European Association for Astronomy Education

Source: Chandra X-ray Observatory for NASA by SAO

Credit: Illustration: NASA/CXC/M.Weiss; Spectrum: NASA/CXC/Univ. of California Irvine/T. Fang et al.

Scientists have used NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton to detect a vast reservoir of gas lying along a wall-shaped structure of galaxies about 400 million light years from Earth. In this artist’s impression, a close-up view of the so-called Sculptor Wall is depicted. Spiral and elliptical galaxies are shown in the wall along with the newly detected intergalactic gas, part of the so-called Warm Hot Intergalactic Medium (WHIM), shown in blue. This discovery is the strongest evidence yet that the “missing matter” in the nearby Universe is located in an enormous web of hot, diffuse gas.

The X-ray emission from WHIM in this wall is too faint to be detected, so instead a search was made for absorption of light from a bright background source by the WHIM, using deep observations with Chandra and XMM. This background source is a rapidly growing supermassive black hole located far beyond the wall at a distance of about two billion light years. This is shown in the illustration as a star-like source, with light traveling through the Sculptor Wall towards the Earth. The relative location of the background source, the Sculptor Wall, and the Milky Way galaxy are shown in a separate plot, where the view instead looks down on the source and the Wall from above.

An X-ray spectrum of the background source is given in the inset, where the yellow points show the Chandra data and the red line shows the best model for the spectrum after including all of the Chandra and XMM data. The dip in X-rays towards the right side of the spectrum corresponds to absorption by oxygen atoms in the WHIM contained in the Sculptor Wall. The characteristics of the absorption are consistent with the distance of the Sculptor Wall as well as the predicted temperature and density of the WHIM. This result gives scientists confidence that the WHIM will also be found in other large-scale structures.

This result supports predictions that about half of the normal matter in the local Universe is found in a web of hot, diffuse gas composed of the WHIM. Normal matter — which is different from dark matter — is composed of the particles, such as protons and electrons, that are found on the Earth, in stars, gas, and so on. A variety of measurements have provided a good estimate of the amount of this “normal matter” present when the Universe was only a few billion years old. However, an inventory of the nearby Universe has turned up only about half as much normal matter, an embarrassingly large shortfall. (read more)

Source: Space Daily

Desktop experiments could point the way to dark matter discovery, complementing grand astronomical searches and deep underground observations. According to recent theoretical results, small blocks of matter on a tabletop could reveal elusive properties of the as-yet-unidentified dark matter particles that make up a quarter of the universe, potentially making future large-scale searches easier.(read more)

Source: University of Florida

Physicists may have glimpsed a particle that is a leading candidate for mysterious dark matter but say conclusive evidence remains elusive.

A 9-year search from a unique observatory in an old iron mine 2,000 feet underground has yielded two possible detections of weakly interacting massive particles, or WIMPs. But physicists, who include two University of Florida researchers, say there is about a one in four chance that the detections were merely background noise — meaning that a worldwide hunt involving at least two dozen different observatories and hundreds of scientists will continue. (read more)

Source: ESA

X-ray emission in the COSMOS field. Credit: ESA

Observations of faint and distant galaxy groups made with the European Space Agency’s XMM-Newton observatory have been used to probe the evolution of dark matter. The results of the study are reported in the 20 January issue of The Astrophysical Journal. (read more)

Source: arXiv

Dark matter “clumping” together over time confirming  theories
of how structure formed in our evolving universe.
Credit: NASA, ESA, CalTech

Recent observational data gives an indication that the universe contains a significant fraction (22%) of dark matter whose origin is still unclear. A possible solution to this problem comes from supersymmetric (SUSY) models in the form of neutralino. Neutralino is the lightest supersymmetric partner in SUSY, with the mass of about 100GeV, and is stable. It interacts with the gravitational and weak interactions only, which indicates that it is ”dark”. Weak interactions and neutralino mass are sufficient to satisfy the relic density needed to explain the observed portion of the dark matter in the universe.

Recently a group of astronomers has obtained a detailed distribution of dark matter as a function of the redshift in a part of our universe. Their observations indicate that dark matter plays a role of a scaffolding upon which ordinary matter builds structures. However, the observations show that large pockets with only dark matter (and no ordinary matter) also exist.

De-Chang Dai and Dejan Stojkovic of HEPCOS, Department of Physics, SUNY at Buffalo, have researched the question that arises from the existence of these large pockets of dark matter that is whether compact objects like planets, stars or maybe even large may or not exist.
They concluded that, a stable neutralino star can not exist and also estimated that a stable star can not contain more than a few percents of neutralinos. This information has been published in  the Journal of High Energy Physics (JHEP)(read more)