CHIME radio telescope in British Columbia, Canada, discovers up to 10 fast radio bursts per day
Between Christmas Day 2018 and New Year’s Day 2019, Columbia University’s astrophysicist Brian Metzelger realized that he had clues to one of the most stubborn mysteries in astronomy.
He tried to track down after discovering the clues, worrying that a little mistake would ruin all the results, or that others would put together the reasonable parts first. Metzerger said: “I am racing against time, because other people may see this.”
Metzeger and other researchers around the world have brainstormed over the past few years to study the mystery of fast radio bursts. Fast radio bursts are violent and unexplained millisecond long radio signals that suddenly appear in the sky and briefly overtake the radio pulses in our galaxy—although they are farther away from us than the pulsars in the Milky Way. Millions times.
Before 2013, many astrophysicists wondered if they really existed. In the years that followed, the researchers published many explanations for the causes of rapid radio bursts. There are 48 different theories in just one statistical directory, and the theoretical number has recently exceeded the number of events itself.
The fast radio storm theory consists of two parts, similar to the “suspects” and “weapons” in a cosmic puzzle of the universe. The “suspect” is an astrophysical beast that can release enormous energy. “Weapons” can turn this energy into a troublesome, unusual radio signal.
A fast radio storm may be the result of a neutron star merger.
Now, Metzerger and his colleagues have rebuilt the “crime” scene. Earlier in March, they posted a paper on the website arxiv.org that outlines how fast radio bursts can occur when space and magnetic clouds explode in space.
This model does not require the use of magnetic stars as a source of explosion, which makes it easy to model. The magnetic star is a young neutron star that sometimes emits charged particles like the particles in the corona. Every new explosion is substituted into the surrounding clutter. When an explosion occurs, a shock wave is generated. This shock wave is observed by a corner of the universe with a brief, laser-like radio wave flash.
What astronomers really care about is that Metzerger’s theory makes very specific predictions for the future form of fast radio storms, and these predictions will soon be used for testing. A new Canadian radio telescope, called CHIME, is expected to be fully operational in late 2019 and is expected to find 1 to 10 fast radio bursts per day.
During the initial test in the summer of 2018, it discovered 13 radio bursts and the results were released in January 2019. “I think that we will be able to test this well in the next year or so,” said Shirish Tengdenkar, an astrophysicist at McGill University and a member of the CHIME Rapid Radio Attack Team.
“murderer” neutron star
The theory published by Metzeger and his colleagues Ben Margarit and Lorenzo Hiloli is based on the biggest breakthrough in the case of fast radio bursts to date.
In 2016, at the Max Planck Institute for Radio Astronomy in Bonn, Germany, a team led by Laura Spitler published their results based on the first recurring rapid radio storm in history.
Previously, the observed radioactive activity was one-off. Astronomers cannot track their position in the sky. But this radiostorm broke out again after an unpredictable time interval.
Radio astronomers quickly positioned its origins in a small, deformed dwarf galaxies. They tried to dig out clues from these radio signals and finally found that it came from dense plasma areas held by extreme magnetic fields.
The researchers also found that radio bursts were weaker, but surrounded by uninterrupted radio light. In November 2018, astronomer Jason Heathers (with Spitzer and others) discovered something weird: every moment an electric burst broke out, it actually contained some sub-bursts. The high frequency drops to the low frequency.
In the 1950s, physicists used nuclear bombs to estimate their equivalents. In these models, the shock wave front produced by a nuclear explosion squeezes more gas as it expands outward. The radiation released from the shock wave front moves downward in frequency.
Metzerger has always believed that this shock wave effect may answer the clues of the fast radio burst frequency. Then, the CHIME telescope observed another recurring event in early January. This repeated radio signal shows the same, downward frequency change.
Brian Metzger and his wife, Stasi Thomas, at the 2009 “Breakthrough Awards” awards ceremony. Brian Metzger won the New Vision Award in Physics
Now, Metzerger, Margaret and Hillory have released their complete theoretical models. Imagine a city-sized neutron star that was forged in a supernova explosion only a few years or decades ago, and its surface is constantly changing. This young magnetite occasionally emits flares that eject electrons, positrons, and heavier ions near the speed of light.
When these things are ejected, it encounters the old particles that were previously produced in the flare. When a new jet encounters old debris, its internal magnetic field instability is exacerbated. When the shock wave is squeezed outward, the internal electrons rotate along the magnetic field lines, and the motion produces a burst of radio waves. As the shock slows, the signal transitions from a higher frequency to a lower frequency.
Waiting for “judgement”
Metzerger’s model predicts some of the specific properties of future fast radio bursts. For example: all future fast radio bursts should follow the same frequency downwards. They may show the presence of gamma rays or X-rays, something that astronomers such as Spitler are already looking for.
They should be found in galaxies that form large numbers of new stars and produce new magnetic stars. When they reappear, they should pause after astronomers observe a major flash.
Metzerger’s model now faces the challenge of other viable theoretical models. Rapid radio bursts may be the result of the merger of neutron stars, and the neutron star merger in 2017 was first observed by both telescopes and gravitational wave detectors. Neutron stars may also crash into black holes when they hit other objects (such as black holes or white dwarfs), or create a fast radio storm when their magnetic lines of force are blown away by strong plasma winds.
In the past five months, although CHIME has just entered the commissioning phase, the researchers have discovered more radio storms that have not yet been released. Team members hope to begin formal observation in April. Other large radio telescopes will also be put into use. This will bring more data.
After years of lack of data and “daydreaming”, the rapid radio storm now has the possibility to unravel the mystery. In mid-February, astronomers met in Amsterdam to share the latest discoveries and discuss whether neutron stars are the ultimate cause of radio storms.
“This is a perfect point in time.” The researchers debated the Marchegel model proposed by Margaret at the meeting, but did not acknowledge the results. “We are on the verge of convergence,” said Tenden Carl. “Let’s talk about it first.”