An Etymological Dictionary of Astronomy and Astrophysics

The puzzle of why the night sky is not as uniformly bright as the surface of the Sun if, as used to be assumed, the Universe is infinitely large and filled uniformly with stars. It can be traced as far back as Johannes Kepler (1571-1630), was discussed by Edmond Halley (1656-1742) and Philippe Loys de Chéseaux (1718-1751), but was not popularized as a paradox until Heinrich Olbers took up the issue in the nineteenth century. This paradox has been resolved by the → Big Bang theory. In a Universe with a beginning, we can receive light only from that part of the Universe close enough so that light has had time to travel from there to here since the Big Bang. The night sky is dark because the galaxies are only about ten billion years old and have emitted only a limited amount of light, not because that light has been weakened by the expansion of the Universe (P. S. Wesson et al., 1987, ApJ 317, 601).

See also: Formulated in 1826 by Heinrich Wilhelm Olbers (1758-1840),
German physician and amateur astronomer, who discovered the asteroids Pallas and Vesta as well as five comets; → paradox.

The puzzle of why the night sky is not as uniformly bright as the surface of the Sun if, as used to be assumed, the Universe is infinitely large and filled uniformly with stars. It can be traced as far back as Johannes Kepler (1571-1630), was discussed by Edmond Halley (1656-1742) and Philippe Loys de Chéseaux (1718-1751), but was not popularized as a paradox until Heinrich Olbers took up the issue in the nineteenth century. This paradox has been resolved by the → Big Bang theory. In a Universe with a beginning, we can receive light only from that part of the Universe close enough so that light has had time to travel from there to here since the Big Bang. The night sky is dark because the galaxies are only about ten billion years old and have emitted only a limited amount of light, not because that light has been weakened by the expansion of the Universe (P. S. Wesson et al., 1987, ApJ 317, 601).

See also: Formulated in 1826 by Heinrich Wilhelm Olbers (1758-1840),
German physician and amateur astronomer, who discovered the asteroids Pallas and Vesta as well as five comets; → paradox.

Of an astronomical object, having existed as specified with relation to younger or newer objects of the same category; e.g. → old star.

Etymology (EN): From M.E., from O.E. eald, ald; cf. Du. old, Ger. alt, Goth. altheis; akin to O.N. ala “to nourish.”

Etymology (PE): Kohan “old, ancient,” kohné “worn;” Mid.Pers. kahwan “old, aged, worn.”
Pir, from Mid.Pers. pir “old, aged, ancient;” Av. parô (adv.) “before, before (of time), in front (of space);” cf. Skt. puáh, combining form of puras “before (of time and place), in front, in advance.”

Of an astronomical object, having existed as specified with relation to younger or newer objects of the same category; e.g. → old star.

Etymology (EN): From M.E., from O.E. eald, ald; cf. Du. old, Ger. alt, Goth. altheis; akin to O.N. ala “to nourish.”

Etymology (PE): Kohan “old, ancient,” kohné “worn;” Mid.Pers. kahwan “old, aged, worn.”
Pir, from Mid.Pers. pir “old, aged, ancient;” Av. parô (adv.) “before, before (of time), in front (of space);” cf. Skt. puáh, combining form of puras “before (of time and place), in front, in advance.”

A member of a population of stars that, according to stellar evolution theories,
are almost as aged as the galaxy in which it resides.

See also: → old; → star.

A member of a population of stars that, according to stellar evolution theories,
are almost as aged as the galaxy in which it resides.

See also: → old; → star.

A population of stars in a stellar system that have definitely left the → main sequence.

See also: → old; → stellar; → population.

A population of stars in a stellar system that have definitely left the → main sequence.

See also: → old; → stellar; → population.

A silicate mineral of magnesium (Mg₂SiO₄) and iron (Fe₂SiO₄,) found commonly in basalt and in carbonaceous chondrites.

See also: From Ger. Olivin, from olive, because of its olive-green to gray-green color,

• -in equivalent to -ine a noun suffix used in chemical and mineralogical nomenclature.

A silicate mineral of magnesium (Mg₂SiO₄) and iron (Fe₂SiO₄,) found commonly in basalt and in carbonaceous chondrites.

See also: From Ger. Olivin, from olive, because of its olive-green to gray-green color,

• -in equivalent to -ine a noun suffix used in chemical and mineralogical nomenclature.

The highest peak on Mars, and the largest volcano in the solar system. It rises to a height of 27 kilometres above the datum level selected on the basis of atmospheric pressure.This gigantic shield volcano, 700 kilometres across, is similar in nature to volcanoes on Earth but its volume is at least fifty times greater than its nearest terrestrial equivalent.

See also: From L. Mons, → mountain, + Olympus, from Gk. Olympos a mountain (2966 m) in north-east Greece, on the boundary between Thessaly and Macedonia, mythical abode of the greater Grecian gods.

The highest peak on Mars, and the largest volcano in the solar system. It rises to a height of 27 kilometres above the datum level selected on the basis of atmospheric pressure.This gigantic shield volcano, 700 kilometres across, is similar in nature to volcanoes on Earth but its volume is at least fifty times greater than its nearest terrestrial equivalent.

See also: From L. Mons, → mountain, + Olympus, from Gk. Olympos a mountain (2966 m) in north-east Greece, on the boundary between Thessaly and Macedonia, mythical abode of the greater Grecian gods.