Three and a half billion years ago, a mysterious object on the edge of a distant galaxy spewed forth an intensely bright, vanishingly brief burst of radio energy that shot across the universe.
That pulse of energy — known to its fans in the astronomy community as a fast radio burst (FRB) — passed through a wilderness of gas, dust and empty space on its multi-billion-year journey, slowly stretching and changing color as it moved. Then, for less than a millisecond in 2018, that burst zapped past a special telescope in Earth's Australian outback, giving scientists a rare opportunity to shake hands with one of the most mysterious forms of energy in the universe.
It's the first time that astronomers have successfully tracked a one-off FRB back to its origins across space and time, according to the authors of a study published today (June 27) in the journal Science. Understanding where FRBs come from allows scientists to probe the vast tracts of matter between their host galaxies and Earth, and maybe even locate undiscovered pockets of protons and neutrons thought to be lurking between galaxies.[The 12 Strangest Objects in the Universe]
"These bursts are altered by the matter they encounter in space," study co-author Jean-Pierre Macquart, a researcher at the International Centre for Radio Astronomy Research (ICRAR) said in a statement. "Now we can pinpoint where they come from, we can use them to measure the amount of matter in intergalactic space."
Bursting onto the scene
Since the phenomenon was discovered in 2007, astronomers have observed about 85 FRBs and pinpointed the origins of only one other — a repeating flash that pulsed 9 times from a tiny, star-forming galaxy over about six months in 2016. Pinpointing the source of a one-off FRB, which can last for a fraction of a millisecond, has proved exceedingly difficult, until now.
In their new study, the researchers detected the lone FRB using an array of 36 satellites called the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. When an FRB passes the array, each satellite picks up the burst's signal a fraction of a millisecond apart. Using these subtle time differences, the researchers were able to figure out which direction the burst came from, and approximately how far it traveled.
The ASKAP observations pointed to a Milky-Way-size galaxy about 3.6 billion light-years away from Earth. With some help from several other large telescopes around the world, the researchers zoomed in on this galaxy to learn that it was relatively old and not forming many new stars.
According Adam Deller, an astrophysicist at Swinburne University of Technology in Australia and co-author of the new study, the properties of this distant galaxy sit in stark contrast to the galaxy that created a repeating fast-radio burst that was detected in 2016.
"The burst we localized and its host galaxy look nothing like the 'repeater' and its host," Deller said in the statement. "It comes from a massive galaxy that is forming relatively few stars. This suggests that fast radio bursts can be produced in a variety of environments."
While the repeating FRB detected a few years ago was likely created by a neutron star or supernova explosion (common engines of star formation in active galaxies), this individual burst could have been caused by something else entirely, the researchers wrote.
What else, exactly? Nobody knows yet — but radioactive belches from supermassive black holes or the engines of alien spacecraft have not been ruled out. Only by pinpointing more FRBs will researchers be able to unravel this cosmic mystery. Fortunately, the authors of the new study wrote, now that they've got one under their belt, finding the next one should be a little easier.
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Originally published on Live Science.