Astronomers detect radio burst from 8 billion years ago
Astronomers have picked up a radio signal from eight billion years ago, meaning it’s traveled more than half the age – and width – of the observable universe to get here. Thanks to its extensive experience in the cosmos, the signal can actually help us track down “missing” matter.
Designated FRB 20220610A, this signal belongs to a class known as fast radio bursts (FRBs). As the name suggests, these are sharp bursts of radio waves that last mere milliseconds, and seem to pour in from all corners of the sky. Their exact origin remains unknown, but the prime suspect is a highly magnetized form of neutron stars called a magnetars, which have been caught firing off suspiciously FRB-like signals.
Most FRBs detected so far have come from hundreds of million light-years away, or out to a few billion. The closest was just a few tens of thousands of light-years – within our own Milky Way. But the new detection, made on June 10, 2022, is now the most distant FRB ever spotted. At a distance of eight billion light-years, the team says it’s likely close to the limit that modern technology can pinpoint them.
“Using ASKAP’s array of dishes, we were able to determine precisely where the burst came from,” said Dr. Stuart Ryder, first author of the study. “Then we used the European Southern Observatory (ESO) Very Large Telescope (VLT) in Chile to search for the source galaxy, finding it to be older and further away than any other FRB source found to date, and likely within a small group of merging galaxies.”
The team says that the study also shows that FRBs can be put to work helping astronomers solve another cosmic mystery: that of the missing matter. Our best models of the universe indicate it should contain a certain amount of matter, but when scientists tally up all the galaxies, stars, planets, black holes, and everything else, there seems to be a huge shortfall – we’re missing about 40% of the budget of normal matter (as opposed to dark matter, which is a completely different thing).
The leading hypothesis is that all this matter takes the form of extremely diffuse gas floating around in intergalactic space. It’s so thin that it’s almost impossible to detect, but that’s where FRBs come in. Astronomers can study the arrival times of different wavelengths of light in those radio signals, and from that it’s possible to infer the density of matter they’ve passed through. The longer the journey, the more data it contains, which makes this new one such a treasure trove. And sure enough, the new observations seem to be in keeping with the diffuse intergalactic gas hypothesis, providing some of the strongest evidence to date.
“While we still don’t know what causes these massive bursts of energy, the paper confirms that fast radio bursts are common events in the cosmos and that we will be able to use them to detect matter between galaxies, and better understand the structure of the Universe,” said Associate Professor Ryan Shannon, co-lead author of the study.
The research was published in the journal Science.