Not Alone? Four “Mysterious Signals” Captured From Outer Space
A team of scientists headed by Shivani Bhandari, an astronomer with the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia’s federal agency responsible for scientific research, has made a breakthrough discovery by pinpointing the precise location of four fast radio bursts (FRBs).
FRBs are very mysterious bursts of radio waves coming from somewhere in the universe. The average pulse ranges for a few milliseconds, caused by high-energy sources, which are not entirely understood.
CSIRO’s ASKAP radio telescope in Western Australia detecting FRBs. h/t CSIRO
Bhandari’s new research, published on June 1 in The Astrophysical Journal Letters, reveals that four FRBs came from massive galaxies forming new stars. They said FRBs originated not from the center of galaxies, but rather from the outer edges.
“These precisely localized fast radio bursts came from the outskirts of their home galaxies, removing the possibility that they have anything to do with supermassive black holes,” said Bhandari.
Bhandari’s team found exact locations for FRB 180924, FRB 181112, FRB 190102, and FRB 190608 by using the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in Western Australia.
Source of FRBs. h/t CSIRO
Bhandari said, “This first detailed study of the galaxies that host fast radio bursts rules out several of the more extreme theories put forward to explain their origins, getting us closer to knowing their true nature.”
Co-author of the study, CSIRO Professor Elaine Sadler said FRBs could not have come from a superluminous stellar explosion or cosmic strings.
“Models such as mergers of compact objects like white dwarfs or neutron stars, or flares from magnetars created by such mergers, are still looking good,” Sadler said.
Dame Jocelyn Bell Burnell, an astrophysicist from Northern Ireland who co-discovered FRBs, said:
“Positioning the sources of fast radio bursts is a huge technical achievement and moves the field on enormously. We may not yet be clear exactly what is going on, but now, at last, options are being ruled out. This is a highly significant paper, thoroughly researched, and well written,” said Burnell.
According to another paper (dated February 3) by a team of astrophysicists in Canada, a “mystery radio signal” was recorded as repeating based on a clearly discernible pattern. “The discovery of a 16.35-day periodicity in a repeating FRB source is an important clue to the nature of this object,” the team said. A summary of some of the key findings are as follows:
“Between September 16, 2018 and October 30, 2019, detected a pattern in bursts occurring every 16.35 days. Over the course of four days, the signal would release a burst or two each hour. Then, it would go silent for another 12 days.
“…The signal is a known repeating fast radio burst, FRB 180916.J0158+65. Last year, the CHIME/FRB collaboration detected the sources of eight new repeating fast radio bursts, including this signal. The repeating signal was traced to a massive spiral galaxy around 500 million light-years away.”
Both findings suggest astronomers are one step closer to understanding the source of these mysterious radio signals coming from deep within the universe. Could this mean we’re not alone?
Astronomers have detected an “activity cycle” behind massive radio pulses emanating from a galaxy billions of light-years away, shedding light on one of the great cosmic mysteries, which some suggest could be a sign of alien life.
Known as fast radio bursts (FRBs), the flashes of emissions were first noticed in 2007 and appear to originate from galaxies light-years away from Earth, but exactly what causes them still has scientists scratching their heads. The bursts are immensely powerful, giving off as much energy in the space of a few milliseconds as Earth’s sun does in a whole century.
While more than 100 FRBs have been observed since their discovery, most of them have been a one-off phenomenon, giving off only a single burst. But more recently, scientists have found that a small number of FRBs repeat, noticing regular patterns or “activity cycles” behind the enigmatic flashes
One repeating burst – FRB 121102, emitting from a small dwarf galaxy about three billion light-years away from Earth – was watched for some five years by researchers at the Jodrell Bank Observatory in England, revealing a 157-day pattern. The burst appears to flare up for 90 days, only to die down for another 67 before repeating again, according to the findings, which were recently published in the Monthly Notices of the Royal Astronomical Society journal.
