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Diffuse Extragalactic Background Radiation
The diffuse extragalactic background radiation (DEBRA) refers to the photon field of extragalactic origin that fills our Universe. It contains photons whose energies span more than twenty orders of magnitude, from 10−7 eV to more than 100 GeV. This range covers everything from the microwaves emitted by free hydrogen atoms to ultra high-energy gamma rays, which can only be emitted by the most powerful physical processes in the modern universe such as kilonovas and merging black holes. The origin and the physical processes involved are different within every wavelength range. There is plenty of observational evidence that support the existence of the DEBRA. The figure shows a schematic picture, based on many different data sets, of the spectral intensity (also called spectral radiance) multiplied by wavelength of the DEBRA over all the electromagnetic spectrum. This representation is convenient because the area inside the curve is the energy. The nature and history of the unive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microwave
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF (millimeter wave) bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz (wavelengths between 0.3 m and 3 mm). In all cases, microwaves include the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations. The prefix ' in ''microwave'' is not meant to suggest a wavelength in the micrometer range. Rather, it indicates that microwaves are "small" (having shorter wavelengths), compared to the radio waves used prior to microwave te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultra-high-energy Gamma Ray
Ultra-high-energy gamma rays are gamma rays with photon energies higher than 100 TeV (0.1 PeV). They have a frequency higher than 2.42 × 1028 Hz and a wavelength shorter than 1.24 × 10−20 m. The existence of these rays was confirmed in 2019. In a 18 May 2021 press release, China's Large High Altitude Air Shower Observatory (LHAASO) reported the detection of a dozen ultra-high-energy gamma rays with energies exceeding 1 peta-electron-volt (quadrillion electron-volts or PeV), including one at 1.4 PeV, the highest energy photon ever observed. The authors of the report have named the sources of these PeV gamma rays PeVatrons. Importance Ultra-high-energy gamma rays are of importance because they may reveal the source of cosmic rays. Discounting the relatively weak effect of gravity, they travel in a straight line from their source to an observer. This is unlike cosmic rays which have their direction of travel scrambled by magnetic fields. Sources that produce cosmic rays will ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kilonova
A kilonova (also called a macronova) is a transient astronomical event that occurs in a compact binary system when two neutron stars or a neutron star and a black hole merge. These mergers are thought to produce gamma-ray bursts and emit bright electromagnetic radiation, called ''kilonova'', due to the radioactive decay of heavy r-process nuclei that are produced and ejected fairly isotropically during the merger process. History The existence of thermal transient events from neutron star mergers was first introduced by Li & Paczyński in 1998. The radioactive glow arising from the merger ejecta was originally called mini-supernova, as it is to the brightness of a typical supernova, the self-detonation of a massive star. The term ''kilonova'' was later introduced by Metzger et al. in 2010 to characterize the peak brightness, which they showed reaches 1000 times that of a classical nova. The first candidate kilonova to be found was detected as a short gamma-ray burst, GRB 130 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Black Hole
A binary black hole (BBH) is a system consisting of two black holes in close orbit around each other. Like black holes themselves, binary black holes are often divided into stellar binary black holes, formed either as remnants of high-mass binary star systems or by dynamic processes and mutual capture; and binary supermassive black holes, believed to be a result of galactic mergers. For many years, proving the existence of binary black holes was made difficult because of the nature of black holes themselves and the limited means of detection available. However, in the event that a pair of black holes were to merge, an immense amount of energy should be given off as gravitational waves, with distinctive waveforms that can be calculated using general relativity. Therefore, during the late 20th and early 21st century, binary black holes became of great interest scientifically as a potential source of such waves and a means by which gravitational waves could be proven to exist. Binar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffuse Extragalactic Gamma-ray Radiation
Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical potential. It is possible to diffuse "uphill" from a region of lower concentration to a region of higher concentration, like in spinodal decomposition. The concept of diffusion is widely used in many fields, including physics (particle diffusion), chemistry, biology, sociology, economics, and finance (diffusion of people, ideas, and price values). The central idea of diffusion, however, is common to all of these: a substance or collection undergoing diffusion spreads out from a point or location at which there is a higher concentration of that substance or collection. A gradient is the change in the value of a quantity, for example, concentration, pressure, or temperature with the change in another variable, usually distance. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Gamma-ray Background
