Fr.: nébuleuse de la Rosette
A giant H II region of about 1° in diameter, lying about 5000 light-years away in the Milky Way, the constellation → Monoceros. It is ionized by the cluster NGC 2244, a group of hot young stars at the center of the nebula. Also called M16, the brighter portions of the nebula have been assigned different NGC numbers: 2237, 2238, 2239, and 2246.
Rosette "a rose-shaped ornament," from Fr. rosette, from O.Fr. rosette, diminutive of rose "rose;" L. rosa, probably from Gk. wrodon (Aeolic), then rhodon, a loan from Iranian, as below; → nebula.
Miq, → nebula; golsân "resembling rose, flower," from gol "flower, rose," variants vard (sohre-vard "red rose"), Semnâni dialect vela "rose;" Mid.Pers. *vard, gul, loaned in Arm. vard and Ar. ward; Av. varəδa- "rose;" loaned in Gk. wrodon (Aeolic), then rhodon; + -sân "manner, semblance" (variant sun, Mid.Pers. sân "manner, kind," Sogdian šôné "career").
Fr.: Ross 128
A → red dwarf star of → spectral type M4. Other designations: Proxima Virginis, FY Virginis, GJ 447, HIP 57548, and LHS 315. With a distance of just 3.4 → parsecs, it is one of the brightest representatives of this subclass (V = 11.15, J = 6.51, H =5.95, K = 5.65 mag). It is the 13th closest (sub-)stellar system to the Sun, including → brown dwarfs. Ross 128 is moving toward us and will actually become our closest neighbor in just 71,000 years from now. Ross 128 has an → effective temperature, Teff = 3192, a mass of 0.168 Msun (→ solar mass), a → luminosity of 0.00362 Lsun (→ solar luminosity), a radius of 0.017 Rsun (→ solar radius), and a → metallicity [Fe/H] of -0.02. An Earth-sized → exoplanet, → R 128 b, orbits Ross 128 (Bonfils et al., 2017, arXiv:1711.06177).
Star number 128 in the → Ross Catalogue.
Ross 128 b
Ross 128 b
Fr.: Ross 128 b
An → extrasolar planet around the → red dwarf star → R 128. The → exoplanet orbits its star every 9.9 days. This Earth-sized world is expected to be temperate, with a surface temperature that may also be close to that of the Earth. Many red dwarf stars, including → Proxima Centauri, are subject to → flares that occasionally bathe their orbiting planets in deadly → ultraviolet and → X-ray radiation. However, it seems that Ross 128 is a much quieter star, and so its planets may be the closest known comfortable abode for possible life. Ross 128 b orbits 20 times closer than the Earth orbits the Sun. Despite this proximity, it receives only 1.38 times more irradiation than the Earth. As a result, Ross 128 b's equilibrium temperature is estimated to lie between -60 and 20°C, thanks to the cool and faint nature of its small red dwarf host star, which has just over half the surface temperature of the Sun.
The letter b, designates the first exoplanet discovered around → R 128.
Fr.: Catalogue de Ross
Ross, Frank E., 1926, "New proper-motion stars, (second list)", Astronomical Journal 36, 856.
Frank Elmore Ross (1874-1960) was the succeeded to E. E. Barnard at Yerkes Observatory. He inheriting Barnard's collection of photographic plates. Ross decided to repeat the same series of images and compare the results with a → blink comparator. He discovered 379 new variable stars and over 1000 stars of high proper motion.
Fr.: nombre de Rossby
A dimensionless number relating the ratio of inertial to Coriolis forces for a given flow of a rotating fluid. It is used in the study of atmospheric motions in planets. In case a small number is involved, cyclones and anticyclones are observed for low and high pressures. When it is large (Venus) the Coriolis force becomes negligible and atmospheric motions are barely affected by planetary rotation.
Named after Carl-Gustav Arvid Rossby (1898-1957), a Swedish-American meteorologist who first explained the large-scale motions of the atmosphere in terms of fluid mechanics; → number.
Fr.: paramètre de Rossby
The northward variation of the Coriolis parameter, arising from the sphericity of the Earth.
