A new radio signal from deep space once again challenges our understanding of these mysterious phenomena. This new fast radio burst, named FRB 20191221A, is not only another extremely rare repeater, but it's not even that fast. Radio flashes received in intergalactic space last three seconds, about 1000 times longer than average.
However, within this three-second time frame is a cluster of signals, with higher-intensity bursts of radiation occurring every 0,2 seconds, never before observed in a fast radio burst.
CHIME detector, picked up the signal in December 2019, and researchers quickly realized they were onto something rather strange.
"It was a rare thing," said astrophysicist Daniele Michilli of MIT's Kavli Institute for Astrophysics and Space Studies.
“Not only was it very long, lasting about three seconds, but there were remarkably precise periodic peaks that radiated like a heartbeat in every fraction of a second – boom, boom, boom. This is a situation where the signal itself is periodic.”
Fast radio bursts are one of today's most fascinating cosmic mysteries. These are extremely powerful bursts of radiation at radio wavelengths that shine through intergalactic space in a very short time span – usually within milliseconds. In that short time, the explosion radiates as much energy as 500 million Suns.
Most fast radio bursts only flash once and have not been heard since. It is impossible to predict them; to detect one, we should hope that this will happen when we have a radio telescope pointed in the right direction (although projects like CHIME with a wide field of view are very helpful in this regard). These are the most common type of FRB.
Much more rarely, repeated signals are received from a single point in the sky. These are fast repetitive radio bursts. Because they repeat, scientists can point a telescope at the sky and study the signals in much greater detail.
However, it is unclear whether the same mechanism is responsible for all fast radio bursts.
They can differ in intensity, wavelength, polarization and distribution. A fast radio burst contains an important clue. This was a fast radio burst from inside the Milky Way for the first time in 2020.
It was traced back to a type of neutron star called a magnetar. This suggested that highly magnetized, ultra-dense objects might be responsible for at least some fast radio bursts.
“CHIME has now detected many FRBs with different properties. We have seen some living in very turbulent clouds, while others seem to be in clean environments. From the properties of this new signal, we can say that there is a cloud of plasma that should be around this source, and it is extremely turbulent.”
As for what happened, the signs still point to some kind of neutron star (sorry, still no aliens).
The collapsed cores of giant stars that have expired and ejected most of their material into space are known as neutron stars. The core collapses into an enormously dense object about 20 kilometers (12 mi) wide and an estimated 2,3 times the mass of the Sun because it is no longer supported by the outward pressure of fusion.
A form of neutron star known as a magnetar has an extremely strong magnetic field. As a result of the inward and outward pull of the magnetic field, large earthquakes occur from time to time in magnetars.
Neutron stars, called pulsars, emit radio emission beams that appear to be pulsating as they spin from their poles at milliseconds. When Michilli and colleagues studied the eruptions from FRB 20191221A, they discovered features shared with pulsar and magnetar emission.
The only problem is that while the exact distance of FRB 20191221A is unknown, it may have originated from another galaxy as its explosion is almost a million times brighter than magnetars and pulsars in our own galaxy.
According to Michilli, there aren't many objects in the universe that emit strictly periodic signals. “Examples of rotating objects that emit beams of light like a lighthouse are radio pulsars and magnetars that we know in our own galaxy. We also believe this new signal could be an advanced magnetar or pulsar.”
To determine where FRB 20191221A came from and what could be causing it, the team hopes to catch more blasts from the mysterious source. This could ultimately help us understand neutron stars.
"This detection raises the question of what could be causing this extreme signal that we have never seen before and how we can use this signal to study the Universe," Michilli said. Said. "The telescopes of the future promise to discover thousands of FRBs per month, and at this point we can find most of these periodic signals."