Cosmic commonly refers to: * The cosmos, a concept of the universe Cosmic may also refer to: Media * ''Cosmic'' (album), an album by Bazzi * Afro/Cosmic music In music, the terms Afro/cosmic disco, “Looking over to the blogosphere, the largest hipster tremors came from the rediscovery of the Italian ‘Cosmic Disco’ sound (a mid-tempo stew of balearic disco pioneered by Beppe Loda and Daniele Balde ... * "Cosmic", a song by Kylie Minogue from the album '' X'' * CosM.i.C, a member of the Swedish rap group Looptroop Rockers * Cosmic, an album by Thomas Anders Science * An electronic medical record software developed by Cambio * Constellation Observing System for Meteorology, Ionosphere, and Climate * COSMIC cancer database * COSMIC functional size measurement Other uses * Cosmic Top Secret, a category of classified information used by NATO * Cosmic ocean, a mythological motif See also * Cosmic background (other) * Cosmos (other) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic X-ray Background
The observed X-ray background is thought to result from, at the "soft" end (below 0.3 keV), galactic X-ray emission, the "galactic" X-ray background, and, at the "hard" end (above 0.3keV), from a combination of many unresolved X-ray sources outside of the Milky Way, the "cosmic" X-ray background (CXB). The galactic X-ray background is produced largely by emission from hot gas in the Local Bubble within 100 parsecs of the Sun. Deep surveys with X-ray telescopes, such as the Chandra X-ray Observatory, have demonstrated that around 80% of the cosmic X-ray background is due to resolved extra-galactic X-ray sources, the bulk of which are unobscured ("type-1") and obscured ("type-2") active galactic nuclei (AGN). References *T Shanks, I Georgantopoulos, GC Stewart, KA Pounds,The origin of the cosmic X-ray background, ''Nature'' 353, 315 - 320 (26 September 1991); *Xavier Barcons, The X-ray Background', 1992 Cambridge University Press, 324 pages {{ISBN, 0-521-41651-5 * Audio C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extragalactic Background Light
The diffuse extragalactic background light (EBL) is all the accumulated radiation in the universe due to star formation processes, plus a contribution from active galactic nuclei (AGNs). This radiation covers almost all wavelengths of the electromagnetic spectrum, except the microwave, which is dominated by the primordial cosmic microwave background. The EBL is part of the diffuse extragalactic background radiation (DEBRA), which by definition covers the entire electromagnetic spectrum. After the cosmic microwave background, the EBL produces the second-most energetic diffuse background, thus being essential for understanding the full energy balance of the universe. The understanding of the EBL is also fundamental for extragalactic very-high-energy (VHE, 30 GeV-30 TeV) astronomy. VHE photons coming from cosmological distances are attenuated by pair production with EBL photons. This interaction is dependent on the spectral energy distribution (SED) of the EBL. Therefore, it is necessa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Infrared Background
Cosmic infrared background is infrared radiation caused by stellar dust. History Recognizing the cosmological importance of the darkness of the night sky (Olbers' paradox) and the first speculations on an extragalactic background light dates back to the first half of the 19th century. Despite its importance, the first attempts were made only in the 1950-60s to derive the value of the visual background due to galaxies, at that time based on the integrated starlight of these stellar systems. In the 1960s the absorption of starlight by dust was already taken into account, but without considering the re-emission of this absorbed energy in the infrared. At that time Jim Peebles pointed out, that in a Big Bang-created Universe there must have been a cosmic infrared background (CIB) – different from the cosmic microwave background – that can account for the formation and evolution of stars and galaxies. In order to produce today's metallicity, early galaxies must have been signif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Microwave Background
In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space. It is an important source of data on the early universe because it is the oldest electromagnetic radiation in the universe, dating to the epoch of recombination when the first atoms were formed. With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark (see: Olbers' paradox). However, a sufficiently sensitive radio telescope shows a faint background brightness, or glow, almost uniform, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The accidental discovery of the CMB in 1965 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s, and earned th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Radio Background
Cosmic commonly refers to: * The cosmos, a concept of the universe Cosmic may also refer to: Media * ''Cosmic'' (album), an album by Bazzi * Afro/Cosmic music In music, the terms Afro/cosmic disco, “Looking over to the blogosphere, the largest hipster tremors came from the rediscovery of the Italian ‘Cosmic Disco’ sound (a mid-tempo stew of balearic disco pioneered by Beppe Loda and Daniele Balde ... * "Cosmic", a song by Kylie Minogue from the album '' X'' * CosM.i.C, a member of the Swedish rap group Looptroop Rockers * Cosmic, an album by Thomas Anders Science * An electronic medical record software developed by Cambio * Constellation Observing System for Meteorology, Ionosphere, and Climate * COSMIC cancer database * COSMIC functional size measurement Other uses * Cosmic Top Secret, a category of classified information used by NATO * Cosmic ocean, a mythological motif See also * Cosmic background (other) * Cosmos (other) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
