Dark Matter Halo

picture info	Dark Matter Halo According to modern models of physical cosmology, a dark matter halo is a basic unit of cosmological structure. It is a hypothetical region that has decoupled from cosmic expansion and contains gravitationally bound matter. A single dark matter halo may contain multiple virialized clumps of dark matter bound together by gravity, known as subhalos. Modern cosmological models, such as ΛCDM, propose that dark matter halos and subhalos may contain galaxies. The dark matter halo of a galaxy envelops the galactic disc and extends well beyond the edge of the visible galaxy. Thought to consist of dark matter, halos have not been observed directly. Their existence is inferred through observations of their effects on the motions of stars and gas in galaxies and gravitational lensing. Dark matter halos play a key role in current models of galaxy formation and evolution. Theories that attempt to explain the nature of dark matter halos with varying degrees of success include cold dark m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Cozy Bear Cozy Bear, classified by the United States federal government as advanced persistent threat APT29, is a Russian hacker group believed to be associated with one or more intelligence agencies of Russia. The Dutch General Intelligence and Security Service (AIVD) deduced from security camera footage that it is led by the Russian Foreign Intelligence Service (SVR); this view is shared by the United States. Cybersecurity firm CrowdStrike also previously suggested that it may be associated with either the Russian Federal Security Service (FSB) or SVR. The group has been given various nicknames by other cybersecurity firms, including CozyCar, CozyDuke (by F-Secure), Dark Halo, The Dukes (by Volexity), NOBELIUM, Office Monkeys, StellarParticle, UNC2452, and YTTRIUM. On 20 December 2020, it was reported that Cozy Bear was responsible for a cyber attack on U.S. sovereign national data, believed to be at the direction of the Russian government. Methods and technical capability Kaspersky L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Rotation Curve (Milky Way) The rotation curve of a disc galaxy (also called a velocity curve) is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre. It is typically rendered graphically as a plot, and the data observed from each side of a spiral galaxy are generally asymmetric, so that data from each side are averaged to create the curve. A significant discrepancy exists between the experimental curves observed, and a curve derived by applying gravity theory to the matter observed in a galaxy. Theories involving dark matter are the main postulated solutions to account for the variance. The rotational/orbital speeds of galaxies/stars do not follow the rules found in other orbital systems such as stars/planets and planets/moons that have most of their mass at the centre. Stars revolve around their galaxy's centre at equal or increasing speed over a large range of distances. In contrast, the orbital velocities of planets in planetary syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]