Could the Russians be testing their bombs on the moon?
At the time, widespread paranoia held sway and nobody knew exactly what the opposite side was capable of, so they tried to make the detectors accurate enough to be able to discover a nuclear explosion even if it were to happen on the distant moon. Even though this might seem completely incredible today, they seriously considered scenarios that Russians were even capable of testing their nuclear weapons on the dark side of the moon.
In 1963, when the two great blocs finally signed the treaty that banned nuclear weapon tests in the atmosphere, in outer space and under water, and was later joined by the majority of other countries, having control over the implementation of the ban became even more important for all sides.
Within the scientific project Vela, whose mission was to effectively detect detonations of nuclear weapons in the outer space and in the atmosphere, more than ten satellites were successively launched into orbit, equipped with detectors capable of recognizing brief pulses of extremely intense light, released by nuclear explosions. Americans sent the first pair of Vela satellites into orbit only a few days after the treaty was signed. Of course, the original model of detectors was constantly being perfected, so that by the year 1967 rockets already carried into orbit a pair of second generation Vela satellites that were equipped with substantially more accurate detectors.
Were they detecting explosions from a “galactic war”?
Soon after the first new satellites were in operation something completely unexpected happened. On the 2nd of July 1967, and for the first time, they detected bursts of gamma rays which were different from the emissions following a nuclear bomb detonation. As the entire project was being carried out in complete secrecy, a more extensive debate on the nature of this phenomenon never took place among astronomers at the time, but many great minds started to ask themselves what these bursts from outer space meant.
At the time, nobody was familiar with a natural phenomenon that could cause these flashes of high-energy rays, so scientists let their imaginations run wild. Someone suggested that this phenomenon occurred because comets made of matter and antimatter collided. Others reasoned that it was caused by small black holes exploding, or even that they had discovered a galactic war between other civilizations, unknown to man. But these were merely speculations.
During the next years, ten to twenty such bursts were discovered, and later, when the detectors were even more developed, several hundred more. It took quite some time before scientists were able to examine gamma ray bursts in detail and demonstrate clearly that they came from the depths of outer space and not from a nearby source. The first article on the existence of gamma ray bursts was not published until 1973, six long years after they had been discovered.
Where do the bursts come from?
As the question of the origin of these mysterious flashes was simply too difficult to answer, astronomers decided that they would first try to gather more information that could tell them from which ends of the universe these bursts came from. If they came from our galaxy they would all have to be spread somewhere across the area of sky covered by the stars of our galaxy which we can observe on clear nights and is well-known as the Milky Way.
In fact, only few people thought that the origins of these flashes could be outside of our galaxy in the first place, because in this case they would simply be too powerful. Energy of such magnitude could not have been the result of any known process and if there were a process that could emit such energy it would have certainly been in violation with the basic laws of physics, among others Einstein’s famous E=mc2 equation. The first credible theory was that the bursts are caused by small neutron stars from our galaxy when they are hit by an asteroid or a comet.
However, more thorough research into the location of these bursts revealed that the bursts were equally spread across the entire sky and could not have come from our galaxy, but from the more distant universe. Of course, this only meant an additional complication in finding an explanation.
The next important project scientists took on was to determine the precise distance between the sources of these bursts and the Earth. The only way to assess this distance was by using a technique called redshift. We all know that the sound of an ambulance siren is higher when the vehicle is quickly approaching us than when it is moving away from us. A similar phenomenon occurs with light in space. If a star or galaxy is moving away faster than another, it appears to be “redder” than the one that is moving away slower.
But there is another universal rule at work in outer space, called Hubble’s law: the more distant galaxies move away faster than the closer ones. The relation between the two quantities is actually very easy to establish: the farther away a galaxy is, the faster it moves away. If we can determine the degree of the redshift of a galaxy, we can evaluate how far in space it is by using Hubble’s law.
The brightest explosions in the universe
On May 9th 1997, astronomers managed for the first time to detect and observe light that followed a gamma ray burst and were able to determine in which galaxy the explosion happened. Such observations are logistically very demanding, because telescopes around the globe have to be coordinated on time, quickly enough to catch the remains of the light which follows the explosion.
When it detects a gamma ray burst, a satellite sends an SMS about the event to the astronomer on duty who immediately proceeds to coordinate the observation with one of the large robotic telescopes scattered around the globe. The most suitable telescope for observation, which may be located on the Canary Islands, Hawaii or in Australia, stops its current task and turns toward its new target in a matter of seconds.
After such successfully executed measurements it turned out that the sources of bursts are situated in very distant galaxies which at the same time means that explosions which generate gamma ray bursts are definitely the most powerful that the universe has experienced since the Big Bang. Astronomers succeeded in constructing a model enabling the explanation of even such extreme events. In fact, these bursts are very narrowly directed rays which appear to be so powerful because they do not travel to all sides of the universe, but can only be seen when they touch our galaxy.
The birth of black holes
At present, there are two possible models that can explain the formation of such high-energy light rays. According to the first model, two neutron stars collide and form a black hole. The second hypothesis proposes the explosion of a very powerful supernova explosion, called a hypernova, which also leads to the formation of a black hole.
Hypernovas are supposedly generated by very massive stars, so large that their mass causes extremely rapid combustion of fuel which enables stars to shine. In a hypernova, fuel burns out so quickly that they can not even leave the areas of the universe where stars are born. And it is this rapid consumption of fuel that causes a massive star to shrink quickly which, in turn, triggers an explosion of enormous proportions in which a sheaf of gamma rays and a black hole are created.
According to calculations, each of the two mechanisms produces a slightly different image of a burst and it is interesting that astronomers have detected bursts corresponding to the first as well as the second scenario.
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