Astronomers capture Intergalactic Gamma Ray Burst

Astronomers capture Intergalactic Gamma Ray Burst

An international team of astronomers led by Eleanora Troja of the University of Maryland caught a massive star as it died with an immense explosion deep in space.

The blast created a flash of visible light that 31 astronomers from the University of Maryland and Arizona State University and other institutions caught on 25th of June last year, at 6 p.m. ET.

The astronomers estimated that the blast released in just 40 seconds as much energy as a normal Sun releases over the span of its entire life. All of that energy was focused into a tight beam of gamma rays that were aimed coincidentally toward our planet.

Nathaniel Butler, an associate professor in ASU’s School of Earth & Space Exploration, said, “These are the brightest explosions in the universe School of Earth and Space Exploration. And we were able to measure this one's development and decay almost from the initial blast.”

Last year’s gamma-ray blast was caught by the astronomers with the help of two NASA satellites, viz. the Fermi Gamma-ray Space Telescope and the Swift Gamma-Ray Burst Mission, which keep an eye on the sky for such events.

The research paper further informed....

Quick reflexes

The gamma-ray blast on June 25, 2016, was detected by two NASA satellites that monitor the sky for such events, the Fermi Gamma-ray Space Telescope and the Swift Gamma-Ray Burst Mission.

The satellite observatories detected the burst of gamma rays, identified where in the sky it came from, and sent its celestial position within seconds to automated telescopes on the ground.

The MASTER-IRC telescope at the Teide Observatory in the Canary Islands observed it first, within a minute of the satellite notification. The telescope is part of Russia's MASTER network of robotic telescopes at the Teide Observatory. It made optical light observations while the initial phase was still active, gathering data on the amount of polarized optical light relative to the total light produced.

After the Sun set over this facility eight and a half hours later, the RATIR camera in which ASU is involved began observing. RATIR stands for Reionization And Transients InfraRed camera; it is mounted on a 1.5-meter (60-inch) robotically controlled telescope located on San Pedro Mártir Peak, at Mexico's National Astronomical Observatory in Baja California. Butler is the principal investigator for the fully-automated camera.

Mystery beams of energy

While gamma-ray bursters have been known for about fifty years, astronomers are still mostly in the dark about how they erupt.

"Despite a long history of observations," Butler says, "the emission mechanism driving gamma-ray bursters remains largely mysterious."

Gamma-ray bursts are detected approximately once per day and are brief, but intense, flashes of gamma radiation. They come from all different directions in the sky, and they last from tens of milliseconds to about a minute, making it hard to observe them in detail.

Astronomers believe most of these explosions are associated with supernovas. These occur when a massive star reaches the end of its normal existence and blows up in a colossal explosion. A supernova throws off some of the star's outer layers, while its core and remaining layers collapse in a few seconds into a neutron star or, in the case of highly massive stars, a black hole.

Continued RATIR observations over weeks following the June 2016 outburst showed that the gamma rays were shot out in a beam about two degrees wide, or roughly four times the apparent size of the Moon. It was sheer chance that Earth happened to lie within the beam.

Beaming effects, Butler says, may result from the spin of the black hole produced after the supernova explosion, as it releases material along its poles.

Magnetic focus

"We think the gamma-ray emission is due to highly energetic electrons, propelled outward like a fireball," Butler says. Magnetic fields must also be present, he adds, and theories differ as to how the fields are produced and to what extent the flow of magnetic energy outward is important.

A key diagnostic is measuring the radiation's polarization, he explains. This, astronomers think, is largely controlled by the strength of the magnetic fields that focus the radiation. Butler says, "Measuring the strength of magnetic fields by their polarization effects can tell us about the mechanisms that accelerate particles such as electrons up to very high energies and cause them to radiate at gamma-ray energies."

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