Astronomers Uncover an Enigmatic Cosmic Explosion

Artist's Conception of a Gamma Ray Burst

Artist’s conception of a gamma-ray burst attributable to the violent collision of two large neutron stars, following their inspiring danse macabre. Along with high-energy radiation and matter spewed out in a slim jet, the occasion is considered the Universe’s predominant manufacturing unit of heavy components, together with gold and platinum. Credit score: A. Simonnet (Sonoma State College) and Goddard Area Flight Middle

Gamma-ray bursts are probably the most intense explosions within the universe and are sometimes attributable to the collapse of stars or the collision of compact stellar remnants. Nonetheless, a current discovery has challenged this understanding, because it doesn’t match into both of those classes. Astronomers from the Niels Bohr Institute have been instrumental on this examine, which has the potential to revise present theories about these highly effective occasions.

Daniele Bjørn Malesani was finishing up a routine follow-up statement of a gamma-ray burst, named GRB 211211A, utilizing the Nordic Optical Telescope on the Canary island of La Palma. An ordinary process after having obtained the textual content message that was mechanically triggered by the spacecraft “Neil Gehrel’s Swift Observatory” which screens the sky for gamma-ray bursts.

However one thing wasn’t fairly proper…

Hubble Space Telescope View of the Location of the Gamma Ray Bursts GRB 211211A and Its Surroundings

Hubble Area Telescope view of the situation of the gamma-ray bursts GRB 211211A and its environment. The zoom-in reveals the afterglow of the burst, as noticed with the Gemini North telescope on Hawaii. The binary system inflicting the burst was possible ejected prior to now from the massive, bluish galaxy on its left. Credit score: Worldwide Gemini Observatory/NOIRLab/NSF/AURA/M. zamani; NASA/ESA

Malesani is an astronomer at Radboud College within the Netherlands and a visitor researcher on the Cosmic Daybreak Middle in Copenhagen. He expertizes in gamma-ray bursts, probably the most energetic explosions within the Universe.

However to grasp what wasn’t proper, let’s first take a look at what’s a “gamma-ray burst”:

As vibrant because the Universe itself

Gamma-ray bursts are transient and ultra-bright flashes of probably the most energetic type of mild, gamma rays. Principally detected within the very distant Universe, they often are available in two classes that are thought to come up from two totally different bodily situations:

“Lengthy” bursts sometimes final from a couple of seconds to a number of minutes however are sometimes accompanied by a longer-lasting afterglow of much less energetic mild. They’re present in probably the most star-forming areas of galaxies and are considered the results of a large star that collapses to a compact[{” attribute=””>neutron star or a Nordic Optical Telescope

The Nordic Optical Telescope on the 2400 meters high mountain top Roche de los Muchachos in La Palma. Credit: Peter Laursen (Cosmic Dawn Center)

“Short” bursts are even more fleeting, with typical durations of 1/10 to 1 second. They are often seen offset from the galactic centers, or even outside galaxies. The prevailing theory is that they are the outcome of two massive stars orbiting each other in a “binary” system. At some point, they explode as supernovae, kicking them out of their host galaxy. Eventually, however, the two objects will spiral in and merge, resulting in a gamma-ray burst.

In both cases, the energy released is mind-blowing: At their peak, they can shine as brightly as all the stars in the observable Universe combined (assuming that they emit light equally in all directions; in reality, they are likely somewhat less bright but emit most of their light in narrow jets, where we just happen to lie in this direction).

The enigmatic gamma-ray bursts

Gamma-ray bursts were first discovered in 1967 by the Vela satellite, built to monitor the sky for possible tests of nuclear weapons, which would be a violation of the 1963 Nuclear Test Ban Treaty. First thought to originate from nearby sources within our own galaxy, more sensitive space observatories revealed, in the 1990s, that they must come from far outside the

Gamma-ray bursts come in two versions, “short” and “long”, which have, until now, been thought to arise from two different physical mechanisms, namely the merging of two compact objects, and the collapse of a massive star, respectively. With the new observations, this theory is now being challenged.

Mixed signals

So what was the issue with Malesani’s burst, GRB 211211A? Well, it seemed to fit in neither, or perhaps both, of these categories. “The observations showed that the burst originated outside of a galaxy typical for hosting short bursts. But rather than being a millisecond or a few seconds, this beast lasted for almost a minute,” Malesani says.

The peculiar event prompted an international team of astronomers, led by Jillian Rastinejad of

Luca Izzo, an astronomer at the DARK research section at the Niels Bohr Institute, participated in the study. He comments: “Gamma-ray bursts can show a variety of behaviors, but the distinction between long and short events has been clearly established since the 1990s and is considered one of the pillars in the field. This finding caught us really by surprise.”

A new engine for making gold?

Kilonovae are thought to be the main mechanism for creating heavy elements such as the precious silver, gold, and platinum, the radioactive plutonium and uranium, as well as many others. As always in physics, definite proof that a kilonova is responsible for the long gamma-ray burst does not exist.

When the astronomers nevertheless are confident in their interpretation, it is due to several circumstances. Johan Fynbo, professor at the Cosmic Dawn Center and partaker in the study, explains:

“The afterglow of the burst showed colors and features that are consistent with a kilonova, and which haven’t been seen for any other types of objects. Moreover, we would not expect to see a collapsing star outside of a galaxy, since traveling this far takes hundreds of millions of years, while massive stars collapse on timescales less than 10 million years.”

But in principle, GRB 211211A could be a collapsar inside a faint or dusty, undetected galaxy, although the Hubble images are indeed very deep and ought to have seen this. “Follow-up observations with the more sensitive

Future observations of more long bursts from kilonovae will teach us more about this exciting phenomenon. 

Reference: “A kilonova following a long-duration gamma-ray burst at 350 Mpc” by Jillian C. Rastinejad, Benjamin P. Gompertz, Andrew J. Levan, Wen-fai Fong, Matt Nicholl, Gavin P. Lamb, Daniele B. Malesani, Anya E. Nugent, Samantha R. Oates, Nial R. Tanvir, Antonio de Ugarte Postigo, Charles D. Kilpatrick, Christopher J. Moore, Brian D. Metzger, Maria Edvige Ravasio, Andrea Rossi, Genevieve Schroeder, Jacob Jencson, David J. Sand, Nathan Smith, José Feliciano Agüí Fernández, Edo Berger, Peter K. Blanchard, Ryan Chornock, Bethany E. Cobb, Massimiliano De Pasquale, Johan P. U. Fynbo, Luca Izzo, D. Alexander Kann, Tanmoy Laskar, Ester Marini, Kerry Paterson, Alicia Rouco Escorial, Huei M. Sears and Christina C. Thöne, 7 December 2022, Nature.
DOI: 10.1038/s41586-022-05390-w

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