Astronomers are at a loss about an unusual phenomenon
Fast radio bursts, or bright flashes of radio waves in space lasting milliseconds, are considered one of the most enduring mysteries of the cosmos – and now they have become a little more strange.
The first fast radio burst (FRB) was discovered in 2007, and since then hundreds of such fast and intense events have been detected emanating from distant points throughout the universe. According to previous research, flares can generate as much energy in a thousandth of a second as the Sun produces in one year or more. But as CNN reports, astronomers don't understand what causes them.
Now scientists have noticed a never-before-seen bizarre pattern in a newly discovered repeating fast radio burst called FRB 20220912A. The study, published Wednesday in the Royal Astronomical Society's Monthly Notices, details the discovery, which provides valuable clues to researchers seeking to determine the source of the phenomenon, while presenting new mysteries to unravel.
Astronomers discovered the flare using the Allen Telescope Array. or ATA, based at the California SETI Institute, which includes 42 antennas at the Hat Creek Radio Observatory in the Cascade Mountains. The team detected 35 fast radio bursts from a single source over a two-month period.
Many fast radio bursts emit radio waves lasting no more than a few milliseconds before disappearing, making fast radio bursts difficult to observe. But some radio bursts are known to repeat and release subsequent bursts, which have allowed astronomers to trace the signals to distant galaxies.
At first, FRB 20220912A appeared similar to other known “relays,” with each packet detected shifting from higher to lower frequencies. But a closer look at the signal revealed something new: a noticeable drop in the center frequency of the bursts, acting like a “skyslide whistling.” The decline became even more apparent when the researchers converted the signals into sounds using notes on a xylophone. High notes correspond to the beginning of bursts, and low notes act as ending tones.
The team tried to determine whether there was a pattern in the time between each burst, similar to some other known repeating fast radio bursts. But the researchers were unable to detect one for FRB 20220912A, further indicating that celestial events can also be unpredictable.
“This work is interesting because it provides both confirmation of the known properties of FRBs and and the discovery of some new”, – Lead study author Dr. Sophia Sheikh, a National Science Foundation MPS-Ascend postdoctoral fellow at the SETI Institute, said in a statement.
Each observation of fast radio bursts brings insights as well as new questions, researchers say.
Astronomers suspect that some fast radio bursts may come from magnetars, the highly magnetized cores of dead stars. But other studies have suggested that collisions between dense neutron stars or dead stars called white dwarfs may be the cause.
“We narrow the sources of FRBs to extreme objects such as magnetars, but no existing model can explain all the properties that have been observed so far”, – says Sophia Sheikh.
The study was the first to detect fast radio bursts using the Allen telescope array, which has been undergoing upgrades in the past few years, CNN notes. Ongoing updates to the array will allow astronomers to not only track how fast radio bursts behave at different frequencies, but also look for weaker signals.
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