February 1, 2013
Lack Of Dwarf Galaxies Around Milky Way Perplexes Physicists
Brett Smith for redOrbit.com - Your Universe Online
Studying the physics of the universe can be a controversial and often contradictory proposition, with theories and calculations often not matching with observations.
However, new research from Leibniz Institute for Astrophysics Potsdam in Germany, has shed some light on one situation involving differences between theory and observation.
Scientists at the institute have found that a phenomenon known as “cosmic web stripping” is responsible for the lack of dwarf galaxies near the Milky Way that should be there according to the theory of cold dark matter and dark energy.
Based on the last two decades of observational data, astrophysicists have determined that the universe is composed of 75 percent dark energy, 20 percent dark matter and 5 percent ordinary matter.
Contrary to what you might see on paranormal investigation reality shows, dark energy is the term used to describe a theoretical form of energy that permeates the entire universe and causes the expansion of the universe to accelerate.
Dark matter cannot be seen directly, but its effects can be observed through its manipulation of visible matter and radiation. Its unseen mass can warp light and radiation from nearby stars and this effect can be observed using modern technology. Astrophysicists came to acknowledge the existence of dark matter when they determined that there is more mass in the universe than what is visible.
Throughout the universe, galaxies and matter bunch together into an intricate network of filaments and voids that scientists refer to as the cosmic web. Supercomputer simulations designed to model the cosmic web have shown that there should be a large number of dwarf galaxies, about one thousandth the mass of the Milky Way, within relatively close proximity to Earth--about 10,000,000 light years. However, only a few of these galaxies have been seen orbiting the Milky Way.
To investigate why there appeared to be a lack of nearby dwarfs, an international team of researchers within the Constrained Local UniversE Simulations project (CLUES) decided to take a closer look at the positions and behaviors of nearby galaxies. Based on these inspections, the team was able to construct a more detailed model of the Milky Way´s neighborhood.
“The main goal of this project is to simulate the evolution of the Local Group - the Andromeda and Milky Way galaxies and their low-mass neighbors - within their observed large scale environment,” Stefan GottlÃ¶ber of the Leibniz Institute, said in a statement.
Using the new models, the researchers found that some of the Milky Way´s farthest dwarf neighbors move with such high speeds that most of their interstellar gas is stripped off. The astronomers dubbed this newly observed phenomenon, “Cosmic Web Stripping”, because the cosmic web is ultimately responsible for the loss of the dwarfs´ gas supply.
“These dwarfs move so fast that even the weakest membranes of the Cosmic Web can rip off their gas”, explained study co-author Alejandro BenÃtez LLambay, from the Universidad Nacional de CÃ³rdoba in Argentina. “Without a large gas reservoir out of which to form stars, these dwarf galaxies should be so small and dim that they would be hardly be visible today. The missing dwarfs may simply be too faint to see [sic].”