23.01.2019 change 23.01.2019

A hot cocoon of matter around an exploding supernova

Source: amu.edu.pl Source: amu.edu.pl

Poznań astronomers working in an international team observed a gamma ray burst and an associated cocoon of heated matter. For the first time, they confirmed the association of this phenomenon with simultaneous supernova explosion.

The observations were carried out with the Roman Baranowski Telescope - a robotic instrument owned by the Adam Mickiewicz University, located in Arizona (USA) and operated remotely from Poznań via Internet connection. Research - conducted under the supervision of Dr. Michał Michałowski from the Astronomical Observatory Institute of Adam Mickiewicz University in Poznań - has been published in "Nature", the university representatives inform in a release.

"This discovery is very important because it opens up the possibilities of researching new processes related to explosions of the most massive stars. It also confirms previous theoretical predictions" - says Dr. Michał Michałowski. He adds that the results confirm the capabilities of the Baranowski Telescope.

When we look at the stars in the night sky, we do not realize that the Universe is like a minefield. Every now and then huge explosions of massive stars, called supernovae, take place. For a short time they shine as brightly as entire galaxies composed of hundreds of millions of stars. The brightest explosions in the Universe are called gamma-ray burst; they happen when the most massive stars die.

The generally accepted theoretical model of a gamma-ray burst involves three components: a narrow jet of particles (emitting radiation in various ranges of light spectrum), a hot cocoon of matter surrounding the star and light emission connected with supernova

This event resembles a combination of a bulb (supernova) and a powerful torch shining in both directions (jet). If we look at this "bulb" perpendicularly to the jet, we see the light of the supernova. If we happen to be within the narrow jet, then we are blinded by the gamma-ray burst. To complete the picture, there is also a ring of hot gas, perpendicular to the jet. That ring forms from matter expelled from a rapidly rotating core of the star.

While the connection between gamma-ray bursts and supernovae type Ic has been proved in the past, the existence of the cocoon predicted by the theoretical model was a mystery.

When a gamma-ray burst GRB 171215A exploded in a nearby galaxy 500 millions light years away on the 5th of December 2017, the team of astronomers from 13 countries started an intensive observational campaign using many telescopes around the world. This resulted in the first confirmation of the existence of the hot cocoon surrounding the exploding star and its connection with the gamma-ray burst.

"It was known that this effect should occur, but previous research groups were unable to collect data that would confirm it. We had to react quickly, we started observing the object almost immediately after the explosion" - says Dr. Michałowski.

Dr. Michałowski`s team members were: Prof. Tadeusz Michałowski, Dr. Krzysztof Kamiński, Dr. Tomasz Kwiatkowski and Mikołaj Krużyński.

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