Simulating the Universe from the Beginning of Time
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February 06, 2014

Simulating the Universe from the Beginning of Time

 

Dark_matter_halo-wide

 

Things were different in the early eons of the universe. The cosmos experienced rapid inflation; electrons and protons floated free from each other; the universe transitioned from complete darkness to light; and enormous stars formed and exploded to start a cascade of events leading to our present-day universe.

Milos Milosavljevic, Associate Professor of Astronomy at the University of Texas, and colleagues recently reported the results of several massive numerical simulations charting the forces of the universe in its first hundreds of millions of years using some of the world's most powerful supercomputers, including the National Science Foundation-supported Stampede, Lonestar and Ranger systems at the Texas Advanced Computing Center.

The results, described in the Monthly Notices of the Royal Astronomical Society in January 2014, refine how the first galaxies formed, and in particular, how metals in the stellar nurseries influenced the characteristics of the stars in the first galaxies.

"The universe formed at first with just hydrogen and helium," Milosavljevic said. "But then the very first stars cooked metals and after those stars exploded, the metals were dispersed into ambient space."

Eventually the ejected metals fell back into the gravitational fields of the dark matter haloes, where they formed the second generation of stars. However, the first generation of metals ejected from supernovae did not mix in space uniformly.

"It's as if you have coffee and cream but you don't stir it, and you don't wait for a long enough time," he explained. "You would drink some cream and coffee but not coffee with cream. There will be thin sheets of coffee and cream."

According to Milosavljevic, subtle effects like these governed the evolution of early galaxies. Some stars formed that were rich in metals, while others were metal-poor. Generally there was a spread in stellar chemical abundances because of the incomplete mixing.

Another factor that influenced the evolution of galaxies was how the heavier elements emerged from the originating blast. Instead of the neat spherical blast wave that researchers presumed before, the ejection of metals from a supernova was most likely a messy process with blobs of shrapnel shooting in every direction.

"Modeling these blobs properly is very important for understanding where metals ultimately go," Milosavljevic said.

The simulation below shows hydrodynamic instability triggered by rapid cooling in a heavy-element-enriched cosmic dark matter halo when the universe was only 300 million years old. The instability drives turbulence which breaks the flow into fragments. Some fragments undergo gravitational collapse and set to fragment into progressively smaller units. From left to right and top to bottom, the six panels show projections of gas density, and the horizontal bar has length 1 pc = 3.26 light years. 

 

InstabilityAndTurbulence

 

In astronomical terms, early in the universe translates to very far away. Those fugitive first galaxies are unbelievably distant from us now, if they haven't been incorporated into more recently-formed galaxies already. But many believe the early galaxies lie at a distance that we will be able to observe with the James Webb Space Telescope (JWST), set to launch in 2018. This makes Milosavljevic and his team's cosmological simulations timely.

"Should the James Webb Space Telescope integrate the image in one spot for a long time or should it mosaic its survey to look at a larger area?" Milosavljevic asked. "We want to recommend strategies for the JWST."

Telescopes on the ground will perform follow-up studies of the phenomena that JWST detects. But to do so, scientists need to know how to interpret JWST's observations and develop a protocol for following up with ground-based telescopes. Cosmological simulations will help determine where the Space Telescope will look, what it will look for, and what to do once a given signal is observed.

Distant objects, born at a given moment in cosmic history, have a tell-tale signature — spectra or light curves. Like isotopes in carbon dating, these signatures help astronomers recognize and date phenomenon in deep space. In the absence of any observations, simulations are the best way of predicting these light signatures.

"We are anticipating observations until they become available in the future," Milosavljevic said.

If done correctly, such simulations can mimic the dynamics of the universe over billions of years, and emerge with results that look something like what we see — or hope to see with new farther-reaching telescopes.

"This is a really exciting time for the field of cosmology," astronomer and Nobel Laureate Saul Perlmutter said in his keynote address at the Supercomputing '13 conference in November. "We are now ready to collect, simulate and analyze the next level of precision data... there's more to high performance computing science than we have yet accomplished."

In addition to the practical goals of guiding the James Webb Space Telescope, the effort to understand these very early stars in the first galaxies has another function: to help tell the story of how our solar system came to be.

The current state of the universe is determined by the violent evolutions of the generations of stars that came before. Each generation of stars (or "population," in astronomy terms) has its own characteristics, based on the environment it was created in.

