Fr.: mouvement de Chandler
Small-scale variations in the position of the Earth's geographical poles within an irregular circle of 3 to 15 metres in diameter. It seems to result from two nearly circular components, a seasonal variation in the mass distribution on the Earth (ice, snow, atmosphere) and movements of matter within the Earth.
Named after Seth Carlo Chandler (1846-1913), the American astronomer who discovered the phenomenon; → wobble.
Chandra X-ray Observatory
nepâhešgâh-e partowhâ-ye X-e Chandra
Fr.: Observatoire des rayons X Chandra
An astronomy satellite launched by NASA in 1999 July, specially designed to detect X-ray emission from very hot regions of the Universe such as exploded stars, clusters of galaxies, and matter around black holes. Chandra carries a high resolution mirror (aperture 1.2 m, focal length 10 m), two imaging detectors (HRC and ACIS), and two sets of transmission grating spectrometer (LETG and HETG). Important Chandra features are: an order of magnitude improvement in spatial resolution, good sensitivity from 0.1 to 10 keV, and the capability for high spectral resolution observations over most of this range. Chandra was initially given an expected lifetime of 5 years, but on 4 September 2001 NASA extended its lifetime to 10 years "based on the observatory's outstanding results." Among the results obtained using Chandra one can mention the spectacular image of the → supernova remnant Cassiopeia A. See also → X-ray astronomy.
Initially called Advanced X-ray Astrophysics Facility (AXAF), the satellite was renamed the Chandra X-ray Observatory in honor of Subrahmanyan Chandrasekhar, the 1983 Nobel Prize in Physics, → Chandrasekhar limit. Moreover, Chandra, or candra- means "moon" or "shining" in Skt., from cand- "to give light, shine;" cf. Gk. kandaros "coal;" L. candela "a light, torch," from candere "to shine;" → X-ray; → Observatory.
hadd-e Chandrasekhar (#)
Fr.: limite de Chandrasekhar
A limiting mass of about 1.44 Solar masses that the theory predicts a non-rotating → white dwarf can attain without collapsing to become a → neutron star or a → black hole. Over this → critical mass, the degeneracy pressure will be unable to bear the load of the bulk mass.
Named after Subrahmayan Chandrasekhar (1910-1995), Indian-born American astrophysicist who, with William A. Fowler, won the 1983 Nobel Prize for Physics for his research on white dwarfs; → limit.
1) The terminal part of the forelimb in humans and other primates.
M.E. O.E. hond, hand "hand; side; power;" cf. O.S., O.Fris., Du., Ger. hand, O.N. hönd, Goth. handus.
Dast "hand; strength; superiority;" Mid.Pers. dast; O.Pers. dasta-; Av. zasta-; cf. Skt. hásta-; Gk. kheir; L. praesto "at hand;" Arm. jern "hand;" Lith. pa-žastis "arm-pit;" PIE *ghes-to-.
A scholarly book on a specific subject that is conveniently handled.
Fr.: latéralité, manualité
1) A tendency to use one hand rather than the other.
razan-e dast-e cap
Fr.: règle de la main gauche
See → Fleming's rules.
capâl (#) , capdast (#)
Using the left hand with greater ease than the right.
razan-e dast-e râst
Fr.: règle de la main droite
See → Fleming's rules.
right-hand screw rule
razan-e pic-e rast-gard
Fr.: règle de la vis droite
A rule that gives the direction of the resultant vector in a → vector product: A x B = C. It is the direction of advance of a right-hand screw whose axis, held perpendicular to the plane of A and B, is rotated in the same sense that rotates the first-named vector (A) into the second-named vector B through the smaller angle.
râstâl, râstdast (#)
Using the right hand with greater skill or ease than the left.
Fr.: limite de Schönberg-Chandrasekhar
During the → main sequence stage, a star burns the hydrogen in its core and transforms it into helium. When the helium mass amounts to about 10% of the initial stellar mass, the star can no longer maintain the → hydrostatic equilibrium in its core; the star increases its volume and leaves the main sequence in order to become a → red giant.
Named after the Brazilian astrophysicist Mario Schönberg (1914-1990) and Subramahmanyan Chandrasekhar, → Chandrasekhar limit, who were the first to point out this limit and derive it (1942, ApJ 96, 161).
super-Chandrasekhar SN Ia
abar-now-axtar-e gune-ye Ia-ye abar-Chandrasekhar
Fr.: supernova de type Ia super-Chandrasekhar
A superluminous → Type Ia supernova which is characterized by a bright → light curve peak, a slow light curve evolution during the photospheric phase, and moderately low ejecta velocities. Modeling suggests ejecta masses far in excess of the → Chandrasekhar limit of mass for non-rotating → white dwarfs and the production of about 1.5 Msun of 56Ni. This precludes the interpretation of these events as thermonuclear explosions of Chandrasekhar-mass white dwarfs.