Astronomers ponder "mystery" over radio wave eruptions

Astronomers ponder “mystery” over radio wave eruptions

Powerful eruptions of radio waves from a distant dwarf galaxy discovered using a massive telescope in China are moving scientists closer to solving what was called a “cosmic mystery” that has lingered for several years.

Since their discovery in 2007, astronomers have struggled to understand what causes phenomena called rapid radio bursts involving pulses of radio-frequency electromagnetic radiation emanating from places inside our Milky Way and other galaxies.

Radio waves have the longest wavelengths in the electromagnetic spectrum.

Astronomers suspect that these eruptions may be triggered by certain extreme objects. These may include: a neutron star, the compact collapsed nucleus of a massive star that exploded like a supernova at the end of its life cycle; a magnetar, a type of neutron star with an ultra-strong magnetic field; and a black hole that messily eats a nearby star.

Scientists said they discovered a fast-moving radioburst, or FRB, coming from a dwarf galaxy nearly three billion light-years from Earth. A light year is the distance light travels in a year – 5.9 trillion miles (9.5 trillion km).

FRB was first seen in 2019 using the FAST telescope in Guizhou Province in China, the world’s largest radio telescope with a bowl, which has a signal reception area equivalent to 30 football pitches. It was further studied with the VLA telescope in New Mexico.

“We still call fast radio explosions a cosmic mystery, and rightly so,” said astrophysicist Di Li of the Chinese Academy of Sciences in Beijing, the FAST chief researcher and co-author of the research published in the journal Nature.

“Fast radio bursts are intense, short flashes of radio light that are powerful enough to be seen from across the universe,” added Caltech astronomer and co-author Casey Law.

“The storm flashes on and off in about a millisecond, much faster than a moment. Some sources to the FRB have been shown to give several bursts in what looks like storms of activity, but others have only been seen to burst once.”

The recently described FRB is a recurring one that also has a sustained but weaker radio emission between showers. In other words, it always remains “on”.

Most of the approximately 500 known FRBs are not repeated. The new one is similar to another that was discovered in 2016 and which was the first FRB whose place was determined.

Li noted that many hypotheses have been put forward to try to explain these outbursts.

“The abundance of models reflects our lack of understanding of FRBs. Our work favors active repeaters born from an extremely explosive event like a supernova. These active repeaters are also young, as they must be seen not long after the birth event,” Mr Li said.

Astronomers suspect that the recently described FRB is a “newborn”, still surrounded by dense material blown into space by a supernova explosion that left behind a neutron star. They said that repeated outbreaks may be a feature of younger FRBs, which may disappear over time.

Discoveries such as the recently described FRB can help researchers determine the cause of these radio bursts.

Scientists were previously able to create an explanation for the cause of another enigmatic phenomenon – enormously energetic explosions called gamma-ray bursts – which resulted from the death of massive stars, fused neutron stars and magnetars.

“FRBs have risen rapidly to become a wonderful example of an astrophysical puzzle, just as gamma-ray bursts were a few decades ago,” Law said.

“We know more and more about the phenomenon, where the sources live, how often they burst, etc. But we are still hunting for that golden measurement that will give us a definitive answer as to what causes them.”


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