Introduction
There are thousands of galaxies, each with billions of stars. The total number of stars in our universe may be greater than 7×(10^22). Well, Can we gather the energy radiated by all these stars for a period of a hundred million years? Then we could gather the huge power, and use it to fire the biggest super-weapon in the universe. Well, It turns out. You don’t need to imagine it. This actually happens. There exists such phenomena, and they are called gamma-ray bursts.
Before discussing the phenomenon of gamma ray bursts, we must be familiar with the gamma rays. Gamma rays or gamma radiations are electromagnetic radiations. The list of electromagnetic radiation includes Gamma rays, X-rays, UV rays, Visible rays, IR rays, Radiowave, and Microwave. The electromagnetic radiations are not new to us. The most common example is the visible light. The electromagnetic radiations are the waves which carry energy just like visible light. Visible spectrum occupies a small region of the electromagnetic spectrum.
The visible spectrum helps our eyes see the objects, the Earth, the stars, and the universe. If we arrange the radiation with increasing wavelength, their energy will decrease with increasing wavelength. Above the visible range, there are radio waves, microwaves, and infrared waves at lower energies. There are ultraviolet (UV) radiations, X-rays, and gamma rays with higher energies.
Gamma rays possess incredible power. The electromagnetic radiations are quantized. Each quantum or bundle of radiation may be referred to as a ‘photon‘. A single gamma ray photon is more energetic than a million photons of visible radiation. Gamma rays possess the highest energy in the electromagnetic spectrum. Their energies are more than 100 keV, whereas a photon of visible light possesses energies ranging from 2 to 2.75 electron volts (eV), although both travel at the same speed in a vacuum, i.e., 299792458 m/s.
The gamma rays are energetic enough to break apart atomic bonds. Therefore, the high energy of gamma rays is useful to make them a form of ionizing radiation. This characteristic of gamma rays makes them dangerous to you, me, and all human beings. Ionizing radiation disrupts the biochemical machinery that keeps us alive. It is the ozone layer that blocks gamma rays coming from space towards Earth. The ozone layer of the atmosphere filters these lethal radiations out before they can reach the Earth’s surface and harm us.
Discovery of Gamma Ray Burst
The atmosphere surrounding our planet has different layers, namely, Troposphere, Stratosphere, Mesosphere, Ionosphere, and finally Exosphere. The ozone layer of the atmosphere is related to the stratosphere layer which starts about 10–16 km above the ground and extends up to about 50 km. The ozone layer is found in the lower part of the stratosphere.
The ozone layer blocks gamma rays coming from space. That is why the detection of gamma ray bursts from the surface of the Earth is not easy. During the Cold War, the USA sent up spy satellites, which could detect gamma rays from Soviet nuclear tests in space. However, the satellites didn’t see any blast of bombs, but they did observe faint bursts coming from space, lasting only a few seconds. To date, this is the only major scientific discovery made by spy satellites that we know about anyway.
Astronomers use telescopes to see different kinds of light to make their discoveries. Although these spy satellites gave them a new pair of eyes, the gamma ray bursts were a mystery for 30 years. Eventually, the source of gamma ray burst (GRB) was discovered in a galaxy that is six billion light years away. If a GRB can be seen from such a distance, then it must be incredibly energetic. GRBs accompany some of the most violent deaths in the universe, and the birth of black holes.
Types of Gamma Ray Burst
There are two types of gamma ray bursts(GRB). They are short gamma-ray bursts and long gamma-ray bursts. Each type of GRB has its own source. Long GRBs last about a minute, whereas short GRBs last for less than two seconds. That is why they are named accordingly. Scientists think that long GRBs are produced by supernovas when the core of a massive star collapses to become a black hole.
On the other hand, short GRBs are brief flashes of high-energy radiations. They are produced when two neutron stars merge or a neutron star merges with a black hole. Before the merging of neutron stars, their orbits shrink continuously over millions of years due to the emission of gravitational waves. Finally, they crash and splash into each other and a black hole is formed.
Gamma-ray bursts happen when black holes form from their parent stars. Black holes are surrounded by magnetized discs of gas. The rotation winds up the magnetic field, which funnels hot jets of particles traveling with high speed comparable to that of light. The gas in this funnel creates high-energy gamma rays. The GRB so created can be seen from much further unlike the other cosmic explosions, which spread out and fade.
Dangers of Gamma Ray Burst
Gamma ray bursts may be one possible cause of the Ordovician extinction 450 million years ago. The burst eradicated almost 85% of all marine species, although it’s pretty difficult to prove. GRBs take place in our universe and they are hitting us all the time. We detect at least one per day, but most are harmless. All of those detected bursts are originated outside the Milky Way. That is why they are unable to hurt us. If GRB takes place within a few light years of our planet, at least half of its surface would have burnt.
Ozone takes years to replenish itself by natural processes which is more than enough time for the sun to burn the Earth sterile. This may have already happened on different planets of the universe. That is why we fail to find life anywhere else in the universe. Only 10% of all galaxies might be hospitable to life similar to Earth due to GRBs. GRBs are probably not going to kill us. If there could already be a GRB on its way to kill us all, we would not do anything. We won’t know it until it hits us and ends up our lives.
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