One of the biggest mysteries outside the Universe is the nearness to answers. An amazing eight new repeating radio signals known as rapid radio explosions (FRBs) were observed flying from deep space.
At the beginning of 2019, only one of these mysterious signals, FRB 121102, was known to blink repeatedly. In January, scientists reported a second recurring one (FRB 180814).
This new paper – available on the preprint server arXiv, and accepted in The Astrophysical Journal Letters – describes eight new signals repeatedly detected by the Canada Hydrogen Intensity Mapping Experiment (CHIME) radio telescope.
This brings the known number of repeats of FRBs to 1
The rapid burst of radio is certainly worrisome. These are detected as spikes in the radio data, lasting only a few milliseconds. But, at that time, they could emit more energy than 500 million Suns.
Most FRBs are only detected once and are unpredictable, so tracking them back to their source is really tricky (though, as shown earlier this year for the first time, it's not impossible).
That's why repetitions are so important. And the news that they're not as rare as we thought meant that it was possible to track more of their vast resources, and determine what kinds of environments they came from.
We can also begin to find similarities and differences between the repetitions of FRBs.
"There is definitely a difference between sources, with some being more practical than others," physicist Ziggy Pleunis of McGill University told ScienceAlert.
"We already know from FRB 121102 that explosions can be clustered: sometimes the source doesn't explode for hours and hours and then you suddenly get a lot of explosions in a short time. We follow the same item for FRB 180916. J0158 + 65, where we report ten explosions in this paper. "
On the other side of the scale, six of the FRBs have been reported in paper only in one paper, and the longest pause between the signals is over 20 hours. The eighth one (FRB 181119) repeated twice after the initial discovery, pinging a total of three times.
We do not yet know what that means, but it can be argued – as hypothesized in a paper last month by Harvard-Smithsonian astrophysicist Vikram Ravi – that all FRBs are true repeats, but the some are more active than others.
"Some volcanoes are more active than others, and you can imagine a volcano being dormant because it has not exploded in a long time," Pleunis added.
But there are similarities between the FRBs, too. Individual explosions from repeats seem to last a little longer than explosions from one-off FRBs. That is pretty interesting.
There is also a drift frequency. The first two times – the FRB 121102 and FRB 180814 – showed a downward drift in frequency, with each burst successfully descending. Think of a sad trombone sound effect.
At least eight new times, this downward drifting frequency has also been shown. This can be a clue as to what the signals are doing.
"I just think, it's amazing that nature does something like that," Pleunis said. "Also, I think there is some very important information on that structure that we just have to figure out how to encode and it's really fun to try to figure out what that really is."
CHIME was optimized for monitoring a wide-angle sky, across a lower range of frequencies than radio telescopes such as ASKAP or the Parkes Observatory in Australia, which also noted FRB.
To date, the CHIME approach has proven effective in detection. In addition to these repeats, and the repeater announced in January, CHIME saw a number of one-off explosions. It's not optimized for tracking discoveries in a resource, though.
That's where the wider scientific community is. Just recently, another group of researchers, including Ravi, announced that they had made the localization of eight new repeats in known galaxies, based on the direction the signals originated.  We can also tell how far the explosions could have come from based on how the signal was scattered – the higher these steps, the farther the distance.
In fact, this is where it gets interesting, as one of the signals, The FRB 180916, has the lowest dispersion ever seen, suggesting it may be close.
"Even with the largest telescope, if it's near you, you always get a better view than if it were farther away," astronomer Keith Ang Bannister from the Australian national science agency CSIRO , who was not involved in the research, told ScienceAlert.
"So it's not particularly low proportions that are so exciting, because there's a good chance it will be close. It means it's easier to see, once we really know where it is in the sky."  The polarization of the signals (how the signal is bent) is informative. If the signal is indeed bending, it means that it originates in an intense magnetic environment, as can be found around a black hole or neutron star. This is the same signal from FRB 121102.
But the team was able to measure the polarization of one of the new signals, FRB 180916, and it was really low. We are told that not all repeated FRBs come from extreme environments.
We do not yet know what this means. We do not know that there are many different types of objects or events that produce these signals. We do not know if they are all repeated, or why they are repeating. But these results bring us amazingly close to finally having some answers.
"I think (and I hope!) The paper will prompt other astronomers to point their telescopes to these newly discovered sources," Pleunis said.
"Then, there is a lot of information here for model proponents to help them figure out what makes repeated FRBs.
" Also, in my opinion, our findings can influence in the strategy of finding other teams to try to discover repeated FRBs. "
The research was accepted into The Astrophysical Journal and available in arXiv.