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

A crater about 200 km in diameter on the northern coast of the Yucatan Peninsula, near the town of Chicxulub, Mexico. It is attributed to a 10 km wide → asteroid that hit the Earth about 65 million years ago (→ Chicxulub impactor). Ten years before the 1990 discovery of the Chicxulub crater, physicist Luis Alvarez and geologist Walter Alvarez proposed a theory to explain the formation of the crater. They noted increased concentrations of the element → iridium in 65-million-year-old clay. Iridium is rare on Earth, but it's more common in some objects from space, like → meteors and asteroids. According to the Alvarez theory, a massive asteroid had hit the Earth, blanketing the world in iridium. The collision caused fires, climate change and widespread extinctions, among which that of dinosaurs, who had lived for 180 million years.

Named after a twon in the Mexican state of Yucatan, which lies near the geographic center of the → crater.

An object having an estimated mass between 1.0 × 10¹⁵ and 4.6 × 10¹⁷ kg, which struck the Earth at the → Cretaceous-Tertiary event about 65 million years ago. It was probably an → asteroid 10 km in diameter with a velocity of roughly 20 km per sec at an angle of just under 60°. The collision created the → Chicxulub crater. The event was responsible for eliminating approximately 70 percent of all species of animals at or very close to the boundary between the Cretaceous and Paleogene periods.

→ Chicxulub crater; → impactor.

1) A person between birth and puberty; a son or daughter; an offspring.
2) In → graph theory, the → vertex (node) below a given vertex connected by its → edge downward. In other words, in a rooted tree, a vertex v is a child of vertex w if v immediately succeeds w on the path from the root to v. Vertex v is a child of w if and only if w is the parent of v.

M.E.; O.E. cild "fetus, infant;" akin to Goth. kilthai "womb."

Farzand, from Mid.Pers. frazand "child;" Av. frazanti- "progeny, offspring," from fra- "forward, along," → pro-, + zan "to give birth;" → birth.

A → lunisolar calendar (Chinese: yīnyáng li), which is now mainly used for determining cultural festivals. It is based on astronomical observations of the Sun's annual apparent motion (→ ecliptic) and → lunar phases. The calendar starts at Chinese New Year and consists of 12 or 13 → lunar months. The ecliptic is divided into 24 sections (jiéqi) of 15° each. In general, Chinese New Year falls on the day of the second new Moon after the → winter solstice on approximately December 22. Since 12 months are about 11 days shorter than the → tropical year, a → leap month is inserted to keep the calendar in tune with the seasons. An ordinary → lunar year has 353-355 days while a → leap year has 383-385 days. Therefore, the → solstices and → equinoxes move 11 (or 10 or 12) days later. Each 13-month leap year is about 19 days too long, so the solstices and equinoxes jump 19 (or 18 or 20) days earlier. Each year is assigned a name consisting of two components within a 60-year cycle. The first component is a celestial stem. The second component is a terrestrial branch; it features the names of animals in a zodiac cycle consisting of 12 animals. Each of the two components is used sequentially. Therefore, the first year of the 60-year cycle becomes jia-zi, the second year is yi-chou, and so on. One starts from the beginning when the end of a component is reached. The 60th year is gui-hai. The current 60-year cycle started on 2 February 1984. The leap year must be inserted if there are 13 new moons from the start of the 11th month in the first year to the start of the 11th month in the second year. The beginnings of the Chinese calendar can be traced back to the 14th century BC. Legend has it that the Emperor Huang-di invented the calendar in 2637 BC. The calendar has been adopted by several southeast Asian cultures. The Chinese calendar has undergone several reforms, the last one in 1645. For more details, see, e.g., Helmer Aslaksen, The Mathematics of the Chinese calendar, e-paper.

Chinese adj. of China, from Pers. Cin [Chin], from Qin the first imperial dynasty of China (221 to 206 BC); → calendar.

The quality of an object that is not superimposable on its mirror image.

From Gk. cheir "hand;" from PIE *ghes- "hand."

Xirâl, loan from Gk., as above.

The geometric property of a rigid object that is → chiral.

→ chiral; → -ity.

An object, discovered in 1977, which was initially assumed to be an asteroid, but subsequent observations showed it to be a weak comet with a detectable coma. Its orbit, lying now between those of Saturn and Uranus, is unstable on time scales of a million years.

In Gk. mythology, Xειρων (Cheiron or Chiron) was the wisest of the Centaurs; he was not a drunkard like other Centaurs. Chiron was tutor to Jason and Heracles. He was the only immortal centaur.

1) Telecommunications: A signal in which the wave frequency increases or decreases, linearly or exponentially, with time.
2) Astro: The theoretically predicted → gravitational wave arising from the interaction of two highly → compact objects. As the two objects spiral toward each other, due to orbital energy loss, the frequency and amplitude of the gravitational wave will increase continuously.

