Blast from the Past Gives Clues About Early Universe

Oct 28, 2009
Antennas of the Very Large Array. Image: NRAO/AUI/NSF

(PhysOrg.com) -- Astronomers using the National Science Foundation's Very Large Array (VLA) radio telescope have gained tantalizing insights into the nature of the most distant object ever observed in the Universe -- a gigantic stellar explosion known as a Gamma Ray Burst (GRB).

The explosion was detected on April 23 by NASA's , and scientists soon realized that it was more than 13 billion light-years from Earth. It represents an event that occurred 630 million years after the Big Bang, when the Universe was only four percent of its current age of 13.7 billion years.

"This explosion provides an unprecedented look at an era when the Universe was very young and also was undergoing drastic changes. The primal cosmic darkness was being pierced by the light of the first stars and the first galaxies were beginning to form. The star that exploded in this event was a member of one of these earliest generations of stars," said Dale Frail of the National Radio Astronomy Observatory.

Astronomers turned telescopes from around the world to study the blast, dubbed GRB 090423. The VLA first looked for the object the day after the discovery, detected the first from the blast a week later, then recorded changes in the object until it faded from view more than two months later.

"It's important to study these explosions with many kinds of telescopes. Our research team combined data from the VLA with data from X-ray and infrared telescopes to piece together some of the physical conditions of the blast," said Derek Fox of Pennsylvania State University. "The result is a unique look into the very that we couldn't have gotten any other way," he added.

The scientists concluded that the explosion was more energetic than most GRBs, was a nearly-spherical blast, and that it expanded into a tenuous and relatively uniform gaseous medium surrounding the star.

Astronomers suspect that the very first stars in the Universe were very different -- brighter, hotter, and more massive -- from those that formed later. They hope to find evidence for these giants by observing objects as distant as GRB 090423 or more distant.

"The best way to distinguish these distant, early-generation stars is by studying their explosive deaths, as supernovae or Gamma Ray Bursts," said Poonam Chandra, of the Royal Military College of Canada, and leader of the research team. While the data on GRB 090423 don't indicate that it resulted from the death of such a monster star, new astronomical tools are coming that may reveal them.

"The Atacama Large Millimeter/submillimeter Array (ALMA), will allow us to pick out these very-distant GRBs more easily so we can target them for intense followup observations. The Expanded , with much greater sensitivity than the current VLA, will let us follow these blasts much longer and learn much more about their energies and environments. We'll be able to look back even further in time," Frail said. Both ALMA and the EVLA are scheduled for completion in 2012.

The scientists described their research in a paper submitted to the Astrophysical Journal Letters.

: Among the most powerful events in the , a gamma-ray burst is believed to be the extremely powerful energy discharge of a black hole forming from the death of a giant star. Though the gamma-ray emission lasts only a few minutes to hours, the radio wave afterglow from the burst can last more than a year, making long-term observations of these enigmatic objects possible.

Source: National Radio Astronomy Observatory (news : web)

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RayCherry
not rated yet Oct 28, 2009
Is it just me? Light and sound from an event in the early universe moves away from the source at the speed of light and yet remains within the same universe to be 'witnessed' by a part of the same universe that exists much later? If it is an echo/reflection via cosmic lense(s), then how can we understand the geometry enough to say the wave was spherical? If it is not a cosmic echo, do we have the age and/or the early expansion rate right? Or, did this event get trapped inside an area of space that slowed down the Gamma Ray burst enough to arrive at our area so much time after the event? If the last sentence is true, are we looking directly where our galaxy originated?
GSwift7
5 / 5 (1) Oct 28, 2009
Sorry RayCherry, but you'll have to look at it a little differently. Think of the entire universe as the skin of an expanding balloon. Then think of the part we can see as just a small patch on that skin. If you look sideways across the inside of the skin, then you can see things that are far enough away that they happened very very long ago. Your assumption that we are trying to look straight toward the starting point of the big bang is a little wrong in concept, if you see what I mean. Hope that helps a little. I tried to keep it as over-simplified as possible.
RayCherry
not rated yet Oct 29, 2009
Thanks Mr. Swift for your use of the standard analogy referring to all objects in the universe appearing to grow more distant from each other, which gave rise to the famous Feignman models of the expanding universe.

The real question is, could our area of the universe move so much faster than the speed of light during any time in the development of the same universe, that would mean that the source of this gamma ray burst was once an 'immediate neighbour' of ours and yet today we can witness 'once more' an event that must have taken place when we were 'very nearby'? Is it feasible that our area of the universe could be propelled by the force of the initial expansion, that it could outrun light for thirteen billion years? Or ... did the Big Bang ocurr a 'little' earlier than we currently calculate?

My physics tutor once answered one of my questions with "God knows!" :-)

Perhaps we would have to have been there to answer these questions ...
GSwift7
5 / 5 (1) Oct 30, 2009
(Toung planted firmly in cheek)

Two problems:

First, our area of the universe isn't proposed to have moved faster than the speed of light. You're falling into the trap of trying to relate this to Newtonian physics. The objects in the universe aren't what expanded, it was spacetime itself that expanded.

Second: The extremely rapid expansion happened before the GRB, so it was already extremely far away from us when it happened. The rapid expansion is thought to have happened in the very first few instants of existence of the universe.

I kind of have my doubts about that expansion though. It seems like we are just placing a bandaid over the part of the problem that we don't know how to solve. I'm guessing that a new theory about the very beginning of the universe will eventually replace the current view, once we know more. There's some big thing we are missing right now. Maybe the problem is that we, as humans, just aren't capable of perceiving it. That would suck, wouldn't it
amcke001
not rated yet Nov 08, 2009
I agree with GSwift7. It makes sense if you consider that the universe had already undergone rapid expansion. Im also on the same side questioning how the great expansion was modeled, perhaps due to cooling temperatures past a threshold. I'm fairly confident that whomever is working on these problems is far more qualified than I