A radio signal sent from deep space eight billion years ago is the oldest and most distant ever detected – but astronomers are not sure what caused it.
Known as a ‘fast radio burst’ (FRB), the remote blast of cosmic radio waves lasted less than a millisecond, but is so powerful that it released the same emissions as our Sun over 30 years.
FRBs can be so bright that they outshine the galaxy they came from.
First discovered in 2007, around 1,000 FRBs have so far been detected – but their origins remain a mystery.
Some believe they could be alien signals, sent in an attempt to make contact with Earth. Others argue they may be caused by magnetars, super-dense dead stars with incredibly strong magnetic fields that blast out pulses of radio waves as they spin at lightning speeds.
The latest addition has been snappily named FRB 20220610A, and was detected by astronomers in June last year using the ASKAP radio telescope on Wajarri Yamaji Country in Western Australia.
While the team does not know exactly what caused it, they have pinpointed its source, a group of two or three galaxies that are merging, supporting another theory on the cause of fast radio bursts.
‘Using ASKAP’s array of dishes, we were able to determine precisely where the burst came from,’ said co-lead author Stuart Ryder, an astronomer from Macquarie University in Australia.
‘Then we used [European Southern Observatory’s Very Large Telescope] 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 study, published in the journal Science, also confirms that FRBs can offer a new way to ‘weigh’ the universe, by measuring the missing matter between galaxies.
‘If we count up the amount of normal matter in the universe – the atoms that we are all made of – we find that more than half of what should be there today is missing,’ said co-lead author Ryan Shannon, a professor at the Swinburne University of Technology in Australia.
‘We think that the missing matter is hiding in the space between galaxies, but it may just be so hot and [spread out] that it’s impossible to see using normal techniques.
‘Fast radio bursts sense this ionised material. Even in space that is nearly perfectly empty they can “see” all the electrons, and that allows us to measure how much stuff is between the galaxies.’
The research also showed that eight billion years is about as far back as astronomers can expect to see and pinpoint FRBs with current telescopes.
However, new telescopes are in the works to help detect even older and more distant bursts – and detect where they came from.
The international Square Kilometre Array Observatory is currently building two radio telescopes, one in South Africa and one in Australia, that will be capable of finding thousands of FRBs, including very distant ones that cannot be detected with current facilities.
The ESO’s Extremely Large Telescope, a 39-metre telescope under construction in the Chilean Atacama Desert, will be one of the few telescopes able to study the source galaxies of bursts even further away than FRB 20220610A.
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