An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A suffix meaning "drawn, written," specialized in meaning to indicate the instrument rather than the written product of the instrument.

A suffix, from Gk. -graphos "(something) drawn or written, one who draws or writes," from graphein "to draw, write."

A suffix from the stem of negârdan, negâštan "to paint, write," → graph.

An adjective relating to → -graph.

→ -graph + → -ic.

A combining form denoting a process or form of drawing, writing, representing, recording, describing, etc., or an art or science concerned with such a process. Examples: geography; orthography; → photography; → radiography; → selenography; → tomography.

→ graph.

A combining form meaning "lover of, attracted to" that specified by the initial element.

-phile, also -phil, from M.L. -philus, from Gk. -philos, common suffix in personal names (such as Theophilos), from philos "loving, dear," from philein "to love," which is of unknown origin.

-dust, from dust "friend; lover;" Mid.Pers. dôst "friend;" O.Pers. dauštar- "friend;" Av. zaoša- "pleasure," zuš- "to like," zušta- "loved;" cf. Skt. jos- "to like, be pleased, enjoy," jósa- "satisfaction," jóstar- "loving;" Gk. geuomai "to taste;" L. gustare "to taste."

An → Apollo asteroid with unusual properties. Phaethon was discovered on October 11, 1983 using the → Infrared Astronomical Satellite. It is dynamically associated with the → Geminid meteor shower. Whereas most established → meteor shower parents are clearly → cometary in nature, the orbit of Phaethon is that of an → asteroid . Its → semi-major axis, → eccentricity, and → orbital inclination are a = 1.271 AU, e = 0.890, and i = 22.2, respectively, and the → Tisserand parameter with respect to → Jupiter is T_J = 4.5 (while the conventional → comets have T_J < 3). The → perihelion distance is remarkably small, q = 0.14 AU. Phaethon is roughly 5 km in diameter. Not to be confounded with → Phaeton.

Named after the Greek myth of Phaethon, son of the Sun god Helios, due to its close approach to our Sun.

The → locus of the intersection of input and output → conjugate rays in an optical system satisfying the → Abbe sine condition.

→ Abbe sine condition; → sphere.

The brightest star in the constellation → Eridanus. A → subgiant of → spectral type B5; apparent visual magnitude 0.5, about 140 → light-years distant (other names: HR 472, HD 10144). Recent interferometric observations show it to have a flattened shape imposed by fast rotation.

Achernar, from Ar. Axir an-Nahr "end of the river," from axir "end" + nahr "river".

Âxer-e nahr, from Axir an-Nahr.
Rudpâyân "river's end," from rud "river," → Eridanus, + pâyân "end".

Same as the → Sedov-Taylor phase.

→ adiabatic; → phase.

Meteo.: The wind component deviating from the → geostrophic wind in the absence of the → geostrophic balance. In other words, ageostrophic wind is the difference between the true wind and the geostrophic wind.

From negation prefix → a- + → geostrophic; → wind.

The brightest star in → Cepheus and a → subgiant star of apparent visual magnitude 2.44. Its → spectral type is A7 and distance 49 → light-years.

Alderamin, from Ar. al dhirâ' al-yamin "right arm" (of Cepheus), from Ar. dhirâ' "arm" + yamin "right".

Zerâ'-e Yamin, from Ar. al dhira al-yamin.

1) The first letter of the Hebrew alphabet (ℵ).
2) A → cardinal number representing an uncountable set. For example, ℵ₀ (pronounced aleph-null, aleph-nought, or aleph-zero) is the smallest infinite cardinal and ℵ₁ is the smallest cadinal larger than ℵ₀.

Hebrew and Phoenician letter, from Semitic languages.

The first letter of the Greek alphabet (A, α).

Gk. alpha, from Hebrew or Phoenician → aleph.

An annual → meteor shower that takes place within the boundaries constellation → Capricornus near the star named Alpha. The meteor shower is visible between July 03 and August 15 with the peak occurring on July 30. Alpha Capricornids meteors are bright and often include spectacular colorful → fireballs.

→ alpha; → Capricornus.

Brightest star in the constellation → Centaurus (V = -0.01 magnitude) and third brightest star in the sky; also known as → Rigil Kent. It is a main-sequence star of the same spectral class (G2 V) as the Sun. Actually, Alpha Centauri is a triple-star system, the components being designated A, B, and C. The component C is also called → Proxima Centauri because it is the closest star to the Earth (other than the Sun), at a distance of 4.22 → light-years, but it is too dim to be seen with the naked eye. Components A and B are currently about 4.36 light-years away.

Alpha (α), a Gk. letter of alphabet used in the → Bayer designation; Centauri, genitive of → Centaurus.

A system of three stars, the → close binary Alpha Centauri A (→ spectral type G2 V) and Alpha Centauri B (K1 V), and a small and faint → red dwarf, Alpha Centauri C (M6 Ve), better known as → Proxima Centauri. To the unaided eye, the two main components (AB) appear as a single object with an → apparent visual magnitude of -0.27, forming the brightest star in the southern constellation → Centaurus and the third brightest star in the night sky, after → Sirius and → Canopus. The individual visual magnitudes of the components A, B, and Proxima are +0.01, +1.33, and +11.05, respectively. The masses of A and B are 1.100 and 0.907 Msun, respectively. Their → effective temperatures are (A) 5,790 K and (B) 5,260 K; their luminosities (A) 1.519 Lsun and (B) 0.500 Lsun. The binary members are separated in average by only 23 → astronomical units. They revolve around a common center of mass with a period of about 80 years. Both have a distance of 4.37 → light-years. Proxima Centauri, lying about 15,000 AU apart from AB, is → gravitationally bound to them. It has a mass of 0.1 Msun, a radius of 0.1 Rsun, a luminosity of about 0.001 Lsun, and an → effective temperature of ~ 3,000 K.

→ alpha; → Centaurus; → system.

The radioactive transformation of a nuclide by alpha-particle emission. Also called alpha disintegration.

→ alpha; → decay.

A simple → accretion disk model in which the → angular momentum is transported outward by action of some kind of → viscosity. In this model, first proposed by Shakura & Sunyaev (1973), the turbulent kinematic viscosity is given by ν = α c_s H, where α is a parameter, c_s the sound speed in the medium, and H → scale height. The α parameter controls the amount of → turbulence in the medium whose H and c_s are upper limits for → mixing length and turbulent speed, respectively. Values of α = 10^-3 to 10^-2 yield evolution → time scales that are broadly consistent with the ages inferred for → T Tauri stars. A weak point of this model is the arbitrariness of the choice of the parameter α, which reflects the lack of a rigorous theory of turbulence.

→ alpha, the parameter name; → disk; → model.

The → mechanism that imparts or transfers power to a → telescope so that it can move along the → right ascension direction. See also → tacking.

→ alpha, → right ascension; → drive.

In the → solar dynamo model, the process whereby the → azimuthal magnetic field transforms into a → meridional magnetic field due to the interaction of → convection and → differential rotation. See also → omega effect.

→ alpha; → effect.

A → chemical element synthesized in → massive stars by → alpha particle capture leading to iron before the advent of a → type II supernova. Stable alpha elements are: C, O, Ne, Mg, Si, S, Ar, Ca.

→ alpha; → element.