An Etymological Dictionary of Astronomy and Astrophysics
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Any power obtained by converting solar radiation into useful power.

→ solar; → power.

A space probe designed to gather data about the Sun.

→ solar; → probe.

A large, arch-shaped filament of hot gas extending outward from the Sun's surface. More at → prominence.

→ solar; → prominence.

All the constituents making up the Sun's emission: photons, electrons, protons, neutrinos, and atomic nuclei.

→ solar; → radiation.

The → radiation pressure of solar photons, which pushes a comet's dust outward to form a → dust tail.

→ solar; → radiation; → pressure.

Plural form of → solar radius.

→ solar; → radii.

A unit of length, representing the radius of the → Sun, used to express the size of stars in astrophysics. It is equivalent to: 695,700 km, 0.00465047 → astronomical units, 7.35355 × 10^-8 → light-years, and 2.32061 → light-seconds.

→ solar; → radius.

The motion of the Sun around an axis which is roughly perpendicular to the plane of the → ecliptic; the Sun's rotational axis is tilted by 7.25° from perpendicular to the ecliptic. It rotates in the → counterclockwise direction (when viewed from the north), the same direction that the planets rotate (and orbit around the Sun). The Sun's rotation is differential, i.e. the period varies with latitude on the Sun (→ differential rotation). Equatorial regions rotate in about 25.6 days. The regions at 60 degrees latitude rotate more slowly, in about 30.9 days.

→ solar; → rotation.

A space vehicle designed to orbit about the Sun.

→ solar; → satellite.

The spectrum of the Sun's electromagnetic radiation, consisting of a continuum spectrum marked with dark absorption lines.

→ solar; → spectrum.

The collective name for the Sun and all objects gravitationally bound to it. These objects are the eight planets, their 166 known moons, five dwarf planets, and billions of small bodies. The small bodies include asteroids, icy Kuiper belt objects, comets, meteoroids, and interplanetary dust. The solar system is roughly a sphere with a radius greater than 100,000 AU. Planets, satellites, and all interplanetary material together comprise only about 1/750 of the total mass. Geochemical dating methods show that the solar system chemically isolated itself from the rest of the Galaxy (4.7 ± 0.1) × 10⁹ years ago.

→ solar; → system.

Same as → protosolar abundance.

→ solar system; → abundance.

A telescope designed so that heating effects produced by the Sun do not distort the images.

→ solar; → telescope.

The time based on the rotation of the Earth relative to the Sun. → mean solar time.

→ solar; → time.

A structure used in solar observations in order to raise the equipment above the atmospheric disturbances caused by solar heating of the ground and the radiation of the heat into the atmosphere.

→ solar; → tower.

An ideal star possessing fundamental physical parameters (mass, chemical composition, age, effective temperature, luminosity, gravity, magnetic fields, equatorial rotation, etc.) very similar, if not identical, to those of the Sun. See also → solar analog; → solar-like star.

→ solar; → twins paradox.

The rate of change of the Sun's position with respect to the local standard of rest toward the → solar apex.

→ solar; → velocity.

A mass outflow, consisting of protons, electrons, and other subatomic particles, expelled constantly from the solar corona at about 500 km per second. The solar mass-loss rate in this phenomenon amounts to about 2 x 10^-14 solar masses per year, or about 10⁶ tons per second. → stellar wind.

→ solar; → wind.

The period of time required for the Earth to make one complete revolution around the Sun. Solar year is a general term for: → tropical year, → vernal equinox year, and → autumnal equinox year, which have different lengths.

→ solar; → year.

A member of a very broad class of stars in which is found a mixture of late F, early, middle, and, sometimes, late G type dwarfs and sub-giants. See also → solar analog; → solar twin.

→ solar; → -like; → star.