They trace mysterious fast radio bursts to the arms of spiral galaxies

(CNN) – Scientists have traced the location of multiple fast radio bursts to their origins with the help of the Hubble Space Telescope, and it is not what they expected.

The cause of these mysterious millisecond-long radio bursts in space has remained hidden from scientists since the phenomenon was discovered in 2007. Given the speed with which they explode, these explosions, sometimes called FRBs, are very difficult to detect. go on and study.

Knowing more about the origin of these bright, intense radio bursts could help scientists understand what causes them.

An international team of astronomers was able to track the location of eight fast radio bursts. Although the origin of three of them remains inconclusive, the researchers used Hubble’s deep space images to pinpoint the distant galaxies from which these outbursts originated, including their exact location within the galaxies.

The study has been accepted and will be published soon in The Astrophysical Journal.

Five of the radio bursts came from spiral galaxies. These are the most common type of galaxy in the entire universe, and our own Milky Way is a type of spiral galaxy.

A characteristic of these galaxies is that they have spiral arms where star formation occurs.

The radio bursts they tracked were located along the arms of different spiral galaxies that are between 400 million and 9 billion light years apart.

These bursts may be brief, but each one of them generates more energy than our sun over the course of an entire year. Scientists have discovered up to a thousand such bursts since 2007, but have only been able to track about 15 of them. Those 15 originated in distant, young and massive galaxies.

Tracking mysterious bursts in space

A combination of images in visible, ultraviolet and near-infrared light helped astronomers track the FRBs mentioned in the new study.

“This is the first high-resolution view of an FRB population,” says study lead author Alexandra Mannings, a graduate student in astronomy and astrophysics at the University of California, Santa Cruz. ‘Most galaxies are massive, relatively young and are still forming stars. The images allow us to get a better idea of ​​the general properties of the host galaxy, such as its mass and rate of star formation, as well as to probe what is happening right at the FRB’s position. ‘

The researchers were surprised to find that the bursts originated from the spiral arms.

“We don’t know what causes FRBs, so it’s really important to use context when we have it,” said study co-author Wen-fai Fong, assistant professor of physics and astronomy at Northwestern University’s Weinberg College of Arts and Sciences. , in Illinois.

“Since spiral arms are signs of star birth, this was a surprise, offering an important clue that FRBs must correlate with star formation.”

Hubble is so sensitive that it discovers things that cannot be detected using Earth images, Fong said. The telescope helped researchers actually confirm the presence of previously unseen spiral arms or spiral structures within galaxies.

“Generally, the brightest regions along the spiral arms contain the youngest and most massive stars,” Fong said. “As you move away from the spiral arms, you start to find older stars that don’t shine as bright. So the location of FRBs with respect to these spiral features offers important clues about the type of parent that causes them. ‘

These findings indicate that the radio bursts originate in a kind of “middle ground,” meaning that the stars that might be involved in creating the bursts cannot be too young or too old.

Previously, scientists have speculated that the origin of FRBs could be due to explosions of young stars or mergers of neutron stars. Neutron stars are the dense cores that remain after the explosion of stars. These are known to generate gamma ray bursts.

However, these occur in young and very massive stars, which does not appear to be related to the bursts in the new study.

Instead, the researchers suggest that magnetar explosions could be the dominant cause of radio bursts. Magnetars are a type of supermassive neutron star with magnetic fields 10 trillion times stronger than a normal magnet.

Observing a fast radio burst in our Milky Way last year it came from a region where there is a magnetar.

“Due to their strong magnetic fields, magnetars are quite unpredictable,” explained Fong. “In this case, the FRBs are believed to come from flares from a young magnetar. Massive stars undergo stellar evolution and become neutron stars, some of which can be strongly magnetized, leading to flares and magnetic processes on their surfaces, which can emit radio light. Our study fits, ”he said, with that“ fair-minded ”scenario.

As more radio bursts are observed, researchers become aware of their diversity, which could mean that different types of bursts have different origins, Mannings said.

“At the moment, we don’t have enough figures to determine the ins and outs of the FRB population, but doing this is an exciting prospect,” Mannings said.

It’s known that some radio bursts repeat, and Mannings wants to determine if there are notable differences between galaxies that host repeating radio bursts and the occurrences of single burst events.

With the addition of new capabilities and radio telescopes in the future, Fong and Mannings hope to track more radio bursts and learn about their host galaxies.

“We are really on the horizon of an important era of discovery,” said Fong. “Finding these localized events is an important piece of the puzzle, and a very unique piece of the puzzle compared to what has been done before. It’s a unique contribution from Hubble. ‘