Researchers have detected a strange repeating rhythm of Fast Radio Bursts (FRBs) emanating from an unknown source outside our galaxy, 500 million light-years away.
Fast radio bursts, or FRBs, are short, intense flashes of radio waves that are thought to be the product of small, distant, extremely dense objects, though exactly what those objects might be is a longstanding mystery in astrophysics.
FRBs typically last a few milliseconds, during which time they can outshine entire galaxies. Since the first FRB was observed in 2007, astronomers have catalogued over 100 fast radio bursts from distant sources scattered across the universe, outside our own galaxy.
Now astronomers have started to find bursts repeating in a pattern, where they seem to switch off and on in a predictable pattern. The latest discovery, published in the journal Nature, sends out random bursts of radio waves over a four-day window, and then goes quiet for 12 days, before beginning again.
Researchers watched the bursts for more than 500 days, noting that the 16-day pattern occurred consistently over that time, making it the most definitive pattern yet seen.
"This FRB we're reporting now is like clockwork," said study researcher Kiyoshi Masui from Massachusetts Institute of Technology (MIT) in the US.
"It's the most definitive pattern we've seen from one of these sources. And it's a big clue that we can use to start hunting down the physics of what's causing these bright flashes, which nobody really understands," Masui added.
The latest FRBs were picked up by CHIME, that was the first to pick up signals of the new periodic FRB source.In 2017, CHIME was erected at the Dominion Radio Astrophysical Observatory in British Columbia, where it quickly began detecting fast radio bursts from galaxies across the universe, billions of light-years from Earth.
CHIME consists of four large antennas, each about the size and shape of a snowboarding half-pipe, and is designed with no moving parts. Rather than swivelling to focus on different parts of the sky, CHIME stares fixedly at the entire sky, using digital signal processing to pinpoint the region of space where incoming radio waves are originating.
From September 2018 to February 2020, CHIME picked out 38 fast radio bursts from a single source, FRB 180916. J0158+65, which the astronomers traced to a star-churning region on the outskirts of a massive spiral galaxy, 500 million light-years from Earth.
The source is the most active FRB source that CHIME has yet detected, and until recently it was the closest FRB source to Earth.As the researchers plotted each of the 38 bursts over time, a pattern began to emerge: One or two bursts would occur over four days, followed by a 12-day period without any bursts, after which the pattern would repeat.
This 16-day cycle occurred again and again over the 500 days that they observed the source.
"These periodic bursts are something that we've never seen before, and it's a new phenomenon in astrophysics," Masui said.
The researchers noted that the blasts could also be the result of a binary system such as a neutron star orbiting around another neutron star or black hole. The pattern could be the result of the orbit between, and the interaction between the two objects, which would explain their regular pattern, they concluded.