An Etymological Dictionary of Astronomy and Astrophysics

The most luminous and the most extensively studied of → Luminous Blue Variables. Known also as HD 93308, it lies in the → Trumpler 16→ star cluster of the → Carina Nebula and is about 7,500 to 8,000 → light-years away. η Carina probably began its life as a → very massive star with an initial mass of about 150 → solar masses, and has a current estimated mass of about 90-100 solar masses. The difference has been lost in sudden giant eruptions in the past few thousand years. The so-called → Homunculus Nebula results from the mass ejection by η Carinae during its giant outburst around 1843 when it reached a magnitude of -1 and became the second brightest star in the southern sky. About 1880 it reached magnitude 7 and has remained at this level, although with fluctuations.
The 1843 event ejected at least 12 solar masses of gas moving at speeds of up to 650 km s^-1 with a kinetic energy of almost 10⁵⁰ erg. The double-lobed remnant has a mass of about 2.5 solar masses. It is divided by a → torus of cold dust (110 K), about 5 → light-years in radius and 15 solar masses, which was ejected in an earlier event some 1000 years ago. There is strong evidence that η Carinae is a → binary system
with a period of about 5.5 years and a projected separation less than 30 → astronomical units (about 0.013 arcsec). A colliding-wind binary is suggested by the → hard X-ray spectrum. The main component has an estimated → mass loss rate of 10^-3 solar masses per year.

See also: Eta (η), Gk. letter of alphabet; the → Carina constellation.

1. To cut, bite, or corrode with an acid or the like; engrave with an acid or the like, as to form a design in furrows that when charged with ink will give an impression on paper.
   

2. To produce (a design, image, etc.) by this method, as on copper or glass (Dictionary.com).
   

3. Astro.: To cut or corrode an → iron meteorite with a strong → acid to reveal its hidden → crystalline structure.

Etymology (EN): From Du. etsen, from Ger. ätzen “to etch,” from O.H.G. azzon “to cause to bite, feed,” ultimately from PIE root *ed- “to eat;” cf. Av. ad- “to eat;” Mod.Pers. âš “thick brew, soup” (from O.Pers. *āšyā-,
Proto-Ir. *HasH- “to eat”); Skt. ad- “to eat;” Gk. edo “I eat;” Lith. edu “I eat;” O.Irish ithim “I eat;” O.E. etan, O.H.G. essan, Ger. essen “to eat.”

Etymology (PE): Bâ tizâb kandan, literally “to dig with acid,” from bâ “with,” tizâb “acid,” kandan “to dig;” ecidan, from E. etch, cognate with Pers. âš, as above.

1. The act or process of making designs or pictures on a metal plate, glass, etc., by the corrosive action of an acid instead of by a burin.
   

2. An impression, as on paper, taken from an etched plate.
   

3. The design so produced (Dictionary.com).
   

4. The act or process of cutting a smooth cross section of a → meteorite with → acid to reveal its → crystal structure.

See also: Verbal noun of → etch.

A colorless, odorless → hydrocarbon, C₂H₆, which occurs with → methane in natural gas.

See also: From eth-, from → ethyl, + -ane a suffix used in names of hydrocarbons of the methane or paraffin series.

An → alcohol having molecular formula C₂H₅OH. It is a colorless inflammable liquid with a characteristic odor. Ethanol is produced by fermentation of sugar: C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂. It is the active constituent of alcoholic beverages. It is used as a fuel and as a solvent in the extraction of specific substances. It is also known as → ethyl alcohol. Ethanol in the → interstellar medium was first detected
toward the → Sagittarius B2 molecular cloud at
82.265, 90.118, and 104.809 GHz (B. Zuckerman et al. 1975, ApJ 196, L99).

See also: Short for → ethyl alcohol.

1. Physics: A hypothetical medium filling all space formerly postulated to account for the propagation of → electromagnetic radiation through space. In order to facilitate description and to provide a physical explanation of various phenomena involving action at a distance and electromagnetism, a medium had been postulated with mechanical properties adjusted to provide a consistent theory. In 1887 Michelson and Morley attempted to measure the motion of the Earth through the ether. No such motion was detected. The → Michelson-Morley experiment has been repeated under different conditions, but the hypothesis of a stationary ether through which the Earth moves is not verified.
   

2. The substance supposed by Aristotle to constitute stars and fill the outer space.
   

3. Chemistry: A family of organic compounds with the general formula R-O-R’, where R and R’ are hydrocarbon radicals. In particular diethyl ether, C₂H₅OC₂H₅, which is a volatile colorless liquid with a pleasant smell.

See also: From L. æther “the upper air, pure air,” from Gk. aither “upper air,” from aithein “to burn, shine.”

A hypothesis put forward to explain the null measurement of the → ether drift. According to this hypothesis, the Earth somehow drags the ether with it as our planet rotates on its axis and revolves around the Sun. However, the ether drag hypothesis contradicts results from several
experiments, including the → aberration of starlight.

See also: → ether; → drag.

1. The hypothetical motion of the supposed → ether relative to the Earth. The → Michelson-Morley experiment found no ether drift. An analogy is given by a boat drifting in a fast-flowing river due to the river’s current. With the same power, the speed would be slower
   when sailing across the stream. Moreover, in order to reach directly opposite the starting point, the boat would have to be headed somewhat upstream. See also the → ether drag.
   

2. The motion of the Earth relative to the → rest frame defined by the → cosmic microwave background radiation.

See also: → ether; → drift.

A combining form meaning “race, culture, people.”

Etymology (EN): From Gk. ethnos “people, nation, class, tribe.”

Etymology (PE): Qowm- loan from Ar. qaum “people, tribe, family.”

The study of the beliefs, interpretations, and practices of specific cultures regarding celestial objects or phenomena. Ethnoastronomy uses the tools and methodologies of → ethnology in the study of astronomical conceptions.

See also: → ethno-; → astronomy.

The study of specific cultures (ethnic groups) in their different aspects
(anthropological, social, cultural, etc.) to establish similarities and disparities between them.

See also: → ethno-; → logy.

A chemical group, C₂H₅, produced by removing a hydrogen atom from → ethane. For example, ethyl chloride is C₂H₅Cl

See also: From Ger. Ethyl, from eth-, from → ether,

• -yl a suffixed used in the names of radicals.

Same as → ethanol.

See also: → ethyl; → alcohol.

The study of the origins and history of the form and meaning of → words.

Etymology (EN): M.E., from L. etymologia, from
Gk. etymologia, from etymon “true sense” (neuter of etymos) + logos, → -logy.

Etymology (PE): Riše-šenâsi, from rišé “root” (dialectal Tabari rexa; Kurd. regez, riše), from Mid.Pers. rêšak “root,” maybe ultimately related to PIE *u(e)rad-, although the Skt. offshoot is absent (Gk. rhiza “root;” L. radix, radius “staff;” O.H.G. wurz “plant, herb;” Ger. Wurz; O.E. rot; E. root) + -šenâsi, → -logy.