Cosmic heartbeat offers clues to expansion of universe
By Heather Allen
Life on Earth is beginning to look like the opening pages of a science fiction novel, and a dystopian one at that. We’ve had an unprecedented heatwave in the UK, with parliament fiddling while London burns. The ice caps are melting as the poles heat up, we’ve had a devastating pandemic with rumblings of more to come, plus a smorgasbord of anomalous floods, earthquakes, wars, political unrest and other unsettling shenanigans across the globe. Business as usual in the 21st Century.
Meanwhile, in chapter two of 2022: The Novel, a whole host of fascinating and occasionally alarming scientific discoveries and innovations are emerging. Google’s AI chatbot has been accused of gaining sentience, quantum computers are in production (although as yet prohibitively expensive for the likes of us), and nanobots are being developed which are capable of crawling around inside the cells of your body. Asimov would be rubbing his hands together with glee (while no doubt nervously reminding us about his Three Laws of Robotics).
On the astronomical level, it seems only a matter of time before life is discovered on other planets – or it discovers us. We all gasp at the shiny images from the James Webb Space Telescope, obviously superior to the Hubble, in a world where anyone who lives in a city can barely see any stars in the night sky. It seems pure arrogance to assume that there’s no other sentient life out there.
Into this landscape comes the latest discovery by astronomers at the Massachusetts Institute of Technology (MIT), the same educational institution which in 1972 predicted that society would collapse in the mid 21st century (we’re ahead of schedule on that, but that’s another story). Astronomers at MIT, along with colleagues in Canada and across the USA, have detected a fast radio burst (FSB) coming from a distant galaxy which appears to be flashing with surprising regularity. The signal persists for up to three seconds, which is around 1,000 times longer than the average FRB. Within this three-second window, MIT astronomers have detected bursts of radio waves that repeat every 0.2 seconds in a clear periodic pattern, like a cosmic heartbeat. Researchers have given the signal the snappy label FRB 20191221A, and it is the longest-lasting FRB, with the clearest periodic pattern, detected to date.
This unusual, persistent radio signal originates from a distant galaxy several billion light years from Earth. What that source might be is uncertain, but astronomers believe that the signal emanates from either a radio pulsar or a magnetar, both types of neutron stars – extremely dense, rapidly spinning collapsed cores of giant stars. Whatever it is, it’s certainly got the attention of Earthlings.
“There are not many things in the universe that emit strictly periodic signals,” Dr Daniele Michilli, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research, said. “Examples that we know of in our own galaxy are radio pulsars and magnetars, which rotate and produce a beamed emission similar to a lighthouse. And we think this new signal could be a magnetar or pulsar on steroids.”
The team hopes to detect more periodic signals from this source, which they say could be used in future as an astrophysical clock. The frequency of the bursts, and how they change as the source moves away from Earth, could be used to measure the rate at which the universe is expanding.
Since the first FRB was discovered in 2007, hundreds of similar radio flashes have been detected across the universe, most recently by the Canadian Hydrogen Intensity Mapping Experiment, (CHIME), an interferometric radio telescope consisting of four large parabolic reflectors.
CHIME is designed to pick up radio waves emitted by hydrogen in the very earliest stages of the universe. The telescope is sensitive to fast radio bursts and has identified hundreds of new FRBs. The vast majority of these FRBs are one-offs. However, FRB 20191221A, first picked up on December 21 2019, was not. This signal consisted of a four-day window of random bursts that were then repeated every 16 days.
After analysing FRB 20191221A’s radio bursts, Dr Michilli and his colleagues found similarities with emissions from radio pulsars and magnetars in our own galaxy – except that FRB 20191221A was more than a million times brighter.
“It was unusual,” Dr Michilli said in a classic astrophysicist understatement. “Not only was it very long, lasting about three seconds, but there were periodic peaks that were remarkably precise, emitting every fraction of a second – boom, boom, boom – like a heartbeat. This is the first time the signal itself is periodic.
“CHIME has now detected many FRBs with different properties. We’ve seen some that live inside clouds that are very turbulent, while others look like they’re in clean environments. From the properties of this new signal, we can say that around this source, there’s a cloud of plasma that must be extremely turbulent.”
The astronomers hope to catch additional bursts from the periodic FRB 20191221A, which they say will help to refine their understanding of its source and of neutron stars in general. The James Webb Space Telescope will be a big help in this enterprise, just as the Hubble space telescope has been in the past, and reveal new clues about the origins of the universe.
It’s only a matter of time before we discover that something in the universe is looking right back at us. Hopefully they will send a message if they’re popping over for a visit, and a fast radio burst seems the ideal way for a space consciousness to get in touch. True, FRB 20191221A is unlikely to be an alien ‘Hello’, but it’s proof enough that the technology exists to pick up communications from deep space. Let’s just hope that, when it happens, we recognise it for what it is and are able to act appropriately.