February 6, 2014
Using Simulations To Chart The Forces Of The Early Universe
Brett Smith for redOrbit.com - Your Universe Online
Most scientific calculations need a reference point to be completed, but what if the calculations are for the beginning of the Universe – where points of reference are somewhat ephemeral?In a new study, published in the Monthly Notices of the Royal Astronomical Society, researchers from The University of Texas at Austin tried to do just that – conduct numerical simulations aimed at charting the forces of the Universe in its first hundreds of millions of years.
The study provided new conclusions on how the first galaxies formed – and how metals in the earliest stellar nurseries affected the characteristics of the stars in the first galaxies.
"The universe formed at first with just hydrogen and helium," said study author Milos Milosavljevic, an astrophysicist at the university. "But then the very first stars cooked metals and after those stars exploded, the metals were dispersed into ambient space."
Ultimately, the ejected metals dropped back into the gravitational fields of the dark matter halos, where they produced the next iteration of stars. However, the first generation of metals thrown from supernovae failed to 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," Milosavljevic explained. "You would drink some cream and coffee but not coffee with cream. There will be thin sheets of coffee and cream."
According to the astrophysicist, simple effects like these controlled the development of early galaxies. Some stars developed that were rich in metals, while some were metal-poor. There was an odd distribution of stellar chemical abundances due to the incomplete mixing, the study authors said.
Another factor that impacted the development of galaxies was how the heavier elements came from the originating blast. Rather than the neat spherical blast wave that scientists assumed before, the ejection of metals coming from a supernova was probably a messy process with blobs of debris firing in every direction.
"Modeling these blobs properly is very important for understanding where metals ultimately go," Milosavljevic said.
The earliest stars that were created are believed to have been immense and gaseous, consisting of hydrogen and helium. These stars collapsed – seeding new, smaller stars that grouped into the first galaxies. These stars would explode again, creating the conditions for stars like our own, filled with materials that enable life. How this evolution moved from one stage to the next is still a heavily-debated topic.
"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."
Many believe the early galaxies that are the subject of the new study will be observable with the James Webb Space Telescope, which is set to launch in 2018.
"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."