Gamma ray bursts are the most energetic and luminous electromagnetic events since the Big Bang. It can release more energy in 10 seconds than the Sun can emit in its entire 10 billion years of expected lifetime. They are the most powerful events in the universe, detectable across billions of light-years. They are high energy explosion that occurs in space atleast once everyday. They can last from milliseconds to a minute. It isn’t possible to predict the exact time and location of its occurrences.

What are Gamma Rays ?

Gamma rays are ionizing electromagnetic radiation, obtained by the decay of an atomic nucleus. Gamma rays are  penetrating form of electromagnetic radiations and can damage living cells to a great extent. They have the smallest wavelengths and the most energy of any wave in the EV spectrum. They are produced by the hottest and most energetic objects in the universe such as neutron stars and , supernova explosions and regions around black holes. On Earth , gamma rays are generated by nuclear explosions,lightning and the less dramatic activity of radioactive decay.

Gamma ray detectors :

Gamma rays can’t be captured and reflected by mirrors like optical light and x-rays. Its wavelength is too short to pass through the space.
Gamma ray detectors contain densely packed crystal blocks. As Gamma rays pass through,  they collide with electrons in the crystal.
This process is called Compton Scattering where a gamma ray strikes an electron and loses energy. These collisions create charged particles that can be detected by the sensor.

Type of Gamma Ray Bursts :

1. Long GRBs :
• They observe long bursts in association with the demise of massive stars.
• When a star much more massive than the Sun runs out of fuel, its core suddenly collapses and forms a black hole.
• Black hole refers to a point in space where matter is so compressed as to create a gravity field from which even light cannot escape.
• As matter swirls toward the black hole, some of it escapes in the form of two powerful jets that rush outward at almost the speed of light in opposite directions.
• Astronomers only detect a GRB when one of these jets happens to point almost directly toward Earth.
• Following the burst, the disrupted star then rapidly expands as a supernova.

2. Short GRBs :
• Short GRB forms when pairs of compact objects – such as neutron stars, which also form during stellar collapse – spiral inward over billions of years and collide.
• A Neutron star comprises one of the possible evolutionary end-points of high mass stars.

GRB 200826A :

• NASA’s Fermi spotted a very short, powerful Gamma-Ray Bursts (GRBs) that lasted for about a second. It was named GRB 200826A after the date it occurred, which is 26th August 2020. It was a sharp blast of high-energy emission lasting just 0.65 seconds.
• After traveling for a very long period of time through the expanding universe, the signal had stretched out to about one-second-long when it was detected by Fermi’s Gamma-ray Burst Monitor.
• It had been racing toward Earth for nearly half the present age of the universe.
• It is considered to be the the shortest GRB till now and it is caused by the death of a massive star.
• It emitted 14 million times the energy released by entire milky way galaxy over the same amount of time , making it one of  the most energetic short duration GRBs ever seen.

Significance of GRB 200826A :
It has helped to resolve the long-standing issues related to gamma-ray bursts. Also, this study triggers to re-analyse all such known events to constrain number densities better.

Sources : PIB and Dristi IAS