Chirp "a short, high-pitched sound, such as that made by certain birds or insects," from M.E. chirpen, of onomatopoeic origin.

Cirp loanword from E., as above.

A pattern formed by fine powder or salt placed on a vibrating surface. The figures display the positions of → nodes and → antinodes.

Named after Ernst Chladni (1756-1827), German physicist; → figure.

1) A negative ion, ClO₃^- derived from chloric acid.
2) Any salt of chloric acid.

From chlor-, → chlorine, + → -ate.

A colorless, strong acid HClO₃, formed by the action of dilute sulfuric acid on barium chlorate.

From chlor-, → chlorine, + → -ic; → acid.

A gaseous → chemical element of the halogen group, which is greenish yellow and poisonous; symbol Cl. → Atomic number 17; → atomic weight 35.453; → melting point -100.98°C; → boiling point -34.6°C. Chlorine is about two and one-half times as dense as air. It is used for water purification, in the making of bleaching powder. Its compounds occur as common → salt (sodium chloride), NaCl, in sea water and as rock salt. Chlorine is the first poison gas to be used in warfare (by German army, the Second Battle of Ypres, 1915). It has several → radioactive isotopes, in particular ³⁶Cl with a half-life of 3 × 10⁵ years. Chlorine was discovered by the Swedish pharmacist and chemist Carl-Wilhelm Scheele (1742-1786) in 1774. In 1810, the English chemist Humphry Davy (1778-1829) proved it was an element and gave it the name chlorine.

From Gk. chloros "light green, greenish yellow;" cognate with Pers. zard "yellow," zarr "gold;" E. → gold, → yellow.

The most common type of → meteorites containing → chondrules. These → stony meteorites make up about 86% of all meteorites. An important feature of the chondrites is that, with the exception of a few highly → volatile elements, they have the same composition as the Sun.

Chondrite, from chondr-, from chondros "grain", + suffix → -ite.

Millimeter-sized grains of → silicate sometimes found in large numbers in → chondrite meteorites. They are essentially glassy beads made by a violent but brief heating event that caused dust grains to form melt droplets. However, the cause of the heating remains unknown.

From Gk. chondr-, from chondros "grain," + diminutive suffix → -ule.

A member of the → crow family with a red beak and legs.

M.E. choghe; akin to O.E. ceo, Du. kauw, Dan. kaa.

Kalajik, from Daštak Baxtiyâri dialect, related to kal, kalâq, → crow.

A abbreviated notation for various functions associated with quadratic differential forms. Each Christoffel symbol is essentially a triplet of three indices, i, j and k, where each index can assume values from 1 to 2 for the case of two variables, or from 1 to n in the case of a quadratic form in n variables. Christoffel symbols appear in many calculations in geometry where non-Cartesian coordinates are used. These symbols are fundamental in the study of tensor analysis.

Named after Elwin Bruno Christoffel (1829-1900), a German mathematician; → symbol.

Of or relating to color or color phenomena or sensations.

From L. chromaticus, from Gk. khromatikos "relating to color," from khroma, khromat- "color" + → -ic.

From rang, fâm, → chromo-, + -i adj. suffix.

A defect in a lens that causes it to concentrate the various colors in a beam of light at various point, thus producing color fringes.

→ chromatic; → aberration.

A silver-gray, lustrous, brittle, hard metallic → chemical element that is resistant to tarnish and corrosion; symbol Cr. → Atomic number 24; → atomic weight 51.996; → melting point about 1,857°C; → boiling point about 2,672°C; → specific gravity about 7.2 at 20°C. Chromium is used in the hardening of steel alloys and the production of stainless steels. It is extracted by reducing the oxide with → aluminium. Its → radioactive isotope ⁵¹Cr has a half-life of 27.8 days. It was discovered in 1797 by the French chemist and pharmacist Nicolas-Louis Vauquelin (1763-1829).

From the Gk. chroma "color," from the many colored compounds of this element, + -ium a suffix used in the name of several chemical elements.

A prefix indicating "color, colored." Before a vowel: chrom-.

Combining form from Gk. chroma, khroma "color."

Rang, → color; fâm "color," probably related to bâm "light; morning light; splendor" (bâmdâd "morning,; splendor, light"); Mid.Pers. bâm "brillance, glory, splendor," bâmig "brilliant, glorious;" Av. bā- "to shine, appear, seem," (with ā-) auuā- "to have the appearance of, be like," (with fra-) frauuā- "to shine," (with ni-) -niuuā- "to radiate downward," (with ui-) viuuā- "to shine forth;" cf. Gk. phaos, phos "light," phainein "to show, to bring to light;" Skt. bhā- "to shine," bhati "shines, glitters," O.Ir. ban "white, light, ray of light."