Gamma-ray bursts are the brightest and most energy-packed explosions ever recorded in the universe, second only to the Big Bang!
Our universe is unfathomably huge and equally hostile! With massive swaths of nothingness between tangible celestial bodies, this blackness spans hundreds of billions of miles, with a handful of matter splattered unevenly throughout the vast distances.
Of course, the conditions are mostly uninhabitable, with no breathable air and a lack of the typical things that allow life to exist. This darkness gets beautifully lit up sometimes, although that doesn’t really change the hostility of the situation. These bright sources of light come from gigantic explosions as meteoroids bombard a planet, violent flares spit out of a burning star, or as quasars collide with themselves.
However, one type of cosmic explosion blows all of these out of the water. They are so deadly that we’ve spotted them billions of light-years away from our planet—Gamma-Ray Bursts.
Energy-Packed Gamma-Ray Bursts
The sun shines brightly and illuminates our daytime skies. It is the source of life on Earth as we know it, nourishing and supporting a plethora of species with the light it emits. With the constant process of fusing hydrogen into helium, the sun burns pockets of gas, creating huge solar flares. Its reach is also enormous, as its light makes its way to inconceivably distant corners of the solar system, where the distances stretch into the billions of miles. The Sun produces about 4 x 10^26 Joules of energy per second and given the Sun’s lifespan, which is 10 billion years, it does add up to quite a lot of energy being burned.
However, this doesn’t hold a candle to Gamma-Ray Bursts, as they release the same amount of energy it takes the Sun 10 billion years to produce… in just the first 10 seconds of their existence! Gamma rays are the most energetic wave in the electromagnetic spectrum and they have the smallest wavelengths. They are regarded as the most energy-packed and luminous events of the universe, second only to the Big Bang, although these bursts are short-lived, lasting anywhere from milliseconds to hours.
Gamma Rays are abundant in the universe, but invisible to the naked human eye, thus leaving our night skies black. If we could see these rays, the night sky would look very different, much more chaotic and flickery.
Causes of Gamma-Ray Bursts
Electromagnetic radiation carries radiant energy in the form of waves (photons, quanta) in an electromagnetic field. These waves have properties depending on their wavelengths, which determine their behavior; this placement and potential behavior can be mapped out in the electromagnetic spectrum. This spectrum includes radio waves, microwaves, infrared, visible light (to humans), ultraviolet, X-rays and Gamma rays, arranged in descending order of the wavelengths.
Gamma Rays, being at the end of the spectrum, arise from the radioactive decay of atomic nuclei. They have the shortest wavelengths, but pack the most energy in the spectrum. Gamma Rays accompany the most impressive and energetic explosions in the universe.
One way they’re produced is when a massive star, more than 50 times larger than our Sun, reaches its end and explodes, culminating in a black hole. Jets of Gamma Rays are emitted during this process, which produces an unprecedented amount of energy in a matter of seconds. They are also seen to originate when neutron stars (the collapsed core of a massive star) collide with each other. Some other theories suggest that they occur when a neutron star merges with a black hole or when two black holes collide with one another. Recent studies have observed that these emissions of gamma rays are dominated by matter, as well as the strong magnetic field created by black holes.
Types of Gamma-Ray Bursts
To understand the light intensity of a celestial phenomenon over a period of time, astronomers plot a graph called a light curve. This graph shows the specific frequencies and bands at which the light is emitted, along with various other properties, such as the intensity of the light, which provides insight about the celestial phenomenon.
In all the observations of Gamma-Ray bursts, no two explosions appear to have the same light curves. They are dissimilar in all the properties being observed, in that they have different intensities and peaks, as well as different patterns of initial brightness and subsequent fading. Some have a precursor weak burst, which then turns into a subsequent strong burst.
Therefore, one way to classify Gamma-Ray Bursts is through the duration of the explosion, as we have done below.
Short Gamma-Ray Bursts
The duration of these GRBs is less than 2 seconds and they comprise 30% of all detected GRBs. Due to their minuscule lifespan, it is difficult to detect and observe them.
Observations made after 2005 show that these events have an afterglow and are linked to elliptical galaxies and central regions of huge galaxy clusters. This rules out any connection to massive stars and supernova, suggesting that they are distinct from longer duration GRBs. Theories do link them to kilonova, the event when neutron stars collide or when a black hole eats a neutron star.
Long Gamma-Ray Bursts
These are the most well-observed GRB’s, as they occur for more than 2 seconds and are generally the most common of the observed GRB’s, comprising 70% of all detections. They most commonly occur when a massive star collapses and in the event of a supernova.
Ultra-Long Gamma-Ray Bursts
Although they represent the tail end of the Long GRB classification, lasting for more than 10,000 seconds, they are considered to be their own separate class. These long tails are seen upon the birth of a magnetar, the collapse of a blue supergiant star, or a tidal disruption event (when a star is very close to a black hole and gets pulled apart by its tidal forces).
Detailed observation about GRBs has been a recent phenomenon; as recently as 20 years ago, we didn’t have concrete evidence of what made these events occur. This changed with GRB 020813, which was observed on August 13, 2002 by the High Energy Transient Explorer, an American satellite deployed to detect Gamma-Ray Bursts. The burst went on for about 125 seconds and was linked to a massive star that went supernova. The satellite had low-resolution equipment by today’s standards, but gave us a brief insight on GRBs.
In 2008, the detection of GRB 080916C broke the record of the deadliest explosion ever recorded. It was detected by NASA’s Fermi Gamma-Ray Space Telescope on September 16, 2008. The burst had the combined energy of 5900 type la Supernova! The distance was also enormous, as the astronomers calculated it to be 12.2 billion light-years away, meaning that it happened when the universe was just 1.5 billion years old and lasted for 23 minutes.
Another record was set by GRB 130427A, which could be detected for an entire day and was one of the closest GRB ever recorded from Earth, spotted on April 27, 2013. It was detected 3.6 billion light-years away and packed the energy of 94 billion electron volts. It was one of the longer-lasting bursts, as the X-ray afterglow could be detected 6 months after the event.
The detection of GRB 190114C broke the records set to date by other Gamma-Ray Bursts. This burst was detected in January of 2019 and is the brightest event ever recorded from Earth. The event produced the energy of 1 Tera electron volts, one trillion times the energy of a photon of visible light. It is considered the brightest event since the Big Bang!
Better detection technology would enable us to detect events that might even break the record set by GRB 190114C in the future. And if it does, that will be one hell of an explosion to witness!