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

Meteo.: The point on the → celestial sphere that lies directly opposite the Sun from the → observer, observer, that is, on the line from the Sun through the observer. The antisolar point is the center of the rainbow, and can be easily found on a sunny day: it it located at the shadow of one's head; it is 180° away from the Sun. If the Sun is in the sky, the antisolar point is below the horizon. If the Sun has set, the antisolar point is above the horizon.

→ anti-; → solar; → point.

The duration of one rotation of the Earth on its axis (→ Earth's rotation), with respect to the → apparent Sun. It is measured by successive transits of the apparent Sun over the lower branch of a → meridian.

→ apparent; → solar day.

The time based on the motion of the → apparent Sun and kept by dividing the day into 24 equal hours.

→ apparent; → solar; → time.

Surrounding or revolving around the Sun, such as circumsolar space, circumsolar dust.

Circumsolar, from → circum- + → solar.

A period in the evolution of the → solar system when the planets and satellites were in the process of formation.

→ early; → solar; → system.

Electrons and atomic nuclei ejected by solar flares, travelling with velocities amounting to a fraction of the velocity of light, and energies mostly in the range 1-100 million → electronvolts (eV), but occasionally as high as 15 billion eVs. Also known as solar → cosmic rays.

Energetic, from Gk. energetikos, from energe-, → energy, + -tikos a suffix, equivalent in meaning to → -ic, occurring in adjectives; → solar; → particle.

Zarrehâ plural of zarré, → particle; xoršidi, → solar; kâružmand from kâruž, → energy, + -mand possession suffix.

Not belonging to the → solar system; outside, or originating outside, the solar system.

→ extra-; → solar.

A planet which belongs to a star other than → Sun, and therefore does not belong to our → solar system; same as → exoplanet.

→ extrasolar; → planet.

A → planatary system around a star other than the Sun. Same as → exoplanetary system .

→ extrasolar; → system.

A calendar in which the → solar year consists of 12 or 13 lunar → synodic months. Lunisolar calendars are → solar calendars, but use the lunar month as the basic unit rather than the → solar day. The 13th → embolismic month is to keep lunar and solar cycles in pace with each other. The reason is that the solar year has about 365 days, but 12 lunar months amount to 354 days, which is about 11 days short of a year. The most well-known lunisolar calendars are the Babylonian, Hebrew, and Chinese.

From luni-, from → lunar, + → solar; → calendar.

→ precession of the equator.

From luni-, from → lunar, + → solar; → precession.

The average length of the apparent solar day. In other words, the interval between successive transits of the mean Sun for a given observer.

→ mean; → solar; → day.

The time since the mean Sun crossed the meridian with 12 hours added to make the day begin at midnight.

→ mean; → solar; → time.

A NASA space mission launched on August 12, 2018 to study the outer corona of the Sun at very close distances. Parker Solar Probe is the first space mission to penetrate into solar corona as close as about 10 solar radii. It will approach the Sun to this distance 25 times. Approaching the Sun to such distances is a big technological challenge. The main goals of the mission are to answer these questions: Why is the solar corona so hotter than the solar surface? How is the solar wind accelerated? How are the energetic particles produced and transported?

Named after the physicist Eugene Newman Parker (1927-), who proposed the existence of the solar wind and did pioneering work for its interpretation.

A → solar eclipse when only the → penumbra of the Moon touches the Earth. The → umbra passes either just above the North Pole or just below the South Pole, missing the Earth.

→ partial; → solar; → eclipse.

Of or relating to an epoch earlier than the formation of the Sun.

→ pre-; → solar.

A → refractory → nanoparticle embedded in → meteorites and → interplanetary dust particles whose → isotopic ratios suggest formation earlier than the Solar System.

→ presolar; → grain.

Describing the conditions prior to the formation of the → solar system, or pertaining to the → protostar that became the → Sun.

→ proto- + → solar.

The abundance of a chemical element pertaining to the proto-→ solar nebula from which the → solar system was formed. → CI chondrite; → CAI meteorite.

→ protosolar; → abundance.

A term introduced by the → International Astronomical Union (August 2006) to name the → solar system bodies other than → planets and → dwarf planets. Small solar system bodies include → asteroids, → comets, and → meteoroids.

→ small; → solar; → system; → body.