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World’s largest radio telescope captures aftermath of star collisions

On Wednesday, astronomers presented us with a mysterious video: images adorned with lime-green spots moving steadily against a dark background. But right in the center of this recording, a spot is not like the others. It’s the brightest neon blob of them all, and it gets better with every frame.

What you see is evidence that about 20 billion years ago, a super-powerful neutron star collided with a fainter star, spewing out a short-lived explosive gamma-ray burst, rippling gravitational waves through the cosmos and diffusing the surrounding space with a powerful afterglow. It was a shattering merger that happened when the universe was just 40% of its current age, and our remarkable view of its incident is courtesy of the world’s largest radio telescope, the Atacama Large Millimeter/submillimeter Array located in Chile.

Specifically, ALMA is a combination of 66 radio telescopes spread across the high altitude Chilean Andes. And they work together to bring us data on the violent side of our universe.

“Afterglows for short bursts are very hard to find, so it was spectacular to see this event shine so brightly,” said Wen-fai Fong, an astronomer at Northwestern University and principal investigator of the ALMA program, in a statement. . “This startling discovery opens up a whole new area of ​​study, as it motivates us to observe many more with ALMA and other telescope arrays in the future.”

First-Ever Time-Lapse Video of Short Gamma-Ray Burst Afterglow Captured in Millimeter Wavelengths by ALMA

ALMA (ESO/NAOJ/NRAO), T. Laskar (Utah), S. Dagnello (NRAO/AUI/NSF)

Details of the findings by Fong and his fellow researchers will soon be published in an upcoming issue of The Astrophysical Journal Letters. For now, a preprint is available on arXiv.

An incomprehensible force of nature

Short-lived gamma-ray bursts, like this one officially dubbed GRB 211106A, are among the most intense and powerful explosions known to science. But unlike the longer-lived ones, they remained a mystery due to their fleeting nature, until 2005 when NASA’s Neil Gehrels Swift Observatory collected data on one for the first time.

Within seconds, these cosmic outbursts can emit more energy than our sun will emit in its entire lifetime. Although such an extreme makes sense to them, as these phenomena stem from binary star collisions that involve at least one neutron star, a hyperdense ball of gas that rivals even black holes in gravitational monstrosity.

Just one tablespoon of neutron star would equal something like the weight of Mount Everest.

A still of two neutron stars about to merge. Replace one with a normal star and you might imagine what happened long ago with the cosmic subjects of this new study.

Goddard Space Flight Center / NASA CI Laboratory

“These mergers occur because of gravitational wave radiation that removes energy from the orbits of binary stars, causing the stars to spiral towards each other,” said Tanmoy Laskar, lead author of the study and astronomer at Radboud University, in a statement. . “The resulting explosion is accompanied by jets moving at near the speed of light. When one of these jets is pointed at Earth, we observe a short pulse of gamma radiation or a short-lived GRB .”

It’s the bright green blip we see in the recording of the recent burst.

ALMA expertise

The fact that the study team used ALMA to locate this particular burst marks the first time such an event has been captured in millimeter wavelengths, the specialty of the Chilean oscilloscope.

Although this dramatic collision has already been studied with NASA’s Hubble Space Telescope, it has only been seen under the guise of optical and infrared wavelengths of light. With these wavelengths, Hubble could essentially only estimate information about the distant galaxy in which this merger occurred, but not too much about the afterglow that followed. Even if the agency’s groundbreaking James Webb Space Telescope one day embarks on a survey mission to GRB 21106A, it will also be limited to wavelengths of infrared light, but over a much broader spectrum.

ALMA, on the other hand, could see something different from what Hubble was doing with its millimeter wavelengths – it indeed captured the afterglow of GRB 21106A. And after some deliberation, the new study’s team agreed that the afterglow from this short gamma-ray burst is among the most luminescent ever seen.

World’s largest radio telescope captures aftermath of star collisions

This view shows several of the ALMA antennas and central regions of the Milky Way above.

ESO/B. Tafresh

“What makes GRB 211106A so special is that not only is it the first short-lived GRB we’ve detected in this wavelength, but also, through millimeter and radio detection, we’ve been able to measure the angle opening of the jet,” Rouco Escorial, study co-author and Northwestern University astronomer, said in a statement.

Ultimately, such information could prove essential for inferring the rates of such GRBs in our universe and comparing them to the rates of double neutron star mergers and possibly even black hole mergers.

“ALMA breaks the playing field in terms of capabilities at millimeter wavelengths and allowed us to see the faint and dynamic universe in this kind of light for the first time,” Fong said. “After a decade of observing short GRBs, it is truly amazing to see the power of using these new technologies to unwrap surprise gifts from the universe.”


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