Nasa peers back into the 'cosmic dark ages'
A massive gamma-ray burst 13 billion light years away has thrown new light on the early years of the Universe
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NASA/ Goddard Space Flight Center Conceptual Image Lab
An artist's impression of a gamma-ray burst
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The most distant object ever observed in space has provided scientists with an unprecedented insight into the "cosmic dark ages" following the birth of the Universe some 13.7 billion years ago.
A gigantic explosion on the edge of the known Universe has been confirmed as the furthermost object in the cosmos. It occurred nearly 700 million years after the Big Bang and its radiation has taken some 13 billion years to reach Earth – making it 13 billion light years away.
The explosion is one of many thousands of gamma-ray bursts that scientists have detected since they were first discovered more than 40 years ago by spy satellites designed to monitor the radiation emitted by man-made nuclear explosions. This particular gamma-ray burst, named 090423, occurred on 23 April and its afterglow lasted for about 10 seconds before it died out. This was long enough for the Swift satellite operated by Nasa to identify its location so that other telescopes on the ground could analyse the explosion in more detail.
Gamma-ray bursts are the most energetic events known to scientists. In just a couple of seconds these massively powerful explosions in space release as much energy as the Sun would release in its entire lifecycle of 10 billion years. Finding a gamma-ray burst that is 13 billion light years away means that it must have taken place within the period known as the "cosmic dark ages", a timespan of about 900 million years that separates the Big Bang from the formation of the earliest stars and galaxies.
"This observation allows us to begin exploring the last blank space on our map of the Universe. It's the first time that we've seen an object within this period of the Universe's dark ages," said Nial Tanvir, of Leicester University, who led the study published in the journal Nature.
"We're beginning to peer back to the era of the very first structures in the Universe. It's the last unexplained era because in broad-brush terms we have a reasonably good idea of what happened during the rest of the life of the Universe," he added.
Gamma-ray bursts, named after the intense amounts of gamma radiation they release, are believed to occur when massive stars some 50 or 100 times bigger than the Sun are swallowed up by a newly formed black hole, which results in the instant conversion of matter into energy.
Astronomers believe that as the black hole swallows up the dead star, intense jets of gas punch their way through the stellar material, forming interactions with other stellar gases previously shed by the dying star, causing it to heat up and release short-lived after-glows of radiation, which can be detected and measured by astronomers on Earth.
Andrew Levan, of Warwick University, another member of the international research team, said that the very ancient age of the gamma-ray burst detected in April meant that the dying star that formed it must be one of the first to be created in the early Universe.
"We're looking back into the Universe when it was very, very young and we're seeing objects that formed in the very early Universe – it was one of the first objects to form after the Big Bang," said Dr Levan.
"We thought that there were possibly stars there during this epoch but we've not until now seen them before. These early stars only lived for a few million years. They lived fast and died young," he added.
The explosion of gamma-ray burst 090423 occurred when the Universe was less than 5 per cent of its present age and a tenth of its present size.
Big Bang: Understanding the birth of the Universe
Q. Why do we think the Universe was created in a "Big Bang"?
A. Theoretical cosmologists have predicted the existence of a Big Bang for about 50 years – the theory owes its name to the late Sir Fred Hoyle, who didn't in fact believe in such a sudden beginning. However, astronomers have now made categorical observations that support the theory, including the discovery of the remnant "background radiation" left behind from the Big Bang, which now pervades the Universe.
Q. How do we know that the Big Bang occurred 13.7 billion years ago?
A. One way is to measure the speed at which the Universe is expanding and to calculate something called the Hubble constant with great accuracy. The Hubble Space Telescope did in fact do this and the calculations showed that the Universe has been expanding for about 13.7 billion years, hence the age of the Big Bang.
Q. How do gamma-ray bursts fit into the story of the Universe?
A. These are massively powerful explosions, the most energetic events known to science. They were first discovered in the 1960s by American Vela spy satellites designed to detect Soviet atomic tests. Gamma-ray bursts are thought to be the result of newly-formed black holes swallowing up massive dying stars more than 50 times the size of the Sun. So, gamma-ray bursts occur when a dying star disappears into a black hole releasing vasts quantities of energy in the form of radiation. As such they have always existed for a long as there have been stars.
