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

The first → asteroid found to have an orbital → semi-major axis of less than one → astronomical unit. Discovered by the American woman astronomer Eleanor F. Helin (1932-2009) in 1982, it is the prototype of the → Aten asteroids.

Named after Aten, the Egyptian god of the solar disk.

A → tensor of → weight  → zero.

→ absolute; → tensor.

1) General: A device or a set of wires that receives or sends out radio signals.
2) In radio astronomy, the major dish-like component or wired structure used to collect radio signals.

L. antenna "sail yard," the long yard that sticks up on some sails, of unknown origin, perhaps from PIE base *temp- "to stretch, extend." In this sense, it is a translation of Gk. keraiai "horns" (of insects).

Âten, from Fr. antenne, from L. as above.

A measure of the directivity of a radio telescope. It is the ratio of the amount of power received in the direction the dish is pointing to the smaller amount of power from other directions in the sidelobes.

→ antenna; → gain.

A three-dimensional section of the → radiation pattern ofa directional antenna, bounded by one or more cones of nulls or by regions of diminished irradiance.

→ antenna; → lobe.

The response of an antenna to incident radiation as a function of the direction of incidence of the radiation. A generic antenna pattern consists of a → main lobe and a number of smaller → side lobes. Also called → radiation pattern.

→ antenna; → pattern.

In radio astronomy, a measure of the power absorbed by the antenna. In an ideal, loss-free radio telescope, the antenna temperature is equal to the brightness temperature if the intensity of the received radiation is constant within the main lobe. → antenna; → temperature.

antenna; → temperature.

The pair of colliding galaxies NGC4038 and NGC4039 and the long arcing insect-like "antennae" of luminous matter revealed by optical telescopes. The "antennae" are believed to have been produced by the collision between the galaxies that began about 100 million years ago and is still occurring. The Antennae Galaxies, about 60 million → light-years from Earth, lie in the constellation → Corvus.

Antennae, plural of → antenna; → galaxy.

Kahkešânhâ, plural of kahkešân→ galaxy; šâxak "insect antenna," from šâx "horn" (Mid.Pers šâk, cf. Skt. sakha- "a branch, a limb," Arm. cax, Lit. šaka, O.S. soxa, PIE *kakhâ "branch") + -ak suffix denoting relation, affinity, similarity (as in dastak, pos(tak, pas(mak, xarak, nâxonak, mus(ak, eynak);

A member of a class of → near-Earth asteroids with → perihelion distances between 0.983 and 1.0 → astronomical units. It is estimated that 6% of the total number of NEAs are Atens.

→ Aten; → asteroid.

1) To pay attention.
2) To be present at.

M.E. atenden, from O.Fr. atendre "to expect, wait for, pay attention," from L. attendere "give heed to," literally "to stretch toward," from → ad- "to" + tendere "stretch," → tension.

Âtânidan, from prefix â- + tân, from tan-, tanidan "to spin, twist, weave" (cf. tân "thread, warp of a web," variants târ "thread, warp, string," tâl "thread" (Borujerdi dialect), tur "fishing net, net, snare"); Mid.Pers. tanitan; Av. tan- to stretch, extend;" cf. Skt. tan- to stretch, extend;" tanoti "stretches," tantram "loom;" tántra- "warp; essence, main point;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch;" Lith. tiñklas "net, fishing net, snare;" PIE base *ten- "to stretch."

1) The act or state of attending.
2) The act or state of going to or being present at a place or event.
3) The persons or number of persons present at a particular place or event.

→ attend; → -ance.

A person who is present at a specific time or place.

From → attend + suffix -ee

Âtângar agent noun from → attend; pârgertandé agent noun from pârgertidan, → participate.

1) The act or faculty of attending, especially by directing the mind to an object.
2) Observant care; consideration (Dictionary.com).

→ attend; → -tion.

1) Characterized by or giving attention; observant.
2) Thoughtful of others; considerate; polite; courteous (Dictionary.com).

→ attend; → -ive.

1) To reduce in force, value, amount, or degree. → attenuation, → attenuation factor.
2) To reduce the amplitude of an electrical signal with little or no distortion.

L. attenuatus, p.p. of attenuare "to make thin," from → ad- "to" + tenuare "make thin," from tenuis "thin;" cf. Gk. tanaos "thin, slender, elongated;" Skt. tanuka-, tanu- "thin;" Av. tan- "to stretch;" Pers. tonok "thin," as below; O.Ir. tanae "delicate, thin;" O.H.G. dunni "thin."

Tonokidan, from tonok "thin, slender, slight, tender, delicate" + -idan, infinitive suffix. Tonok, from Mid.Pers. tanuk, Av. root tan- "to stretch, extend," cognate with L. tenuis, as above.

The falling off of the energy density of radiation with distance from the source, or with passage through an absorbing or scattering medium.

Verbal noun of → attenuate.

The fraction of a beam of → X-rays or → gamma rays that is absorbed or scattered per unit thickness of the → absorber. The linear attenuation coefficient, denoted by the symbol μ, appears in the equation I(x) = I₀e^-μx, where I(x) is the intensity at depth of x cm and I₀ is the original intensity.

→ attenuation; → coefficient.

The ratio of the radiation intensity after traversing a layer of matter to its intensity before.

→ attenuation; → factor.

The act or process of becoming bright or brighter. → limb brightening, → gravity brightening

Verbal noun of brighten, from → bright.

The branch of mathematics dealing with the differentiation of tensors.

→ calculus; → tensor.

Afmârik, → calculus; → tensor.