Fr.: pixel chaud
Of a → CCD detector, a pixel that has higher charge loss. Hot pixels are a type of noise affecting almost every CCD camera. They are caused by small contamination or production faults in the CCD sensor area.
lekke-ye dâq (#)
Fr.: point chaud
A compact, highly luminous region in a cataclysmic binary located in the accretion disk where the stream of material hits it.
setâre-ye dâq (#)
Fr.: étoile chaude
A member of a class of stars having high → effective temperatures (above some 15,000 K); mainly → massive stars, but also including → exciting stars of → planetary nebulae, → white dwarfs, and → symbiotic stars.
internal photoelectric effect
oskar-e šid-barqi-ye daruni
Fr.: effet photoélectrique interne
The → photoelectric effect whereby photons absorbed by a solid (→ semiconductor) raise electrons from a lower to a higher → energy level (from → valence band to → conduction band). See also → external photoelectric effect.
Of or relating to → isophotes.
Fr.: rayon isophotal
The size attributed to a galaxy corresponding to a particular level of → surface brightness. The reason is that galaxies do not have sharp edges.
A line joining points with the same surface brightness on a plot or in image of a celestial object such as a nebula or galaxy.
Isophote, from → iso- + a combining form of Gk. phos (gen. photos) "light."
Izošid, from izo-, → iso-, + šid "light, sunlight," from Mid.Pers. šêt "shining, radiant, bright;" Av. xšaēta- "shining, brilliant, splendid, excellent."
Fr.: photon de Lyman-Werner
An → ultraviolet photon with an energy between 11.2 and 13.6 eV, corresponding to the energy range in which the Lyman and Werner absorption bands of → molecular hydrogen (H2) are found (→ Lyman band, → Werner band). The first generation of stars produces a background of Lyman-Werner radiation which can → photodissociate molecular hydrogen, the key → cooling agent in metal free gas below 104 K. In doing so, the Lyman-Werner radiation field delays the collapse of gaseous clouds, and thus star formation. After more massive → dark matter clouds are assembled, atomic line cooling becomes effective and H2 can begin to shield itself from Lyman-Werner radiation.
šidsanji-ye bârik bând
Fr.: photométrie à bande étroite
Photometry using narrow-band filters to isolate a particular spectroscopic line or molecular band.
The supersymmetric partner of the → photon.
From phot, from → photon + -ino supersymmetric particle suffix.
šid- (#), nur- (#)
From Gk. combining form of phos (genitive photos).
Šid- "light, sunlight," from Mid.Pers. šêt "shining, radiant, bright;"
Av. xšaēta- "shining, brilliant, splendid, excellent."
A situation in which all of the energy of a photon is transferred to an atom, molecule, or nucleus.
Electrode capable of releasing electrons when illuminated.
The study of the chemical and physical changes occurring when a molecule or atom absorbs photons of light.
Th desorption of surface substances by ultraviolet radiation.
The process by which atomic nuclei are broken apart into their constituent protons and neutrons by the impact of high energy gamma photons. Photodisintegration takes place during the core collapse phase of a → Type II supernova explosion.
photodissociation region (PDR)
nâhiye-ye šid-vâhazeš, ~ nur-vâhazeš
Fr.: région de photodissociation
A neutral region at the boundary of a → molecular cloud created by the penetration of → far ultraviolet (FUV) radiation from associated stars. The FUV radiation (6 eV ≤ hν ≤ 13.6 eV) dissociates the molecules and heats the gas and dust. A warm, atomic → H I region is thus created and the chemistry and thermal balance of the region are determined by the penetrating FUV photons. The progressive absorption of FUV photons leads to the occurrence of transitions between atomic and molecular phases, such as H I/H2 and C II/C I/CO transitions. By extension, any neutral region where the physics is controlled by FUV photons can be called a PDR, as it is the case for → diffuse interstellar clouds or the edge of → circumstellar disks. The PDR concept was first studied by A. G. G. M. Tielens and D. Hollenbach (1985, ApJ 291, 722).
Pertaining to electronic or other electrical effects that are due to the action of electromagnetic radiation, especially visible light.