The cause of these mysterious millisecond radio explosions in space has escaped scientists since the phenomena were discovered in 2007. Considering how fast they ignite, these explosions, sometimes called FRBs, are very difficult to track and study.
Learning more about the origin of these bright intense radio explosions could help scientists understand what is causing them.
An international team of astronomers was able to track the locations of eight fast radio explosions. While the origins of three remain inconclusive, the researchers used Hubble’s deep-space imaging to indicate the distant galaxies where these explosions originated, including their exact locations within the galaxies.
Five of the radio explosions came from spiral galaxies. These are the most common type of galaxy in the universe, and our own Milky Way is a kind of spiral galaxy.
One feature of these galaxies is that they have spiral arms where star formation occurs.
The radio explosions they tracked were located along the arms of different spiral galaxies that range from about 400 million to 9 billion light-years away.
These explosions may be short-lived, but each creates more energy than our sun for an entire year. Scientists have discovered up to a thousand such explosions since 2007, but they have been able to track only about 15 of them. These 15 have been found to originate from distant, young, and massive galaxies.
Tracking mysterious explosions through space
A combination of visible light, ultraviolet and near-infrared imaging helped astronomers track the FRBs mentioned in the new study.
“This is the first high-resolution population of FRB,” said 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 still forming stars. The imaging allows us to get a better idea of the overall host galaxy features, such as its mass and star formation, and also to investigate what is happening right at the FRB position.”
The researchers were surprised to discover that the explosions 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, an assistant professor of physics and astronomy at Weinberg University’s Northwestern University of Arts and Sciences. in Illinois. “Because spiral arms are signs of star birth, this was a surprise, offering important evidence that FRB must correlate with star formation.”
Fong said Hubble is so sensitive that it discovers things undetectable by ground-based images. The telescope helped researchers actually confirm the presence of spiral arms or previously unseen spiral structures within the galaxies.
“Overall, the brightest regions along the spiral arms contain the youngest, most massive stars,” Fong said. “As you move away from the spiral arms, you begin to encounter older stars that don’t glow so brightly. So where FRBs are found in relation to these spiral features offers important clues as to the kind of ancestor that caused them.”
These findings indicate that the radio bursts originate from a kind of Goldilocks average, which means that the stars that could be involved in the creation of the explosions cannot be too young or too old.
Previously, scientists speculated that the origin of FRBs could be due to explosions of young stars or fusions of neutron stars. Neutron stars are the dense nuclei that remain behind when stars explode. These are known to generate gamma-ray bursts.
However, these occur in very young young stars – something that the explosions do not seem to be related to in the new study.
Instead, the researchers suggest that magnetic explosions could be the main cause of the radio explosions. Magnetars are a kind of supermassive neutron star with magnetic fields 10 trillion times more powerful than your average magnet.
“Because of their strong magnetic fields, magnets are completely unpredictable,” Fong said. “In this case, the FRB is thought to be derived from flares of young magnetism. 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 that can emit radio light. “Our study is appropriate,” she said, with that ‘Goldilocks’ scenario.
The more radio explosions they observe, the more researchers realize how diverse they are – which could mean that different types of explosions have different origins, Mannings said.
“We don’t have high enough numbers to determine the complications of the FRB population at the moment, but doing so is an exciting prospect,” Mannings said.
With the addition of new capabilities and radio telescopes in the future, Fong and Mannings hope to track more radio explosions and find out about their host galaxies.
“We’re really on the horizon of a major discovery era,” Fong said. “Finding these localized events is an important piece for the puzzle, and a very unique puzzle piece compared to what has been done before. This is a unique contribution from Hubble.”