An Etymological Dictionary of Astronomy and Astrophysics
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The analytical solution to the → hydrodynamic equations describing the → collapse of an → isothermal sphere. The Larson-Penston solution is → self-similar for a purely dynamical isothermal collapse with spherical symmetry. It corresponds to the collapse prior to the formation of a → protostar, and thus is suitable for the study of → pre-stellar cores. The Larson-Penston solution was extended by Shu (1977) to obtain a whole family of solutions for this problem.

Named after R. B. Larson (1969, MNRAS 145, 271) and M. V. Penston (1969, MNRAS 144, 425), who simultaneously, but independently, did this study.

The quality of an instrument that lacks sufficient resolution for a specific observation. This is a relative quality, but presently a resolution below about 1 arcsecond.

→ low; → resolution.

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.

The state, process, or condition of being or becoming obsolete or outdated and no longer used.

→ obsolete; → -escence.

Becoming obsolete; passing out of use.

→ obsolete; → -escent.

1a) No longer in general use; fallen into disuse.
1b) Biology: (of a living organism) Reduced to a redument, or completely lacking, as compared with a corresponding part in related organisms.
2) To make obsolete by replacing with something newer or better.

From L. obsoletus "grown old, worn-out," p.p. of obsolescere "fall into disuse, be forgotten about, become tarnished," which probably is from ob "away" + an expanded form of solere "to be used to, be accustomed."

Pitâr, from Tabari pitâr "worn out," specifically "rotten tree," pitə-pât "anything worn out or useless," from pit, variant of Pers. pud "worn out, decayed," pusidan/pus- "to rot," cf. Pashto puda, Wakhi pitk "rotten, foul," Kurd. (Kurm.) puc "rotten, useless;" Av. pu- "to stink, rot," akin to Gk. puos, L. pus "pus."

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 partial differential equations, the solution which can be obtained from the general solution by particular choice of the arbitrary functions. → general solution; → singular solution.

→ particular; → solution.

The business strategy of deliberately designing products so they have a limited effective lifespan. Its objective is to incite the consumer to abandon the currently owned item and buy another one.

Planned, p.p. of "to → plan;" → obsolescence.

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.

1) The degree to which an → optical system renders visible separate parts of an object. Also known as → angular resolution and → spatial resolution. See also → spectral resolution.
2) The time interval between successive discernible signals. → temporal resolution.

Verbal noun of → resolve.

Finding the → components of a → force which act in specified → directions.

→ resolution; → force.

To separate and make visible the individual parts of an → image or → spectral feature.

M.E. resolven, from L. resolvere "to loosen, undo, settle," from → re- + solvere "to loosen," → solve.

Vâgošudan, from prefix vâ-, → re-, + gošudan, gošâdan "to loose, open up, let free;" gošâd "opened; ample, broad;" Mid.Pers. wišâdan "to let free;" Khotanese hīyā "bound;" O.Pers. višta "untied, loosened," vištāspa- "with loosened horses" (personal name); Av. višta "untied," ā-hišāiiā "holds fettered," hita- "fastened, tied on, put to;" cf. Skt. sā- "to bind, fasten, fetter," sitá- "bound," ví-sita- "untied."