Knowra Warm–hot intergalactic medium Warm–hot intergalactic medium The warm–hot intergalactic medium is diffuse gas between galaxies at roughly 10⁵–10⁷ kelvin. It is thought to contain a substantial share of the universe’s ordinary matter.
Cosmic web : The large-scale network of matter in the universe, consisting of filaments, sheets, and nodes separated by voids. The gas occupies the web’s filaments and helps trace its otherwise faint structure.
Baryon : A particle made of three quarks, including protons and neutrons, that contributes to ordinary matter. The medium is part of the universe’s baryonic matter, not its dark matter.
Missing baryon problem : The discrepancy between the number of baryons inferred in the early universe and those readily observed in the present universe. The warm–hot medium is a leading proposed reservoir for the hard-to-detect baryons.
Fast radio burst : A brief, bright pulse of radio emission originating beyond the Milky Way. Its dispersion can help inventory ionized baryons between galaxies.
Gravitational shock heating : The conversion of infalling gas’s gravitational energy into heat at shocks during structure formation. Shocks heat intergalactic gas as matter falls into developing cosmic structures.
Intergalactic medium : The gas and plasma occupying the space between galaxies. The warm–hot phase is one temperature component of this broader reservoir.
X-ray astronomy : The study of celestial objects through their emitted or absorbed X-rays. X-ray observations can detect the hottest and densest portions of the medium.
Circumgalactic medium : Gas and matter surrounding a galaxy beyond its visible stellar disk but within its gravitational influence. Its boundary with intergalactic gas complicates estimates of how much matter lies in each reservoir.
Thermal bremsstrahlung : Radiation produced when charged particles, especially electrons, are deflected by other charged particles. Hot, dense regions of this gas can emit X-rays through electron-ion encounters.
Ionized gas : Gas whose atoms or molecules have lost or gained electrons, leaving charged particles. At these temperatures, much of the medium is ionized and interacts with radiation and magnetic fields.
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