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

1) A large, solid-hoofed, herbivorous quadruped, Equus caballus, domesticated since prehistoric times.
2) In a → planispheric astrolabe, the small prominence that, inserted into a slit in the pin, prevents the parts of the instrument from coming loose when in use. The part owes its name to the fact that astrolabe-makers would often shape it into a horse's head (online museo galileo, VirtualMuseum).
See also: → horse latitude, → Horsehead Nebula, → horsepower, → horseshoe mounting, → horseshoe orbit.

Horse, O.E. hors, from P.Gmc. *khursa- (cf. M.Du. ors, Du. ros, O.H.G. hros, Ger. Roß "horse"), of unknown origin; → latitude.

Asb "horse," from Mid.Pers. asp; O.Pers. asa- "horse;" Av. aspa- "horse," aspā- "mare," aspaiia- "pertaining to the horse;" cf. Skt. áśva- "horse, steed;" Gk. hippos; L. equus; O.Ir. ech; Goth. aihwa-; O.E. eoh "horse;" PIE base *ekwo- "horse."

The belts of latitude over the oceans, located around 30° north and south of the equator, characterized by predominantly calm or light winds and hot and dry weather.

→ horse; → latitude.
The origin of the term horse latitudes is not clear, despite numerous speculations. A likely explanation appears in Spanish in a natural history text (Historia General y Natural de las Indias by Lopez de Gomara) published in 1535. Therefore, the term derives from El Golfo de las Yeguas, which translates to "The Mares' Sea." The sailors called it this because in the 1500's there was active shipping of horses, particularly brood mares, from Spain to the Canary Islands, and many of the horses died during the transit of this area.

A huge → dark cloud of → interstellar dust that is shaped like a horse's head. It is luminous at its edges because it is in front of the bright → emission nebula IC 434. Its height and width are about 5 and 2.5 → light-years respectively. It is located at a distance of about 1500 light-years in the constellation → Orion. Also known as Barnard 33.

→ horse; → head; → nebula.

A unit that is used to measure the → power of engines and motors.
1) Metric horsepower is equal to the power required to carry a load of 75 kg over a distance of one meter in one second. It is equivalent to 746 → watts.
2) British (US) horsepower is the rate of work when 33,000 foot-pounds of work are done per minute. The horsepower was defined by James Watt (1736-1819), the inventor of the steam engine, to compare the output of steam engines with the power of draft horses. He determined that a horse is typically capable of a power of 550 foot-pounds per second.

→ horse; → power.

Asb-e boxâr "vapor horse," translation of Fr. cheval-vapeur, from asb, → horse, + boxâr, → vapor.

An equatorial mounting in which the upper end of the polar axis frame is made into a horseshoe shape to accommodate the telescope tube.

Horseshoe, from → horse + shoe, from O.E. scoh "shoe," from P.Gmc. *skokhaz (cf. Dan., Swed. sko, O.S. skoh, Du. schoen, O.H.G. scuoh, Ger. Schuh); → mounting.

Barnešând, → mounting; na'l "horseshoe, shoe," loanword from Ar.

A periodic orbit which passes around the → Lagrangian points L4, L3, and L5, but neither of the two primaries. This orbit is shaped like a horseshoe when viewed in a reference frame rotating with the primaries. Such orbits occur in the solar system, for example in the case of the satellites → Janus and → Epimetheus, which share the same orbit around → Saturn. The smaller Epimetheus encompasses both the L4 and L5 points associated with the larger Janus and performs a horseshoe orbit relative to Saturn and Janus. The satellites experience a close approach every 4 years during which their orbits are exchanged. → tadpole orbit.

→ horseshoe mounting; → orbit.