cloverleaf quasar (H1413+117)
kuâsâr-e barg-e šabdar
Fr.: quasar du trèfle à quatre feuilles
A bright → quasar whose image is split into four spots due to → gravitational lensing (Magain et al. 1988, Nature 334, 325). The four images of comparable brightness all lie within 0.7 arc seconds of the image center. The quasar has a → redshift of 2.56, corresponding to a distance of about 11 billion → light-years. Observations indicate that the lensing galaxy is located approximately at the geometrical center of the four images. A firm spectroscopic redshift of the lens has yet to be obtained; however, a → cluster of galaxies at a redshift of z = 1.7 has been suggested to account for the lensing of this system. H1413+117 was the first quasar to be detected in the → submillimeter wave → continuum and in → carbon monoxide emission.
So named because of the optical image; → clover; → leaf; → quasar.
kuâsâr-e maqzé ciré
Fr.: quasar dont l'émission de cœur domine
A → radio-loud quasar in which the central source is enhanced by → relativistic beaming and characterized by a → flat → spectrum. It has been conjectured that this phenomenon is an → orientation effect. If a radio-loud quasar is seen along its → jet, it will appear as a core-dominated source. See also → lobe-dominated quasar.
kuasâr-e lap ciré
Fr.: quasar à lobes dominants
A → radio-loud quasar in which the lobes dominate the whole emission. It has been conjectured that this phenomenon is an → orientation effect. If the → jet is close to the plane of the sky, the lobes will dominate. See also → core-dominated quasar.
A → binary system where an ordinary star orbits around a → neutron star or a → stellar-mass black hole that accretes the outer layers of the star's atmosphere. The accreted material falling on the → compact object warms up drastically and emits huge amounts of energy as → X-rays. The → accretion disk that emits this radiation also produces → relativistic jets of → plasma along the rotation axis of the compact object. The jets of material exhibit superluminal motion and resemble those emitted from → quasars, but on scales millions of times smaller. The first microquasar, 1E1740.7-2942, was discovered by F. Mirabel et al. 1992, Nature, 358, 215.
1) A → quasar of lesser power compared to
ordinary quasars hypothesized to exist at early cosmic times. According to some models,
the Universe was reionized by a population of miniquasars
powered by → intermediate-mass black holes.
optically violent variable (OVV) quasar
kuâsâr-e vartande-ye nurâné surâ
Fr.: quasar variable optiquement violent
A member of a small subset of quasars consisting of bright radio galaxies whose flux of visible light output can vary by as much as 50% in a single day.
kuâsâr (#), setârevaš (#)
An compact, extragalactic object which is highly luminous and looks like a star. Their redshifts can be large and their brightness varies. Quasars have an intrinsic luminosity which can reach some 100 times that of bright galaxies. They are thought to be active galactic nuclei with a size a little larger than the solar system. The first quasar to be identified as such, in 1963, was the radio source 3C 273 at a redshift of 0.158. With its 13th magnitude, it is the optically brightest quasar as observed from Earth. Some quasars are strong radio sources.
From quas(i) + (stell)ar (object).
kuâsâr-e râdioyi-ye xorušân
Fr.: quasar puissant en radio
A quasar that has the same characteristics as a → radio-quiet quasar with the addition of having strong radio emissions.
→ radio; loud, from O.E. hlud "making noise;" cf. M.Du. luut, Du. luid, O.H.G. hlut, Ger. laut "loud;" → quasar.
Kuâsâr, → quasar; râdioyi, adj. of → radio; xorušân "shouting aloud, roaring," from xorušidan "to shout, cry aloud, roar;" Mid.Pers. xrôšitan "to shout."
kuâsâr-e râdioi-ye ârâm
Fr.: quasar faible en radio
A type of quasar with weak radio emission. These types of quasars have strong emissions in both the optical and X-ray spectra. Within the optical spectrum, both broad and narrow emission lines are present. Their host is usually an elliptical galaxy, but less commonly, it might be a spiral. → radio-load quasar.
→ radio; quiet, M.E., from O.Fr. quiete, from L. quies (genitive quietis) "rest, quiet;" → quasar.
Kuâsâr→ quasar; → radio; ârâm "quiet" (Mid.Pers. râm "peace," râmenidan "to give peace, pleasure," râmišn "peace, pleasure;" Av. ram- "to stay, rest;" cf. Skt. ram- "to stop, stand still, rest, become appeased;" Gk. erema "quietly, gently;" Goth. rimis "rest;" Lith. rãmas "rest").