Cosmic radio bursts discovered in an amazing place in space, Gütsel Online

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Astronomers have been surprised by the source of mysterious bursts of radio emission in the sky, called “Fast Radio Bursts”, at the closest distance from Earth.

Effelsberg radio observatory with a 100-meter MPiFR radio telescope. The telescope was used simultaneously for observations of pulsars with the PSRIX data recording system and for VLBI observations as part of the EVN network of radio telescopes. Photo: Norbert Thacken, MPIfR

Cosmic radio bursts seen in an unexpected place in space

Astronomers have been surprised by the source of mysterious bursts of radio emission in the sky, called “Fast Radio Bursts”, at the closest distance from Earth. Precise measurements using radio telescopes showed that the flares occurred in a globular cluster, a system of old stars, and in a way that no one expected. Originating in the neighboring spiral galaxy M 81, it is the closest source to Earth #radio flashing submit.

The results of an international team of scientists, including Ramesh Karuppusami and Uwe Bach from MPIfR Bonn, will be presented this week in two dedicated publications.

Fast radio bursts (or FRBs) are unpredictable, extremely short bursts of light from space. Since its discovery in 2007, astronomers have struggled to understand it. So far, they have only been detected using radio telescopes in the radio part of the spectrum.

Each of these radio bursts lasts only about a thousandth of a second. However, each flash emits as much energy as the sun emits in a whole day. Hundreds of such radio bursts occur every day and are already visible across the sky. Most of them are located far from Earth, in galaxies that are billions of light years away from us.

In two papers published in parallel this week in the journals Nature and Nature Astronomy, an international team of astronomers present observations that bring scientists one step closer to solving the mystery – and at the same time raise new mysteries. The group is led by Franz Kirsten (Chalmers University, Sweden and ASTRON, the Netherlands) and Kenzi Nimmo (ASTRON and the University of Amsterdam).

Scientists set out to make high-precision measurements of a repeating lightning source discovered in January 2020 in the constellation Ursa Major.

“We wanted to find clues as to the origin of the outbreaks. By using several radio telescopes in tandem, we can locate a source in the sky with the utmost precision. This gives us the opportunity to determine what the local environment of a fast radio burst looks like,” says Franz Kirsten.

Close but surprising position

Analyzing their measurements, the astronomers found that the repeated radio bursts were coming from a place no one expected. They tracked the flares to the outskirts of the nearby spiral galaxy Messier 81 (M 81), about 12 million light-years away. This discovery represents the closest source of fast bursts of radio emission. There was another surprise. The position coincided exactly with a globular cluster, a dense cluster of very old stars.

“It is amazing to find fast bursts of radio emission in a globular cluster. It’s a place in space where only old stars can be found. Far out in the universe, such flares have been found in places where the stars are much younger,” says Kenzie Nimmo.

“The similarity of the explosion to the radiation of some pulsars in our galaxy brings us into familiar territory, but also makes it clear that the precursors of the explosion can be very different. This is certainly an incentive to detect and describe more of these radio bursts,” adds study co-author Ramesh Karuppusami (Max Planck Institute for Radio Astronomy, MPIfR).

Many fast bursts of radio emission have been detected around young massive stars much larger than the Sun. In these places, stellar explosions often occur, leaving behind highly magnetized remnants.

A number of scientists have concluded that fast radio bursts may come from objects known as magnetars. Magnetars are the extremely dense remnants of exploded stars that are the strongest known magnets in the universe.

“We expect magnetars to be bright and young objects and definitely not from the environment of old stars. So if what we’re seeing is indeed a magnetar, it couldn’t have been created by the explosion of a young star. There must be another way,” says Jason Hessels (University of Amsterdam and ASTRON), member of the research team.

Scientists believe the source of the radio bursts is something that has been predicted but never seen before: a magnetar that formed when a white dwarf built up enough mass to collapse under its own weight.

“Strange things happen over billions of years of life in a tight star cluster. We believe we are seeing a star with an unusual history here,” says Franz Kirsten.

Ordinary stars like the Sun age over time and turn into small, dense, bright objects called white dwarfs. Many stars in a star cluster live together in binary star systems. Of the tens of thousands of stars in the cluster, some come so close that one star picks up material from another. “This could lead to a scenario known by the technical term “accretion-driven collapse,” explains Kirsten.

“If one of the white dwarfs gains enough extra mass from its companion, it can turn into an even denser star, the so-called neutron star. This is a rare event, but in a cluster of old stars, it would be the easiest way to generate fast bursts of radio emission,” says McGill team member Mohit Bhardwaj. #University In Canada.

The fastest

Looking for more clues, by increasing the amount of data, astronomers found another surprise: some of the outbursts were even shorter than they expected.

“Radio bursts changed the brightness in just a few tens of nanoseconds. This tells us that they must come from a tiny volume in space, smaller than a football field and maybe only a few tens of meters across,” says Kenzie Nimmo.

Similar ultrashort signals have also been observed from one of the most famous celestial objects, the pulsar in the Crab Nebula. It is the tiny, dense remnant of a supernova explosion seen from Earth in 1054 AD in the constellation Taurus. Both magnetars and pulsars are different types of neutron stars and are therefore extremely dense objects with the mass of the sun in a city-sized volume that have strong magnetic fields.

“Some of the signals we measured are short and extremely strong, as are some of the signals from the Krebs pulsar. This suggests that we are indeed seeing a magnetar, albeit in a place where magnetars have not been found before,” says Kenzie Nimmo.

Future observations of this and other systems will help determine whether the source is actually an unusual magnetar or something else, such as a pulsar with unusual properties, or a black hole and a dense star in a close orbit.

“These rapid bursts of radio emission seem to be giving us new and unexpected insights into stellar life and death. If true, they could, like supernovae, tell us something about stars and their lives that applies to the entire universe,” says Franz Kirsten.

the following information

To study the source with the highest possible resolution and sensitivity, the scientists combined telescopic measurements within the European VLBI Network (EVN). By combining data from 12 parabolic antennas located on the other side of the world (Sweden, Latvia, the Netherlands, Russia, Germany, Poland, Italy and China), they were able to determine exactly where in the sky the radio burst originated.

The 100-meter radio telescope MPIfR, the most sensitive single telescope in Europe, was used in two ways: on the one hand, as part of the EVN network, on the other hand, it provided high-temporal resolution pulsar data with PSRIX data. recording system.

»I am always delighted when data from Effelsberg can contribute to such a remarkable result. The involvement of our 100-meter telescope can be decisive, especially for VLBI observations of weak signals,” says Uwe Bach from MPIfR, co-author and responsible VLBI expert at the Effelsberg Radio Observatory.

The EVN measurements were supplemented by data from several other radio telescopes, including the Carl G. Jansky Very Large Array (VLA) in New Mexico, USA.

original publication

F. Kirsten et al., “Repeating source of fast radio bursts in a globular cluster”, “Nature”, 2022, DOI 10.1038/s41586-021-04354-w,

C. Nimmo and Altera, “Burst and Luminosity Timescales Link Young Pulsars and Fast Radio Bursts”, Natural Astronomy, 2022, DOI 10.1038/s41550-021-01569-9,

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