An Etymological Dictionary of Astronomy and Astrophysics
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The generic name applied to books in Arabic and Persian that tabulate parameters used for astronomical calculations of positions of the Sun, the Moon, and the five planets of antiquity. Some examples: Zij al-Sindhind, by Khwarizmi (c. 780-850), Az-Zij as-Sabi by al-Battâni (Albatenius) (853-929), Zij-i Ilkhâni by Nassireddin Tusi (1201-1274), Zij-i Sultâni by Ulugh Brg (1437), → Toledan Tables, → Alfonsine Tables.

The word is derived from Mid.Pers. zig, variant zih "cord, string" (Mod.Pers. zeh "cord, string"); Av. jiiā- "bow-string," cognate with Skt. jiyā- "bow-string," PIE base *g^whi- "thread, tendon" (from which derive also Gk. bios "bow", L. filum "thread", Russ. žca "thread").
The term zig originally referred to the threads in weaving, but because of the similarity between the rows and columns of astronomical tables and the parallel threads, it came to be used for an astronomical table, and subsequently a set of tables.

A metallic, lustrous, bluish-white → chemical element; symbol Zn. → Atomic number 30; → atomic weight 65.38; → melting point 419.58 °C; → boiling point 907 °C; → specific gravity 7.133 at 25 °C. It was recognized as a → metal as early as 1374.

From the Ger. Zink of unknown origin. Zinc compounds were known in prehistoric times, where they were used for healing wounds and for making brass.

Ruy, from Mid.Pers. rôy, rôd "copper, brass;" Av. raoiδita- "red, reddish;" cf. Skt. rohita- "red, reddish," lohá- "red, reddish, reddish metal."

A common mineral, zirconium silicate, ZrSiO₄, occurring in small tetragonal crystals. The color is variable, usually brown to reddish brown, but also colorless, pale yellowish, green, or blue. A red variety, used as a gem, is called hyacinth. Zircon contains trace amounts of uranium and thorium and therefore can be used for radiometric datings. Also called jargon.

From Ger. Zirkon, from Ar. zarqun "cinnabar, bright red," from Pers. zargun "gold-colored," from zar→ gold + -gun "resembling; manner, fashion; color" (Mid.Pers. gônak "kind, species;" Av. gaona- "color").

A metallic chemical element; symbol Zr. Atomic number 40; atomic weight 91.22; melting point about 1,852°C; boiling point 4,377°C; specific gravity 6.5 at 20°C. Zirconium was discovered in the mineral zirconia by the German chemist Martin-Heinrich Klaproth in 1789. It was first isolated by the Swedish chemist Jons Jacob Berzelius in 1824 in an impure state and finally by the chemists D. Lely Jr. and L. Hamburger in a pure state in 1914.

From → zircon.

A → diatomic molecule made up of → zirconium and → oxygen atoms. See → ZrO band.

→ zirconium; → band.

An imaginary belt around the heavens extending about 9° on either side of the → ecliptic. The orbits of the Moon and of the principal planets also lie entirely within the zodiac. The zodiac was created during the first half of the first millennium B.C. by Babylonian astronomers, who divided it into 12 constellations (→ sign of the zodiac) each considered to occupy 1/12, or 30°, of its great circle. They were named after living creatures, with the exception of Libra: → Aries, → Taurus, → Gemini, → Cancer, → Leo, → Virgo, → Libra, → Scorpius, → Sagittarius, → Capricornus, → Aquarius, → Pisces. However, as a result of → precession, these signs no longer correspond to the astronomical constellations in which the Sun actually appears. The constellations are irregular in size and shape, and the Sun regularly passes through 13 constellations as it moves along the ecliptic. The additional 13th constellation is → Ophiuchus, situated between → Scorpius and → Sagittarius. See also → dodekatemorion.

From M.E. zodiaque, from O.Fr. zodiaque, from L. zodiacus, from Gk. zodiakos (kyklos) "zodiac (circle)," literally "circle of little animals," from zodiaion, diminutive of zoion "animal," literally "a living being," from PIE base *gwei- "to live, life;" cognate with Pers. zist, → bio-.

Borjgân, from borj, → sign of the zodiac, + -gân suffix denoting multiplicity, order, organization.

Of or relating to the → zodiac.

→ zodiac; → -al.

→ zodiac.

→ zodiacal; → belt.

A cone-shaped faint glow along the → ecliptic, visible to the naked eye in the west after sunset or in the east before sunrise. Zodiacal light results from sunlight reflected by interplanetary dust concentrated in the plane of the ecliptic.

→ zodiacal; → light.

→ sign of zodiac.

→ zodiacal; → sign.

The portion of the surface of a sphere included between two parallel planes.

From L. zona "geographical belt, celestial zone," from Gk. zone "a belt," related to zonnynai "to gird," from PIE base *yes- "to gird, girdle;" cognate with Pers. parhun "circle," as below.

Zonâr most probably loan from from Gk., as above; it is related to Pers. parhun "circle," ultimately from Proto-Iranian *pari-iâhana- "girdle, belt," from pari-, variant pirâ-, → circum-, + iâhana- "to girdle," cf. Av. yâh- "to girdle." The Pers. pirâhan "shirt" is a variant of parhun.

The region on the sky covered by the plane of the → Milky Way. It is characterized by an apparent absence of galaxies, due to the obscuring effect of → interstellar dust in the → Galactic plane.

→ zone; → avoidance.

Any of the three → absorption bands due to the molecule → zirconium oxide present in the blue and visual spectral regions → S-type stars. The bands are centered on the wavelengths 4614, 5551, and 6468 Å.

→ zirconium oxide; → band.

A member of a class of non-radially pulsating stas that change their brightnesses with periods from 30 seconds to 25 minutes and amplitudes from 0.001 to 0.2 mag in V. Their location on the → Hertzsprung-Russell diagram identifies them as → white dwarf stars that have entered the → instability strip as they evolve along the white dwarf track.

→ Cetus; → star.

The → fine structure → emission line of → carbon at 157.74 μm, with transition ²P_3/2-²P_1/2 (rest frame frequency 1900.54 GHz). [C II] is a major → cooling line in → molecular clouds and is produced in low density → photodissociation regions (PDRs) (n_H≤ 10³ cm^-3). In higher density PDRs the [O I] 63 μm line becomes an important → coolant. The [C II] line traces → neutral gas exposed to → ultraviolet  → photons from → young stars. The [C II] line is used to probe the stellar → radiation field and find out how it affects the physical conditions of the gas. The bulk of the [C II] emission line is believed to originate from PDRs, and the remainder from → X-ray Dissociation regions (XDRs), and, in a lesser extent, by cosmic-ray-dominated regions (CRDRs), → H II regions, low-density warm gas and/or diffuse H I clouds.

→ carbon; → line.

The two → forbidden lines with → transitions from the upper → energy level  ¹D₂ of the doubly ionized oxygen atom. They occur in the green part of the → visible spectrum and are called → nebular lines. They are λ5006.8 ¹D₂-³P₂ and λ4958.9 ¹D₂-³P₁. Theoretical values for the [O III] 5007/4959 line-intensity ratio is 3.01 (Storey and Zeippen, 2000, MNRAS 312, 813).

[O III], spectroscopic notation of the ion O⁺⁺; → doublet.