While the first photographs from the James Webb Space Telescope are getting all of the love and media attention – and rightly so – the real work in the search for extraterrestrial intelligence is still being done by radio telescopes and the scientists who search for unusual radio signals and their sources. Those who follow the news of these signals know that one is good, two is better because it means it’s a repeater, and three is excellent because it tells if the repeating signal is regular or irregular – with regular being a sign it could be being sent by an intelligent civilization with the technology to generate massive blasts on schedule. Astronomers at MIT just upped the signal search a notch with the announcement this week that they have detected a clear and periodic pattern of fast radio bursts from a distant location. Just to make sure the mainstream media was paying attention, they compared its periodicity to a “heartbeat.” Did that get YOUR attention?
“The source of the signal lies in a distant galaxy, several billion light-years from Earth. Exactly what that source might be remains a mystery, though astronomers suspect the signal could emanate from either a radio pulsar or a magnetar, both of which are types of neutron stars — extremely dense, rapidly spinning collapsed cores of giant stars.”
A mysterious heartbeat from deep space. MIT scientists aren’t known for waxing poetic but this could be the perfect subject for a quatrain or two. The signal has been stuck with the non-poetic name FRB 20191221A. Discoverer Daniele Michilli, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research, announced it in the journal Nature and in an MIT press release. With co-authors co-authors Calvin Leung, Juan Mena-Parra, Kaitlyn Shin, and Kiyoshi Masui, Michilli detected the mysterious signal using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) an interferometric radio telescope located at the Dominion Radio Astrophysical Observatory in British Columbia. CHIME is the equivalent of the James Webb telescope in the field of fast radio bursts, having discovered hundreds in just three years. FRB 20191221A is the longest-lasting FRB and has the clearest periodic pattern ever found.
“It was unusual. 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.”
Michilli should have put more emphasis on the ‘very’ in “very long” – virtually all other fast radio bursts are milliseconds in length, making this one unusual in more ways than one. First detected on December 21, 2019, it was still early in the discovery phase of FRBs so Michilli and his team initially could only guess at what might be emanating this massive radio heartbeat from such a long way from the Milky Way – an estimated several billion light-years away. Initially, it was thought that the powerful signals were coming from black holes or neutron stars – the end results of explosive supernovas. However, in 2020, astronomers were surprised when SGR 1935+2154, a magnetar discovered in the constellation of Vulpecula in the Milky Way galaxy, radiated a fast radio burst – the first time a magnetar was known to create them. Magnetars are highly magnetized, ultradense neutron stars, and Michilli noted that FRB 20191221A was acting like one … kind of.
“There are not many things in the universe that emit strictly periodic signals. 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.”
“A pulsar on steroids” isn’t exactly poetic, but it aptly describes FRB 20191221A. The ‘heartbeat’ appears to be a million times brighter than the pulsars and magnetars in the Milky Way. Michilli suspects the source of FRB 20191221A is either a pulsar or a magnetar that rotates like a lighthouse does – emitting bright flashes between dark periods. However, he thinks something happened just as CHIME was pointed at it -- FRB 20191221A ejected an extremely brilliant burst with regular beats in that long three-second interval before going out again. Those three seconds seem brief to us, but they were long enough for Michilli to make another determination about FRB 20191221A.
“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.”
Turbulent Cloud of Plasma sounds like a band name more than a line of poetry, but it makes this an even bigger discovery than first thought. The good news is, the astronomers now know where to look for the next fast radio burst from FRB 20191221A. the better news is that now astronomers have a different set of characteristics to search for when scanning the galaxies for fast radio bursts using CHIME or FAST – China’s Five-hundred-meter Aperture Spherical Telescope, which is already picking up pulsars. The behavior of FRB 20191221A will also help in the design and use of future radio telescopes.
“Such short periodicity provides strong evidence for a neutron-star origin of the event. Moreover, our detection favours emission arising from the neutron-star magnetosphere, as opposed to emission regions located further away from the star, as predicted by some models.”
While Michilli and his team can’t tell us exactly what sent the heartbeat known as FRB 20191221A, it can tell us it is probably an extremely powerful magnetar that is an outlier in the world of fast radio bursts because of its duration and pulse profile. It is also a regular periodic repeater, the first of its kind ever discovered. If that doesn’t qualify FRB 20191221A for a poem, can it at least get a better name … maybe a musical one? Hungry Heart? Heart of Gold? If Bruce Springsteen or Neil Young gets to name this unique signal, would that make one them the Owner of a Lonely Heart?