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

A combining form (also -gene) used in the formation of compound words, meaning: 1) "one that generates:" → hydrogen, → halogen, andogen, and so on. 2) "one that is generated, produced:" exogen, cultigen, phosgene.

From Fr. -gène "producing," Gk. -genes "produced, born," → generate;

A combining form of genesis.

From L. genesis, from Gk. genesis "origin, generation," from gignesthai "to be born," related to genos "race, birth, descent," cognate with Pers. zâdan "to bring forth, give birth," → generate.

A combining form meaning "angled, angular," used in the formation of compound words. → heptagon, → hexagon, → polygon.

From Gk. gonia "angle," related to gony "knee;" L. genu "knee;" Mod.Pers. zânu "knee;" Av. žnav-, žnu- "knee;" Skt. janu-; PIE base *g(e)neu-.

From bar "side; breadth; breast," variant var (Mid.Pers. var "breast;" Av. vouru "wide, broad, extended" (vourucašāni- "looking far"), related to varah- "breast;" cf. Skt. urú- "wide, broad," úras- "breast;" Gk. eurus "wide, broad;" PIE base uer-, ueru-s"wide, broad"); -guš "corner, angle," Mid.Pers. gošak "corner."

A combining form meaning "something drawn, written" (diagram, spectrogram, oscillogram).

From Gk. -gramma, combining form of gramma "something written or drawn," → graph.

-Negâšt, from negâšt "drawn, written;" p.p. of negâštan, negârdan "to paint, write," → graph.

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 conspicuous band of molecular → CH (methylidine) at 4300 Å, which is present in the spectra of late-type G-K stars.

G refers to → G type stars in the spectra of which this feature is strong. → band.

Waves trapped inside stars, whose restoring force is the → buoyancy. Same as → gravity mode. See also: → oscillation modes; → p mode; → f mode.

g referring to gravity; → mode.

The → Saturn's ring, with a width of 8,000 km, lying before the → F ring, at 164,000-172,000 km from the center of Saturn.

→ ring.

A member of a class of stars to which the Sun belongs. The G-type stars on the → main sequence have → surface temperatures of 5,300-6,000 K and therefore appear yellow in color. G type → giant stars (such as → Capella) are almost 100-500 K colder than the corresponding main sequence stars. G type → supergiants have temperatures of 4,500-5,500 K. The spectrum of early type G stars, such as the Sun (G2), is dominated by ionized lines of calcium (→ H and K lines, mainly) and neutral metals. In later type G stars the molecular bands of → CH molecules and → CN molecules become visible. The main sequence and giant stars have masses of ~ 1 solar mass, while the supergiants are of ~ 10 solar masses. The luminosities of G-type giants are almost 30-60 times greater than that of the Sun, whereas the supergiants are 10,000-30,000 times more luminous.

G, from the → Harvard classification; → star.

A yellowish star whose surface temperature is about 6000 K and its spectrum is dominated by H and K lines of ionized calcium (Ca II 3968 Å and 3934 Å).

G from the alphabetical sequence of spectral types; → type; → star.

A relatively uncommon → carbonaceous carbonaceous asteroid whose spectrum contains a strong → ultraviolet  → absorption feature below 0.5 μm (→ Tholen classification). In the → SMASS classification it corresponds to the Cg and Chg types , depending on the presence or absence (respectively) of the absorption feature at 0.7 μm. The most remarkable "asteroid" in this type is → Ceres (now classified as a → dwarf planet).

→ type; → asteroid.

Same as → G star.

→ G star; → type.

A → European Space Agency  → astrometry mission launched on 19 December 2013. Gaia's goal is to create the largest and most precise three-dimensional chart of the → Milky Way galaxy by providing unprecedented positional (position on the sky and distance to the Sun) and annual → proper motion measurements for about one billion stars in our Galaxy and throughout the → Local Group. Moreover, the third component of the velocity, the → radial velocity, will be obtained for all stars down to V = 17 mag. Similarly, multi-color photometry will be carried out on all stars down to V = 20 mag. Gaia will achieve the planned astrometric requirements by repeatedly measuring the positions of all objects down to V = 20 mag with final accuracies of about 20 microarcsec at 15 mag. It will provide distances accurate to 20% as far as the → Galactic Center. The satellite is expected to be launched in 2012 and be placed in a → Lissajous orbit around the Sun-Earth → Lagrangian point L2. Gaia is a much more advanced version of the → Hipparcos mission.

Initially, GAIA was the short for Global Astrometric Interferometer for Astrophysics. Although subsequently the interferometer option was abandoned, the acronym was maintained in lower case.

1) A measure of the → amplification of an electronic device, usually expressed as the ratio of → output power to → input power.
2) → antenna gain.

From M.Fr. gain, from O.Fr. gaaigne, from guaaignier "to obtain," from Germanic *waidanjan "to hunt, plunder," also "to graze, pasture," from P.Gmc. *wartho "hunting ground" (cf. Ger. weide "pasture, pasturage"); PIE base *weiə- "to go after something, strive after."

Bahré, from bahr "part, portion, share, lot;" Av. baxəδra- "portion," from bag- "to attribute, allot," → division.

1) Of or pertaining to a → galaxy.
2) Usually with capital G, pertaining to our galaxy, the → Milky Way.

Adjective of → galaxy.

The point in the → Galactic plane that lies directly opposite the → Galactic center. It lies in the constellation → Auriga at approximately R.A. 05h 46m, Dec. +28° 56'.

→ galactic; → anticenter.

An elongated bar-shaped structure composed of stars present in some spiral galaxies. About two-third of such galaxies contain bars that cross their centers. Bars, like → spiral arms, result from a → density wave in which stars take very elliptical orbits. They form when the → galactic disk dominates the → galactic bulge, → Ostriker-Peebles criterion. Bars play an extremely important role in a galaxy's evolution. The gravity from a bar is the mechanism that drives → interstellar gas from the outer parts of a → spiral galaxy inward toward the central regions, and into the galactic nucleus itself. This causes tremendous bursts of star formation. Therefore, a majority of massive stars are born in such starbursts in the nuclei of galaxies. Bars may also channel the material that falls into black holes within active galactic nuclei, releasing enormous power in radiation and particles from tiny regions at the centers of some galaxies. Bars disappear as galactic centers grow more massive (after some 2 to 8 Gyr).

→ galactic; → bar.

The central → galaxy bulge of the → Milky Way.

→ galactic; → bulge.