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

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.

An equation for a curve written in terms of the → polar coordinates.

→ polar; → equation.

Solar faculae occurring in regions of high heliographic latitudes. They are smaller than the main-zone faculae; their shape is point-like or oval. Their lifetimes range from a few minutes to some hours, but the decisive difference from the main-zone faculae lies in their activity cycle. When spots and faculae of the main zone are at minimum, the polar faculae have their maximum activity, and vice versa.

→ polar; → facula.

A molecule in which the centers of positive and negative charge distribution do not converge and therefore has a mostly positive charge on one side and a mostly negative charge on the other. Different atoms around a central atom will always be polar molecules. Some polar molecules are H₂O, HF, COS, and CH₃Cl. Polar molecules are characterized by a → dipole moment.

→ polar; → molecule.

The irregularly varying motion of the Earth's pole of rotation with respect to the Earth's crust.

→ polar; → motion.

In polar regions, the portion of the year when the Sun does not rise above the horizon. Its length changes from twenty hours at the Arctic/Antarctic Circle (latitude 66°33' N or S) to 179 days at the North/South Pole.

→ polar; → day.

A spacecraft orbit that passes over, or close to, the geographic poles of the Earth or some other solar system object.

→ polar; → orbit.

A satellite that revolves around the Earth in an almost north-south orbit, passing close to both poles. The orbits are sun synchronous, allowing the satellite to cross the equator at the same local time each day. These satellites orbit at a height of 830-880 km and take about 100 minutes to complete a turn around the Earth.

→ polar; → orbit; → satellite.

A coronal feature of the Sun, which appears as long, thin streamers that project outward from the Sun's north and south poles

→ polar; → plume.

1) The → solar wind occurring at high latitudes during low → solar activity as a fast (around 750 km s^-1) and relatively steady flow. A remarkable feature of the polar wind is the ubiquitous presence of an intense flow of → Alfvénic fluctuations.
2) One of the two main wind components in → B[e] stars. The pole is hotter than the equator due to the → gravity darkening effect leading to a relatively fast, low-density wind driven by Fe IV lines. The other component is the → equatorial wind. The mechanism put forward to explain this wind morphology is the rotationally induced → bistability mechanism.
3) An extremely cold wind blowing from the north or south polar regions of the Earth.

→ polar; → wind.

Of or relating to → polarimetry.

→ polarimetry; → -ic.

The measurement of the → polarization state of light, usually through the use of a polarimeter.

From polari, from → polarization + → -metry.

The brightest star associated with the → north celestial pole. Polaris, also called the Pole Star, is a → triple system lying at about 433 → light-years (133 → parsecs) from the Earth. It is not exactly located on the Earth → rotation axis, because an → angular distance of 42 arc-minutes (about 1.4 lunar diameter) separates it from the true north pole. The main star, Polaris Aa (→ visual magnitude about 2), is a variable → pulsating star of type → Cepheid. It is a hot, blue F7 Ib → supergiant star having a → luminosity about 1,260 times that of the Sun. It has a mass of 5.4 Msun, a radius of 37.5 Rsun, and a → surface temperature of 6,015 K. The close companion Ab (apparent magnitude 9.2) is only 0''.17 (about 18.5 → astronomical units) from Polaris A. It was discovered in 1929 through examining the spectrum of Polaris A. It orbits Aa every 29.59 years. Ab is a → main sequence star of → spectral type F6 V. It has a mass of 1.26 Msun, a radius of 1.04 Rsun, and a luminosity of 3 Lsun. The third component, Polaris B (visual magnitude 8.7), is separated from A by 18.2 arc sec, corresponding to approximately 2,400 AU. It was first noticed by William Herschel in 1780. Polaris B is a main sequence star of type F3 V with a mass 1.39 Msun, a radius 1.8 Rsun, a luminosity of 3.9 Lsun, and a surface temperature of 6,900 K. Due to the → precession of equinoxes, the direction that Earth's axis points at changes slowly with time. Hence, Polaris has not always been, nor will it always be, the Pole Star. Polaris is actually drawing closer to the pole and in 2100 it will be as close to it as it ever will come, just 27.15 arc-minutes or slightly less than the Moon's apparent diameter. It will continue its reign as the North Star for many centuries to come. Historically, around 400 B.C., during Plato's time the nearest star to the Pole star was → Kochab (β Ursae Minoris). Some 4,600 years ago, when the Egyptians constructed the Pyramids, the Pole star was → Thuban (α Draconis). In 2,000 years the star → Errai (γ Cephei) will become the Pole Star. And around the year 14,000, Earth's axis will point reasonably close to the star → Vega, the fifth brightest star in the sky.

Mod.L. short for stella polaris "the pole star," → polar.

Setâre-ye qotbi "polar star," from setâré, → star, + qotbi, → polar.
Jodey, from Ar. Judaiy.
Mix-e gâh, Mid.Pers. name of the star, literally "the nail (peg) of time/place," from mix, → nail, + gâh "time; place," → origin.