio frequencies, compared to the single, one-off FRBs.
This suggests repeaters and singular FRBs come from different cosmic mechanisms or astrophysical sources. If astronomers are given more time to study them, we might soon learn the source of these monstrous signals. "Before CHIME, there were less than 100 total discovered FRBs; now after one year of observation, we've discovered hundreds more," said Kaitlyn Shin, a CHIME member and graduate student in MIT's Department of Physics, in an embargoed press release shared with IE. "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."
Most of the new FRBs come from very distant, very old galaxies
The CHIME telescope is comprised of four colossal parabolic radio antennas, each the size and shape of a snowboarding half-pipe. The array is located in the Dominion Radio Astrophysical Observatory in British Columbia, Canada. Every day, the telescope picks up radio signals from half the sky as the planet rotates beneath it. But it has a unique advantage: instead of swiveling a big dish at the sky like in the sci-fi classic film "Contact", CHIME simply stares, seemingly dead-eyed and motionless at the sky, honing in on incoming signals via a correlator, which is a potent digital signaling processor capable of processing vast quantities of data, at an impressive rate of 7 terabits per second.
In case you missed it, this is roughly the same as a few percentages of the entire world's internet traffic. "Digital signal processing is what makes CHIME able to reconstruct and 'look' in thousands of directions simultaneously," said Kiyoshi Masui, an assistant professor of physics at MIT who led the group presentation at the Wednesday conference. "That's what helps us detect FRBs a thousand times more often than a traditional telescope."
This is a major accomplishment not only for such a young telescope, but for radio astronomy itself. When radio waves burn through the universe, interstellar gas or plasma in its path can distort or disperse the properties of the radio wave, in addition to its trajectory. The more dispersed it is, the more astrophysicists and radio astronomers can surmise about the "life" of the FRB, in addition to how far its come. This was done for every one of the 535 FRBs, and most of them likely came from galaxies unconscionably far away, which also means a long, long time ago. Learning what in the scientific universe could be energetic enough to emit FRBs could even transform our grasp of the early universe.
The team had to work out how to enhance both HTC and CHF by adding a series of microscale cavities (dents) to a surface.