Though the researchers still can’t say what’s behind the cyclic activity, a number of explanations have been put forward, some suggesting the pulses are caused by the ‘wobble’ of a rotating magnetar – or a highly magnetized neutron star – while others posit they are linked to the orbital motions of a binary star system.
Lacking a definitive natural explanation for the mystery bursts, in 2017 researchers at the Harvard-Smithsonian Center for Astrophysics decided to explore unnatural causes, conducting a study theorizing that a massive solar-powered alien radio transmitter may be sending off the bursts in order to power “interstellar light sails.” They found that such a feat would be technically possible, but would require a solar panel with an area twice the size of Earth, putting it far beyond mankind’s current abilities. Though the scientists acknowledged the work was highly speculative, they nonetheless said it was “worth contemplating” an “artificial origin” for the radio bursts, which continue to baffle astronomers.
The mystery radio bursts detected by the Parkes Observatory, seem to be coming from way beyond the Milky Way.
ALEX CHERNEY, TERRASTRO.COM/SCIENCE PHOTO LIBRARY
Astronomers have for the first time detected a population of ultrashort radio bursts with properties that strongly suggest that they originate from outside the Milky Way Galaxy. Lasting for a few thousandths of a second and estimated to erupt roughly every 10 seconds, the mysterious bursts are likely to be caused by a previously unknown class of radio-emitting phenomenon, researchers report in Science1.“This is one of the most important radio discoveries in the last couple of decades,” says Scott Ransom, an astronomer at the US National Radio Astronomy Observatory in Charlottesville, Virginia, who was not part of the study.
Although radio signals that vary over days to months have been recorded from distant galaxies for decades, ultrashort signals from beyond the Milky Way had never been definitively detected, notes study co-author Dan Thornton, an astronomer at the University of Manchester, UK. He and his colleagues embarked on a search for extragalactic radio bursts after a report in 2007 suggested that one such signal had been tentatively found2.
Using archived data from the 64-metre Parkes Radio Telescope in Australia — the same instrument that had recorded the tentative single burst — Thornton and his collaborators found four bursts that seemed to come from outside the Galaxy.
As radio waves travel through ionized material in space, they encounter a sea of electrons that slows down the lower-frequency components of the signals, but leaves higher-frequency components almost unaffected. As a result, a narrow radio signal travelling a long distance spreads out or disperses. The four radio signals found by Thornton and his team are so spread out that the distribution of electrons in the Milky Way can account for only 3–6% of their dispersion. That is a strong indication that all four signals, which come from different regions of the sky, originate outside the Galaxy. “These things look conclusively to be extragalactic,” says Ransom.
Cosmic riddle
Models of the electron content of intergalactic space suggest that the bursts crossed between 1.7 billion and 3.2 billion parsecs (between 5.5 billion and 10 billion light years) of space to reach Earth, coming from much farther away than the edge of the Milky Way.
The brevity and brightness of the bursts suggests they were emitted by some kind of small, energetic object such as a magnetar, a neutron star with an extremely powerful magnetic field. The bursts “are signalling the existence of a cataclysmic event involving large amounts of mass and or energy”, says Thornton. But their origin remains a mystery because astronomers were unable to pinpoint where the fleeting signals came from.
Researchers at Parkes are now working to find bursts in real time, so that optical telescopes can hunt for any visible light that may be given off by the same source. They could use the wavelengths of that light to calculate exactly how far away the source is.
If astronomers can pinpoint the distances, they can use the dispersion of the radio signals to measure the number of electrons in the space between galaxies. The electron abundance is representative of the amount of baryons — protons and neutrons — that resides in intergalactic space.
That number is of intense interest because it could solve a cosmic riddle: why the abundance of baryons inside galaxies falls short of the total tally that observations of the early Universe suggest should exist today. The new class of bursts could finally locate the missing baryons, notes Thornton.
The mystery radio bursts detected by the Parkes Observatory, seem to be coming from way beyond the Milky Way.
