During its first 800 million years, Universe was a kind of opaque chamber where light could not escape. But the "Dark Ages" ended, the "smoke" dissipated and the first stars and galaxies were visible. Exactly how this process took place has been, until now, one of the biggest puzzles to which has faced in modern astrophysics.
Now, analyzing images from the Hubble Space Telescope, a team of astronomers believes it finally the answer: the "fog" was swept by a wave of ultraviolet radiation from the first generation of galaxies. Their findings are published in Nature .
During its first 300,000 years of existence, the universe was so hot (and their energy levels were so high), that subatomic particles, traveling in all directions and chaotically colliding with each other, forming a "soup" in the dense and hot that was not even may be organized into atoms.
In other words, the protons failed to "capture" electrons to form atoms of hydrogen, which is now the most abundant element, by far, the entire Universe. And if any chance it could, the nascent atomic bond was immediately broken by the force of the multiple and continuous collisions with other particles. However, 300,000 years after the Big Bang, the early Universe had already been expanded (and therefore cool) enough to loose particles begin to "relax" and form the first stable atoms of ordinary matter. Since hydrogen is the simplest of all atoms, the universe, thereafter, began to fill up the gas. And as one of the properties of hydrogen is its ability to absorb light, the young Universe was completely enveloped in darkness. BLACK
impenetrable
was how the universe came into the Dark Ages. " A black and impenetrable cloak behind which those atoms began very Slowly at first, hydrogen clouds gather in increasingly dense and turn, thanks to the action of gravity, led to the first stars and galaxies.
Thus, in absolute privacy, our universe began to be populated with the structures that are familiar to us today. The "veil" did not fall until about a billion years later, when some kind of radiation ionized the hydrogen, making everything in a clear soup of ions and electrons during a period of several hundred million years. A period that scientists know as the "Epoch of reionization."
Although researchers had always suspected the first galaxies as the main source of ionizing radiation, never been shown for that indeed was the case. So, for several decades, have proposed various theories and mechanisms that could explain the phenomenon. Intense radiation emitted by the first black holes, the energy resulting from collisions of dark matter ... The problem, however, is that none of these hypotheses has been proved. Simply
investigators had too little information on the subject as to speculate minimally viable. And it was not until recently that have begun to have tools like the Hubble, capable of sharp images of those distant times and billions of light years away. The galaxies responsible.
The final step came after the last update of the space telescope's instruments in 2009. In particular, its Wide Field Camera 3 (WFC3), able to resolve clearly the shimmering images of galaxies "only" 800 million years of the Big Bang. Just a couple of weeks that this unique instrument captures the most distant object observed so far, more than 13,000 million light years away.
Now a team of researchers led by Brant Robertson, an astrophysicist California Institute of Technology has used some of the images obtained by the WFC3 to drive directly the fault of those galaxies in the "Epoch of reionization". counting the number of these extremely distant galaxies in the Hubble pictures, Robertson and his colleagues estimated the amount of ultraviolet radiation emitted by them. To then calculate how much of that radiation was emitted into the intergalactic medium, as we have seen, in those days consisted mainly of hydrogen.
was then realized that there was more than sufficient number of photons ultraviolet to ionize almost all the hydrogen in the universe had at the time it became transparent.
BLUE EXTREMELY
Although much remains unknown about these early galaxies (such as number and type of star), which itself is clear, says Robertson, is "extremely blue" . This means that inside it was forming a large number of new stars, the kind of event capable of producing huge amounts of ionizing radiation.
The weak point of the investigation, Robertson's own admission, is the uncertainty in calculate the actual number of galaxies that had at that time, which can vary tremendously the amount of ultraviolet radiation. So you want to use the powerful Hubble camera to capture images and detect even more distant galaxies even weaker. Something that will get further increasing the already long exposure times.
Only then can fully confirm his suspicions, and unravel the mystery of how our universe grew from obscurity to be transparent
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