The Population III stars, the earliest that formed, are thought to have been massive and gaseous, consisting initially of hydrogen and helium. These stars ultimately collapsed and seeded new, smaller, stars that clustered into the first galaxies. These in turn exploded again, creating the conditions of Population I stars like our own, chock full of materials that enable life. How stars and galaxies evolved from one stage to another is still a much-debated question.

"All of this was happening when the universe was very young, only a few hundred million years old," Milosavljevic said. "And to make things more difficult, stars — like people — change. Every hundred million years, every 10 million years — it's like a kid growing up, all the time something new is happening."

Simulating the universe from birth to its current age, Milosavljevic and his team's investigations help disentangle how galaxies changed over time, and provide a better sense of what came before us and how we came to be.

The Daily Galaxy via University of Texas

Image credit top of page: http://www.bhmpics.com/walls/dark_matter_halo-wide.jpg

Comments

Along with this cosmic evolution, which is the probability that within a galaxy like the milky way, from the dust of its exploded stars, the living being who uses a computer was formed - computer included? A favourable case among infinite unfavourable possibilities? Fifty-fifty? To be or not to be, is that the question? Or is it a zero followed by a radix point and an infinite amount of zeros behind, but finishing with a one emerging from error or compassion when rounding up? Are calculations simplified or made more complex when the subjective self of each one is the entity that is studied? Anyway , what is the relationship between life and immense numbers? Is life a folding process of infinity? Is it just something infinite that would have enough to allow a self, something of infinite claims? But, is infinity credible within something with a beginning, out of a Big Bang? And is it credible within something with an ending, with the inevitable death around the corner? Along these lines, there is a peculiar book, a preview in http://goo.gl/rfVqw6 Just another mind leisure suggestion, far away from dogmas or axioms.

Completing the reading of the first paragraph of this article, I made a small break to classify the questions that were created with the reading of the paragraph. Those questions were:
-Electrons and protons how created? For electrons I have not found an answer. For protons, the answer was that they were created by triads of quarks, but the question that remained was how the quarks were created?
-How, protons and neutrons, remaining in such a small space, not mutually destroyed? The answer I found was that in the beginning of the creation did not work the laws of nature as we know them: I not considered it like a satisfactory answer.
-Which were the quantities of the above particles created? And what criteria determined these quantities? None answer.
-Today I read in various books that at the creation of the Universe took place and many other particles,-Higgs etc-. These particles how were created?
I will not bore you with the other questions, I have noted. But however, when red the rest of the article note and many other questions such as:
-How were the fundamental forces of the universe and especially gravity created?
-Does at the centers of galaxies we observe nothing of material, because there is nothing etc.
Completing reading the article, which is actually a pretty interesting article, I thought: Does science alongside the investigation, in the details of the creation, -were has now gathered all its attention-, must remember and deal with the essential questions that remain unanswered?

Time never had a beginning, it just lacked curious minds to invent it.

Knize....brilliant!

Right on Knize10. People just have a difficult time grasping such a concept because our lives here have a beginning and an end.

Time is a measure of change. There does not have to be a 'mind' to witness that change. It will occur with or without 'us'.

@Casey Kazan

If we assume Big-Bang as only one of the cosmic events in the history of the Universe, then for us "Time" definitely has a beginning.

Overall we will never be able to figure it out, unless people wish to get into Godly stuff then they can surely accept what the religion or the spirituality says.

In my opinion questions related to time, energy etc can never be figured out.

Hello, Concerning protocols for prioritizing where and how to direct the James Webb Space Telescope I would like to make a humble consideration. We know that the shape and observable view of the universe is not as it appears, however we must direct the observations as they appear. I am feeling that once images of the very first Galaxy material arriving into this Stelliferous Epoch out of the Opaque Epoch begin to be found, a full and complete spherical 3 dimensional map set of the observable universe should be able to be properly created. These initial maps would from initial necessity be with the observing instrument centered, so that future work can be completed on the best map. Such future work should be done in such a way as to create a map of the universe as it actually is, which will be very different from how it is observed. This, I am humbly suggesting, is why I feel the James Webb Space Telescope should be prioritized to seek galaxy material arising out of the opaque epoch. Finding such will also have great importance for other things besides discovery of the actual mapping of the universe being possible once the center area is discovered. This will discover the final stages of transition to this transparent epoch from the opaque epoch, and with work, discovery of processes of particle physics that are complexively involved, including whether or not there actually is Dark Matter. There may not be Dark Matter, in which instance Gravity's properties will need further researching.


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