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

A hypothetical weakly-interacting → boson of small mass required by models of → particle physics in order to solve the strong CP problem and explain a number of observed astrophysical/cosmological phenomena, including → dark matter, and the dimming of → type Ia → supernovae (→ accelerating Universe). Photons traveling in the → intergalactic medium would in part turn into axions in the presence of magnetic fields. The transformed photons are not detected on Earth and therefore supernovae would appear fainter even if the Universe is not accelerating.

Axion, first coined by Frank Wilczek (2004 Nobel Prize in Physics) apparently after a brand of washing detergent! The reason seems to be the idea that the particle will iron out a wrinkle in the → standard model of fundamental particles and forces while solving the problem of the Universe's → missing mass.

1) One of the principal lines through the center of a figure or a solid, especially, the line which divides the figure or solid symmetrically.
2) A fixed line along which distances are measured or to which position are referred.

L. axis "axle, pivot," akin to O.E. eax "axis, axle," Gk. axon "axle," Skt. aksa- "axle, axis, beam of a balance;" PIE base *aks- "axis."

Âsé, from Pers. dialects: Qâyeni asak "the shaft connecting the plough to the yoke," Lori esi "a pillar (used to put up a tribal tent)," variants hosi, hosin, Tabari âssen "the foot of a door on which it turns," cf. Skt. īṣā- "pole or shafts of a carriage or plough," Av. aêša "the two shafts," Mod.Pers. xiš "plough(share)," Gk. oiax "handle of rudder, tiller, helm," PIE base *ei-, *oi- "pole, thill."

Same as → rotation axis and → rotational axis.

→ axis; → rotation.

Having → axisymmetry.

Same as → axial symmetry.

The → angular distance from the → North point eastward to the intersection of the → horizon with the → vertical circle passing through the object. Azimuth is 0° for an object due north, 90° due east, 180° due south, and 270° due west. → Altitude and azimuth constitute the → horizon coordinate system.

From O.Fr. azimut, from Ar. as-sumut (السمت) "the directions, ways," pl. of as-samt "the direction, way."

Sugân, from su "direction" + -gân direction suffix.

One of great circles of the → celestial sphere which passes through the → zenith, → nadir, and the star, cutting the horizon at right angles. Same as → vertical circle.

→ azimuth; → circle.

Or, or pertaining to an → azimuth.

→ azimuth + → -al.

In → spherical coordinates, an angle measured from the x-axis in the xy-plane.

Azimuthal, adj. from azimuth; → angle.

In the → solar dynamo model, a magnetic field that points from east to west or vice-versa.

→ azimuthal; → magnetic; → field.

A map projection on which the → azimuths of all points are shown correctly with respect to the center. A plane tangent to one of the Earth's poles is the basis for polar azimuthal projection.

→ azimuthal; → projection.

In quantum mechanics, a quantum number that distinguishes the different shapes of the orbitals.

Azimuthal, adj. from → azimuth; → quantum number.