Astronomers have detected 13 bursts of high-speed radio waves coming from deep space – including one that repeats regularly. While the exact sources remain unknown, the new band of mysterious explosions offers new clues as to where and why such flashes appear throughout the cosmos.
Rapid radio explosions, as they are known by scientists, are among the most bizarre phenomena in the universe. Each explosion lasts only milliseconds, and they all seem to be coming from far away from our galaxy, the Milky Way.
Since those explosions were discovered in 2007, their cause remained a puzzle. Based on estimates of the known range of their frequencies and an understanding of the activity in the universe, scientists expect almost a thousand of them to happen every day. But to this day, only a handful has been found.
Now a team using the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, has announced the 13 new additional detections, including a particularly rare repeated explosion. So far, just another fast radio blast was known.
"The repeater," as it is being called, and its 12 counterparts came from a region of space about 1.5 billion light-years away, the team said in the magazine today. Nature. All 13 new bursts have the lowest radio frequency ever detected, but they have also been brighter than the fastest radio bursts, prompting the team to think that low frequency has something to do with the source environment.
"That does not mean they're traveling from a distance," says study author Shriharsh Tendulkar, a postdoctoral fellow in the physics department at McGill University. "As light propagates through the hot gas and plasma in the intergalactic medium and in the interstellar medium, it has a lot of different effects on the signal."
For example, radio waves are distorted as they travel through space and can disperse or be absorbed by gas and plasma. The team therefore believes that all 13 explosions probably originated from dense and turbulent regions within their host galaxies, particularly areas with a lot of violent activity, such as dense remnants of supernovae or near black holes.
Deepening the mystery
Tendulkar and the team also noted that the structure of the new repeat burst is remarkably similar to the only other repeater ever found.
"The fact that we saw these multiple structures in the burst was very similar to the first repetitive fast radio burst. This is very unusual, "he says. "There is now such tempting evidence that the structures of these explosions are seen only in repeaters." This suggests that if faster radio bursts are found with this structure, they may be the prime candidates for repeaters.
The repeated new explosion is brighter than the previous detection, which may be due to the fact that it is 1.5 billion light years closer, but the team can not be sure of that. To make further comparisons, they will have to search the heavens for the host galaxy of the new explosion, which is not a guaranteed finding. Meanwhile, the team continues to use CHIME to observe the sky region from which these explosions came, as well as using other radio telescopes to track the findings.
"We are trying to build clues and trying to understand whether the rapid and repeated radio blasts and the rapid radio bursts are different populations," says Tendulkar. "Do they come from different objects? Or are they related in some way to the other? We're trying to figure out these things, so that's really exciting. "
Also, when CHIME detected these new blasts, it was only working at a fraction of its capacity, and the team is excited to see how many more will appear in their data now that the instrument is fully operational.
"The discovery of CHIME points to enormous potential," says Shami Chatterjee, senior researcher at the Center for Astrophysics and Planetary Science at Cornell, who was not involved in the latest discoveries. "I am intensely curious to know how many [fast radio bursts] they are sitting now. They must have tens or hundreds.
Finding even more explosions means that strange occurrences can be effective tools for understanding the traces of gas, dust, and plasma that exist in the seemingly empty space between galaxies called the intergalactic medium, Chatterjee adds.
"Everyone agrees that in the intergalactic environment, it is very difficult to have a probe that can tell you about your make-up," says Chatterjee. "It is an order of magnitude more empty than our interstellar medium, but because of the [fast radio bursts] what we are discovering now will be one of the few ways we can investigate this medium and understand these environments. "
And for now, Tendulkar notes that the mystery surrounding rapid radio bursts remains part of his appeal.
"There's a lot of fun not knowing," he says. "You keep adding more information, but like in every science, whenever you solve a mystery, it always opens three more."