blue halo star
setâregân-e âbi-ye hâlé
Fr.: étoiles bleues du halo
A star belonging to a variety of stars located above the → horizontal branch and blueward of the → red giant branch in the → Hertzsprung-Russell diagram of the → halo population.
Setâregân plural of setâré, → star, âbi, → blue, hâlé, → halo.
Fr.: galaxie cœur-halo
A radio galaxy characterized by an emission "halo" surrounding a more intense "core". About 20% of the known extended radio sources are of the core-halo type.
dark matter halo
hâle-ye mâde-ye târik (#)
Fr.: halo de matière sombre
A vast region surrounding a galaxy where dynamical tracers reveal a large amount of → hidden mass. The halo has considerable mass but relatively low luminosity, suggesting the presence of a lot of → dark matter.
Fr.: halo galactique
A roughly spherical aggregation of → globular clusters, as well as the oldest stars and unseen mass that surrounds the Galaxy.
1) Meteo.: Rings or arcs that seem to encircle the sun or moon and are the result
of the refraction of light through the ice crystals that make up
Halo, from L. (acc.) halo, from Gk. halos "ring of light around the sun or moon."
Hâlé, loanword from Ar.
halo occupation distribution (HOD)
vâbâžeš-e hageš-e hâlé
Fr.: distribution d'occupation de halo
The → probability distribution of the → number of galaxies that a host → dark matter halo of a given mass contains. HOD is a powerful theoretical frame to populate dark matter halos with luminous galaxies. More specifically, it describes the bias between galaxies and dark matter by specifying (a) the probability P(N|M) that a halo of → virial mass M contains N galaxies of a particular class and (b) the relative spatial and velocity distributions of galaxies and dark matter within halos.
→ halo; → occupation; → distribution.
halo of galaxy
hâle-ye kakekašân (#)
Fr.: halo de galaxie
The diffuse, nearly spherical cloud of stars and → globular cluster s that surrounds a → spiral galaxy.
halo of the Galaxy
hâle-ye kakekašân (#)
Fr.: halo de la Galaxie
The → halo of galaxy belonging to our → Milky Way.
Fr.: population du halo
Old stars with very low metallicities (→ metallicity) found in the → halo of the Galaxy. Also called → population II star.
→ halo; → population.
halqe-ye hâlé, ~ hâlevâr
Fr.: anneau de halo
A faint, wide ring around → Jupiter that has the shape of a doughnut. It is about 22,800 km wide and about 20,000 km thick. This ring starts at 100,000 km from the center of Jupiter. The outer edge of the Halo merges into the → Main ring.
A member of a group of five chemical elements having closely related and similar properties. The halogens are: fluorine, chlorine, iodine, bromine, and astatine. They make up Group 17 of the → periodic table and can be found on the left-hand side of the → noble gases.
From Gk. halo- prefix from Gk. hals "salt" + → -gen.
Fr.: halo hydrostatique
A model of the → Milky Way galaxy in which the → Galactic halo (composed of → gas, → magnetic fields, and → cosmic rays) is assumed to be in → hydrostatic equilibrium. Parker (1966) presented the first study of stability considerations between gas, magnetic fields and cosmic rays in an equilibrium configuration. He found that it is difficult to maintain a stable configuration due to magnetohydrodynamic self-attraction (→ Parker instability). Subsequent works taking into account turbulent motions showed that turbulent pressure can mitigate the influence of Parker instabilities. This enabled new attempts to find conditions under which a stable equilibrium configuration of the Galaxy could exist.
→ hydrostatic; → halo.
Fr.: halo massif
Spheroidal distribution of dark matter surrounding a galaxy.
hâle-ye mâh (#)
Fr.: halo de la lune
Same as → lunar halo.
A class of molecules that contain at least one → halogen atom bonded to → carbon. Organohalogens are abundant on the Earth where they are mainly produced through industrial and biological processes. They have been proposed as → biomarkers in the search for life on → exoplanets. Simple halogen hydrides have been detected in → interstellar medium sources and in → comets. → Methyl chloride (CH3Cl), the most abundant organohalogen in the Earth's atmosphere, has both → natural and → synthetic production pathways (Fayolle et al., 2017, Nature Astronomy 1, 703).