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Category: cosmology – Page 413

A new era in the quest for dark matter

Since the 1970s, astronomers and physicists have been gathering evidence for the presence in the universe of dark matter: a mysterious substance that manifests itself through its gravitational pull. However, despite much effort, none of the new particles proposed to explain dark matter have been discovered. In a review that was published in Nature this week, physicists Gianfranco Bertone (UvA) and Tim Tait (UvA and UC Irvine) argue that the time has come to broaden and diversify the experimental effort, and to incorporate astronomical surveys and gravitational wave observations in the quest for the nature of dark matter.

Over the past three decades, the search for dark matter has focused mostly on a class of particle candidates known as weakly interacting massive particles (or WIMPs). WIMPs appeared for a long time as a perfect dark matter candidate as they would be produced in the right amount in the early universe to explain dark matter, while at the same time they might alleviate some of the most fundamental problems in the physics of elementary particles, such as the large discrepancy between the energy scale of weak interactions and that of .

We’ve Just Found The Source of Some of The Most Powerful Light Beams Ever Detected

Matter ejected from a spinning disc of doom surrounding a black hole a mere 15,000 light years away has produced some of the most energetic rays of light ever witnessed from an object of its kind.

The insanely powerful photons of gamma radiation were produced by a never-before-seen phenomenon surrounding a miniature quasar. The discovery could help us better understand what goes on deep in the chaotic heart of the Milky Way.

SS 433 is a smaller version of the kinds of maelstrom of death you’d find lurking at the core of most galaxies. It’s also in our neighbourhood, more or less, making it relatively easy to study.

New observations to understand the phase transition in quantum chromodynamics

The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved nearly freely in a quark-gluon plasma. Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons.

In the current issue of Nature, an international team of scientists has presented an analysis of a series of experiments at major particle accelerators that sheds light on the nature of this transition. The scientists determined with precision the transition temperature and obtained new insights into the mechanism of cooling and freeze-out of the -gluon plasma into the current constituents of matter such as protons, neutrons and . The team of researchers consists of scientists from the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, and from the universities of Heidelberg and Münster (Germany), and Wroclaw (Poland).

A central result: The record-breaking high-energy experiments with the ALICE detector at the Large Hadron Collider (LHC) at the research center CERN produced matter in which particles and antiparticles coexisted in equal amounts, similar to the conditions in the . The team has confirmed via analysis of the experimental data theoretical predictions that the phase transition between and hadronic matter takes place at the temperature of 156 MeV, 120,000 times higher than that in the interior of the sun.