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

The point in the → Galactic plane that lies directly opposite the → Galactic center. It lies in → Auriga at approximately R.A. 5h 46m, Dec. +28° 56'; the nearest bright star to it is → Alnath in → Taurus.

Anticenter, from → anti- + → center.

Pâdmarkaz, from pâd-, → anti-, + markaz, → center.

The point on an elliptic orbit at the greatest distance from the principal focus or center of attraction.

Apocenter, from → apo- + → center.

Apâmarkaz, apâkayân, from apâ-, → apo-, + markaz or kayân, → center.

The center of mass of a system of bodies.

From Gk. barus "heavy," → bar, + → center.

Gerânigâh, from gerâni "weight;" cognate with Gk. barus, → bar, + gâh "place."

1) The point that is equidistant from all the points on a circle or sphere.
2a) To place in or on a center.
2b) Telescope: To move a telescope in order to place the object of interest on the center of the field. → center of attraction, → center of gravity, → center of inertia, → center of mass, → center wavelength, → anticenter, → apocenter, → barycenter, → optical center, → pericenter.

M.E. centre, from O.Fr. centre, from L. centrum "center," originally fixed point of the two points of a compass, from Gk. kentron "sharp point, goad," from kentein "stitch," from PIE *kent- "to prick."

Markaz "center," from Ar.; kayân, Mod.Pers. "the point made by the compasses, that is the center of a circle" [Dehxodâ]; markazidan, infinitive from markaz, → center, + -idan infinitive suffix.

A point toward which a force on a body is always directed.

→ center; → attraction.

A fixed point in a body through which the resultant force of gravitational attraction acts. Same as → center of mass, → center of inertia, → centroid.

→ center; → gravity.

Gerânigâh, from gerâni→ gravity + -gâh "place."

Same as → center of gravity, → center of mass, → centroid.

→ center; → inertia.

Same as → center of gravity, → center of inertia, → centroid, and → barycenter.

→ center; → mass.

Center of a filter passband measured at 50% of peak transmittance.

→ center; → wavelength.

In a triangle, the point where the perpendicular bisectors of the triangle's sides converge.

→ circum-; → center.

1) To come or go in.
2) To put in or insert. See also → entrance, → entry.

M.E. entren, from O.Fr. entrer, from L. intrare "to enter," from intra "within," → inter-.

Darâmadan, from dar, → in-, + âmadan, "to come," → egress; darâyidan, from dar- "in," + ây preset stem of âmadan, → assembly, + -idan infinitive suffix; darâyândan transitive of darâyidan.

The center of an → excircle.

→ ex-; → center.

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.

1) The rotational center of the → Milky Way galaxy located in the direction of the → Sagittarius constellation at a distance of 7.62 ± 0.32 kpc (2005, ApJ 628, 246). Its equatorial coordinates (J2000 epoch) are: R.A. 17h45m40.04s, Dec. -29° 00' 28.1''. The Sun orbits around the Galactic center once every 200 million years at a speed of 220 km per second. It is believed that there is a → supermassive black hole at the Galactic center.
2) The innermost region of a → spiral galaxy characterized by high number of stars per unit volume. The center may contain a → supermassive black hole.

→ galactic; → center.

One of the three massive clusters located toward the → Galactic center: → Quintuplet cluster, → Arches cluster, → Central cluster. Heavily extinguished by the presence of dust clouds and only accessible at infrared (and longer) wavelengths or in X-rays, each of these clusters has a population of more than a hundred → massive stars. The three clusters are similar in most respects, each containing about 10⁴ solar masses in stars. The Arches cluster is younger than the two others.

→ galactic; → center; → cluster.

In the → epicyclic theory of → galactic rotation, the center of the → epicycle.

→ guide; → center.

Of a thin lens, a point situated at the geometrical center of the lens, through which an incident ray passes without being deviated.

→ optical; → center.

Of a triangle, the point where the three → altitudes of the → triangle converge.

→ ortho-; → center.

The point in the orbit of one component of a binary system which is closest to the center of mass of the system; opposite of → apocenter.

→ peri- + → center.

The celestial coordinates of the center of the field of an astronomical photographic plate.

→ plate; → center.