Fr.: onde de Rossby
A wave on a uniform current in a two-dimensional non-divergent fluid system, rotating with varying angular speed about the local vertical.
Rosseland mean opacity
kederi-ye miyângin-e Rosseland
Fr.: opacité moyenne de Rosseland
The → opacity of a gas of given composition, temperature, and density averaged over the various wavelengths of the radiation being absorbed and scattered. The radiation is assumed to be in → thermal equilibrium with the gas, and hence have a → blackbody spectrum. Since → monochromatic opacity in stellar plasma has a complex frequency dependence, the Rosseland mean opacity facilitates the analysis. Denoted κR, it is defined by: 1/κR = (π/4σT3) ∫(1/kν) (∂B/∂T)νdν, summed from 0 to ∞, where σ is the → Stefan-Boltzmann constant, T temperature, B(T,ν) the → Planck function, and kν monochromatic opacity (See Rogers, F.J., Iglesias, C. A. Radiative atomic Rosseland mean opacity tables, 1992, ApJS 79, 507).
Fr.: effet Rossiter-McLaughlin
A → spectroscopic phenomenon observed when either an → eclipsing binary's → secondary star or an → extrasolar planet is seen to → transit across the face of the → primary body. Because of the rotation of the star, an asymmetric distortion takes place in the → line profiles of the stellar spectrum, which changes during the transit. The measurement of this effect can be used to derive the → alignment of the → orbit of the transiting exoplanet with respect to the → rotation axis of the star.
Named after Richard Alfred Rossiter (1886-1977) and Dean Benjamin McLaughlin (1901-1965), American astronomers.
To turn around an axis. See also → revolve.
From L. rotare "to cause to spin, roll, move in a circle," from L. rota "wheel;" cognate with Pers. râh "way, path" (from Mid.Pers. râh, râs "way, street," also rah, ras "chariot;" from Proto-Iranian *rāθa-; cf. Av. raθa- "chariot;" Skt. rátha- "car, chariot," rathyā- "road;" Lith. ratas "wheel;" O.H.G. rad; Ger. Rad; Du. rad; O.Ir. roth; PIE *roto- "to run, to turn, to roll").
Carxidan "to rotate," from carx "every thing performing a circulatory motion; a wheel; a cart;" Mid.Pers. chr "wheel," Parthian cxr "wheel;" Ossetic calx "wheel;" Av. caxra- "wheel;" cognate with Skt. cakra- "wheel, circle; cycle," carati "he moves, wanders;" Gk. kyklos "circle, wheel," polos "axis of a sphere," polein "move around;" L. colere "to dwell in, to cultivate, move around," colonus "farmer, settler;" O.E. hweol "wheel;" Rus. koleso "wheel."
Fr.: en rotation
Capable of or having rotation.
rotating black hole
Fr.: trou noir en rotation
A black hole that possesses angular momentum, as first postulated by Roy C. Kerr in 1963. Opposite of a stationary black hole. → ergosphere.
setâre-ye carxân, ~ carxandé
Fr.: étoile en rotation
A star that has a non-zero → angular velocity. In a rotating star, the → centrifugal forces reduce the → effective gravity according to the latitude and also introduce deviations from sphericity. In a rotating star, the equations of stellar structure need to be modified. The usual spherical coordinates must be replaced by new coordinates characterizing the → equipotentials. See also → von Zeipel theorem.
The motion of a body about its axis.
Verbal noun of → rotate.
Fr.: axe de rotation
Fr.: courbe de rotation
A plot of the variation in → orbital velocity of stars and → interstellar matter with distance from the center of a → galaxy. A "flat" rotation curve indicates that the mass of the galaxy increases linearly with distance from its center. See also: farsi→ Keplerian rotation curve
Rotation; → curve.
Fr.: énergie de rotation
Fr.: fréquence de rotation
1) The number of rotations per unit time of a rotating object.
dowre-ye carxeš (#)
Fr.: période de rotation
The interval of time during which an object turns once about its axis.
Fr.: phase de rotation