Transients are usually connected with some of the most energetic and violent events in the Universe, such as the death of massive stars. That’s why objects that do change (known as variables) or appear and disappear (known as transients) are so interesting. Most things astronomers see in outer space are fairly stable and don’t change much on human time scales. We have been surveying the sky with ASKAP throughout 20 in search of unusual new objects, in a project called the Variables and Slow Transients (VAST) survey. ![]() ![]() A strange signal from the heart of the Milky Way Despite our best efforts, we are still unable to work out exactly what produced these mysterious radio waves. We first spotted the signal using the Australian Square Kilometre Array Pathfinder Telescope (ASKAP), then followed up with other telescopes around the world and in space. What’s more, the radio waves in the signal had an uncommon “circular polarisation”, which means the electric field in the radio waves spirals around as the waves travel through space. The signal blinked on and off, growing 100 times brighter and dimmer over time. "For instance, 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," the press release reads.In early 2020, we detected an unusual radio signal coming from somewhere near the centre of our galaxy. ![]() More periodic signals from this source could be used as an astrophysical clock. "Future telescopes promise to discover thousands of FRBs a month, and at that point we may find many more of these periodic signals." "This detection raises the question of what could cause this extreme signal that we've never seen before, and how can we use this signal to study the universe," said Michilli. The detection could help them as they study the universe and neutron stars. They hope to catch more bursts from FRB 20191221A. 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." "We've seen some that live inside clouds that are very turbulent, while others look like they're in clean environments. "CHIME has now detected many FRBs with different properties," said Michilli. These are dense, rapidly spinning collapsed cores of giant stars. The source of the new FRB remains a mystery, but scientists think it could emanate from a radio pulsar or magnetar, which are neutron stars. It is currently the longest-lasting FRB with the clearest periodic pattern detected to date. Researchers from MIT and McGill University in Canada, who published a study on the signal, have named it FRB 20191221A. The signal came from a distant galaxy, several billion light-years from Earth. Photo courtesy of CHIME, with background edited by MIT News Pictured is the large radio telescope CHIME that picked up the FRB. Named FRB 20191221A, this fast radio burst, or FRB, is currently the longest-lasting FRB, with the clearest periodic pattern, detected to date. ![]() This is the first time the signal itself is periodic." Astronomers detected a persistent radio signal from a far-off galaxy that appears to flash with surprising regularity. "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. "It was unusual," said Daniele Michilli, a postdoc in MIT's Kavli Institute for Astrophysics and Space Research.
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