Q. Will we ever see to the edge of the Universe and what lies beyond it?
A. Astronomers are seeing further and further back in time by observing objects that are further and further away from the Earth. They hope to get very close to the Big Bang but there will almost certainly be some limit on how far back they can look – perhaps these earliest objects are just too small to ever see. What happens beyond the Big Bang is largely a mystery, and a subject that cosmologists will speculate on endlessly for they are well known to be often in error, but never in doubt.
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Comments
INDY PLEASE GET RID OF THIS TRASH
Landongchen1 is a paedophile peddling crap
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Aly-Khan Satchu
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A bit like journalists then, who are always in error (as in this article) and have never heard of doubt.
As every point of space is expanding, in the 13 billion years travel hasn't the space "behind" the gamma ray burst also expanded over all this time, making is significantly further away then 13 billion years. This is why the observable universe is at least 93 billion light years across, not say 26 billion light years as you might expect.
All galaxies will recede from us, seen from the Earth. Also, they should recede at different rates depending on their location relative to us and the center of the universe, i.e. the Big Bang site. In fact, galaxies on the other side of the center will seem to recede faster because they are flying in the opposite direction, and their speed from the center is added to ours when measured from the Earth (allowing for the angles that result from the location of the galaxies and the center.)
Could it be possible that remote galaxies, such as those 13.7 million light years away are not at the edge of the universe but only on the other side of it, somewhere between the center of the universe and its perimeter, like ourselves? The light would still take the same time to reach us.
Does any of this make any sense to anyone who knows more about this subject than I? Any comments would be appreciated.
For example, you say at the end of your penultimate paragraph that the light would still take the same time to reach us. This is not true, IMHO, at Relatavistic Velocities. I studied Applied Physics, but it was 40 years ago, and we really need a recent Pure Physics Graduate to clarify these points. Anyone out there.
"If everything started with a Big bang, then presumably the explosion fragments are flying out in linear paths from the center. We (the Milky Way galaxy) are somewhere between the center of the gigantic sphere and its perimeter."
The point is that things are not flying away from a central explosion, rather every part of space is expanding. Therefore every point in the Universe can be considered the centre. Do a google search for, "Misconceptions about the Big Bang". Hubble law states that, "velocity at which various galaxies are receding from the Earth is proportional to their distance from us" Nothing more or less. Which direction the distant object is irrelevant, only the distance from us.
The age of the Universe of 13.7 billion years is taken from the Hubble Constant which defines the rate of expansion. Assuming that The Hubble Constant IS constant and has not changed with time, which may not be true since so called dark energy may be increasing the rate of expansion, then this Gamma Ray Source at 13 billion lightyears is near the outer limits of the Universe and there cannot be much behind it to expand.
The 13.7 billion is the age of the Universe and also the lightyears limit, not 26 billion, as I understand it. Remember that spacetime is expanding as the light travels through it from the Source to us. Sorry but I cannot think of a normal world way of making this clearer for you. When we are travelling at velocities near lightspeed in a vacuum, normal additive mathematics does not work. If an object is travelling from your right to left at velocity of light c, and a second object is travelling left to right at minus c, you would think that an observer on each object would see the other object approaching at 2c or minus 2c but, when you do the maths, they each see the other approaching at c or minus c. It is not logical because we have brains that evolved to deal with real world velocities whereas the Universe does not operate within those small velocities that are normal for us. I do not understand it in a comfortable real world sense but I did the maths years ago and I can assure you that it is true. The Universe, sadly, is not only weirder than we think but, probably, weirder than we CAN think!
It is nearly 40 years since I studied Relatavistic Physics so I am a bit rusty. Perhaps someone who has thought about this more recently could try an explanation.
My 26 billion light year figure for a naive calculation for the size of the observable universe as age of the Universe * 2, as the age would be the radius of the Universe. In this naive view you forget about ALL space expanding and only consider that things are moving away.
From the SA article, "Misconceptions about the Big Bang" it says, "If space were not expanding, the most distant object we could see would now be about 14 billion light-years away from us, the distance light could have traveled in the 14 billion years since the big bang. But because the universe is expanding, the space traversed by a photon expands behind it during the voyage. Consequently, the current distance to the most distant object we can see is about three times farther, or 46 billion light-years."
The topic is more complex than I remember it being but it was 40 years ago.