Out there in the depths of space lurks something so deadly it destroys everything in its path. Explosions of inconceivable power are tearing through the Universe hundreds of times a day. For years science has been on a quest to find out what was causing these explosions and now, at last, they may have found the answer. What they have discovered is that these forces of destruction may hold the key to one of the great secrets of creation: how you and I came to be. When we look up at the night sky we see thousands of stars shining brightly. In fact, there are billions upon billions of stars stretching across the Universe, but it wasn't always this way. Once there was a time when there were no stars. There was nothing to light up the sky. This time of darkness was just after the Big Bang, 14 billion years ago.
The entire Universe started off as a hot fireball and it cooled down and after about half a million years our Universe entered a literal dark age. The Universe then stayed dark until the first stars formed and lit it up again.
Lost inside this cosmic dark age is one of the great mysteries of science: the very first stars, the creators of everything. Stars are the factories of the Universe. Inside their burning cores, all the elements that make up everything we see and touch today are created, but without those very first stars to begin this process of creation there would be no galaxies, no Earth, no us. A great puzzle at the heart of this creation story is, if the stars create everything then how were the very first stars themselves created all those billions of years ago? It is a mystery that has baffled scientists for generations.
But no matter how hard we look no one has been able to see back to the cosmic Dark Age, until now. Something has been discovered that may light up the darkness of the early Universe and solve the mystery of how the very first stars were made, something that sends science on a quest that would span the entire Universe.
Who would have thought that this journey would take us to the edges of the Universe, the biggest explosions in nature, black hole birth, star death? Just the most exotic phenomena that I've ever seen and I've been studying explosions all my life.
The journey began over half a century ago with a bizarre chain of events at the height of the Cold War.
It was the 1950s and the world was gripped by fear. The Americans were convinced the Russians were trying to develop nuclear weapons behind their back and because they thought the Communists are devious they decided that the most likely testing site for these new weapons was not in the oceans, not in the deserts, in fact not even on Earth itself. The Americans believed the Soviets were testing nuclear bombs on the dark side of the Moon.
I mean come on, give me a break type of thing nowadays. The ridiculousness of it, the, the, but the Soviets would buy into the same paranoia because their paranoia was, you know, might say more deeply inbred.
Stirling Colgate was an expert in nuclear bomb testing. He was put in charge of designing a series of satellites sensitive enough to pick up even the faintest trace of a nuclear explosion from as far away as the Moon.
So the satellites were made to detect nuclear violators, cheaters, which meant they had to be a great deal more sensitive than any sensible bomb physicist would have ever said they needed to be.
Colgate's satellite was designed to pick up the one tell-tale sign of a nuclear explosion that not even the Russians could hide. Gamma rays, the deadliest form of energy in the Universe.
A typical gamma ray can go through about that much lead [6-8cm] and that means a good, good number of them will deposit in your body and they can do biological damage.
With every nuclear explosion there is a deadly blast of gamma rays. If the Communists were testing bombs on the Moon then Stirling Colgate's satellite would spot them. Colgate's satellite was launched amidst great secrecy, but what it would discover would turn out to be far more deadly than a Russian nuclear bomb. On 2 July 1967 it seemed their worst nightmare had come true. Colgate's satellite picked up a huge burst of gamma rays.
A nuclear bomb signal that you'd expect to see from a test in space of a nuclear weapon would be first a pulse, smaller pulse, then followed by some time a much bigger pulse and these two pulses are the primary and the secondary.
But the tell-tale signal was not from any nuclear bomb. It was from something far, far bigger, something of incomprehensible size.
And the signals just kept on coming. Something out there was causing huge explosions blasting out deadly gamma rays.
No one really knew quite what to make of it and there were, there were preposterous ideas bandied around for a while that even these were interstellar star wars going on and we were seeing the, the phaser blasts that missed their target, or that comets were annihilating with anti-comets or little black holes were evaporating. People didn't quite know what to make of it.
The journey that would one day lead science back into the cosmic Dark Age had begun. Astronomers were baffled. They had no idea what was causing these bursts. The most likely cause, they thought, was some kind of exploding star, but to be sure they turned to no less an authority than Einstein and to one of the most fundamental of all the laws of physics: E=mc². This famous equation underpins many of our assumptions about how the Universe works. It puts a limit on the size of any explosion. Nothing can explode with more energy than is contained in its mass, so if some kind of star really was the source of these gamma ray bursts then E=mc² would tell you how big the explosions could be.
The mystery began in 1967. A US military satellite was launched to detect Soviet nuclear tests which the Pentagon believed were secretly taking place on the dark side of the Moon. Instead, the satellite picked up evidence of explosions far bigger than any bomb. Something was emitting bursts of gamma rays - the deadliest form of energy known - on a massive scale. What was worse, these blasts just kept on coming.
Breaking the law
For decades scientists were baffled. Especially disturbing was evidence that these explosions might be coming from the furthest reaches of the Universe, billions of light years away. If this was so, then for us to see them on Earth they had to be on a scale that was beyond our comprehension. According to some, these explosions were so huge that they might even violate the most sacred law in all science: Einstein's famous equation relating mass and energy, E=mc². That law underpins nothing less than our understanding of how our Universe works.
Live fast, die young
It was not until 1997, when a satellite pinpointed the exact location of these bursts, that scientists began to solve the puzzle. It seems these huge explosions are caused by the death throes of stars twenty times the size of our Sun, which burn themselves out and explode, creating hypernovae. What then unfolded was a chain of events, which would ultimately point towards some of the most exotic wonders in the Universe: stellar nurseries (where new stars are born) and black holes.
Observations show that - instead of fading away, as an explosion might be expected to - radiation continues to emerge from the area of a hypernova. This ongoing emission is characteristic of the process of star birth. Astronomers conclude that the hypernova grows rapidly along with other normal stars in a nursery, but burns out when its contemporaries are still in their infancy.
Pointing to the past
Find a hypernova, therefore, and you have also tracked down a part of space where stellar synthesis is underway. Which is why some scientists now believe that the huge explosions of hypernovae may be the key to unlocking one of the great unsolved mysteries in the Universe: how the first stars were made at the very dawn of time.
All hail to Colgate`s Sattelite.
Source:
http://www.bbc.co.uk/science/horizon/2001/deathstartrans.shtml
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