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

The polarization of starlight caused by aligned → interstellar grains, so that initially → unpolarized light from a star is partially polarized by the time it reaches the Earth.

→ interstellar; → polarization.

Of an electromagnetic radiation, a → polarization in which the electric vibrations are confined to one plane along the direction of propagation. Also called → plane polarization. See also → circular polarization.

→ linear; → polarization.

Light exhibiting → linear polarization.

→ linearly; → polarized; → light.

The ability of a molecular entity to be distorted from its normal shape by an external → electric field. When a molecule is subjected to an electric field there is a small displacement of electrical centers which induces a dipole in the molecule. More specifically, the molecular polarizability α is defined as the ratio of the induced → dipole moment (p) to the local electric field (E) that produces this dipole moment: α = p/E (in cgse units).

→ molecular; → polaizable; → -ity.

A type of polarization in which the direction of polarization becomes reversed.

→ negative; → polarization.

A large area of the north polar region of Mars which is covered with alternating layers of water ice and dust. → South Polar Layered Deposits.

→ north; → polar; → layer; → deposit.

One of the largest coherent structures in the radio sky, projecting from the → Galactic plane at → Galactic longitudel ~ 20° and extending to a very high → Galactic latitudeb ~ +80°. It was first identified in low frequency → radio surveys in the 1950s. The spur is also prominent in → soft X-rays. Its origins and nature have long been debated. However, what causes this phenomena is not well understood. It may be due to a combination of → OB associations and → supernova explosions.

→ north; → polar; → spur.

In a → linearly polarized light, a plane perpendicular to the → plane of vibration and containing the direction of propagation of light. It is also the plane containing the direction of propagation and the magnetic vector (H) of the electromagnetic light wave.

→ plane; → polarization.

Same as → linear polarization.

→ plane; → polarization.

Light exhibiting → plane polarization. Same as → linearly polarized light.

→ plane; → polarized; → light.

1) Of or pertaining to the pole of any sphere, a magnet, an electric cell, etc.
2) A subclass of → cataclysmic variables, the prototype being AM Herculis. Polars are short-period systems in which a → late-type → main sequence star transfers mass to a highly magnetized → white dwarf. The strong magnetic field (10-70 million → gauss) prevents the formation of an → accretion disk, locks both stars in synchronous rotation and guides the accreting matter to accretion spots which are the source of intense X-ray radiation (material impacts on to the white dwarf where it is radiated away).

1) Adj. of → pole.
2) From polar(ization) + (st)ar, because of their → circularly polarized light.

The process or the state of making a → telescope's → polar axis → parallel to the → Earth's → rotation axis, that is with the → true North or → South  → celestial pole. When this is accomplished, the sky's motion can be cancelled out simply by turning the axis (either by hand or with a motor → drive) at the same rate as the rotation of the Earth, but in the opposite direction.

→ polar; → alignment.

The axis of an → equatorial mounting that is parallel to the Earth's axis, and consequently points to the celestial pole.

→ polar; → axis.

A chemical bond where the electrons are shared unequally between atoms. The atom that is more electronegative will pull the electrons closer to itself.

→ polar; → bond.

1) Either of the regions around the poles of the Earth that are permanently covered with ice.
2) Either of the two regions around the poles of the planet Mars, consisting of frozen carbon dioxide and water ice.
3) An area of a → pulsar's surface from where open magnetic field lines emanate.

→ polar; → cap.

An imaginary parallel circle on the celestial sphere or on the Earth at a distance of 23°.5 from either poles.

→ polar; → circle.

A coordinate system in which the position of any point (M) in a plane is specified by two coordinates: 1) ρ, which expresses the distance from a fixed point (the pole, denoted O), and 2) the number φ, which is the angle formed by the line segment OM and a fixed reference line passing through the pole.

→ polar; → coordinate.

An area in the Earth's → magnetosphere, where the → magnetosheath plasma has direct access to the → ionosphere.

→ polar; → cusp.

In polar regions, the portion of the year when the Sun is continuously in the sky. Its length changes from twenty hours at the Arctic/Antarctic Circle (latitude 66°33' N or S) to 186 days at the North/South Pole.

→ polar; → day.

The angular distance of an object from a celestial pole. It is equal to 90° minus the object's declination.

→ polar; → distance.