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

A technical scale that categorizes the → impact hazard of a → near-Earth object (NEO). It compares the threat of a given NEO to the so-called background threat of all NEOs of the same size or larger. In this way, the probability of the → impact itself as well as the time until the predicted impact are considered. The scale is → logarithmic and continuous. A Palermo scale of -2 indicates that the predicted event is only 1% as likely as a random background event between now and the time of predicted impact. A value of 0 indicates that the risk is the same as the risk from the background threats. A value of +2 indicates an event that is 100 times more likely than the background hazard. The Palermo scale is defined in the paper "Quantifying the risk posed by potential Earth impacts" by Chesley et al. (2002), Icarus 159n 423. See also → Torino scale.

Named after Palermo, in recognition of the Palermo Observatory, where in 1801 the first and largest asteroid (→ Ceres) was discovered by the Italian astronomer Giuseppe Piazzi (1746-1826); → scale.

A silvery white metal which belongs to the → platinum group elements, symbol Pd. → Atomic weight 106.4, → atomic number 46, → melting point 1554.9 °C, → boiling point 2963 °C. It is used in alloys and as a catalyst.

Named 1803 by discoverer William Hyde Wollaston (1766-1828), after the asteroid → Pallas, which was discovered at about the same time.

A class of → iron meteorite containing → olivine crystals.

Named after the German naturalist Peter Pallas (1741-1811), who first studied such a type of meteorites.

An observatory located atop Palomar Mountain about 65 km north-northeast of San Diego, California. It is a center of astronomical research owned and operated by the California Institute of Technology (Caltech). The Observatory is home to three active research telescopes: the 200-inch (5.1-meter) Hale Telescope, the 48-inch (1.25-meter) Samuel Oschin Telescope, and the 60-inch (1.5-meter) telescope. Research at Palomar Observatory is pursued by a broad community of astronomers from Caltech and other domestic and international partner institutions. The famous Hale Telescope proved instrumental in cosmological research. It was the largest instrument of its kind until 1976.

Palomar, a mountain ridge in the Peninsular Ranges in northern San Diego County whose highest elevation is 1,871 m; → Observatory.

A photographic atlas of the northern hemisphere and a portion of the southern hemisphere created at Mount → Palomar Observatory in southern California. The original survey was completed in 1954 using the 48-in Schmidt (Oschin) Telescope. The square photographic plates were 35.5 cm (14-inch) on a side, each encompassing roughly 6 × 6 degrees of the sky. The survey was originally intended to cover the entire sky from +90 degrees declination down to -24 degrees (plate centers) in 879 regions, using both red and blue sensitive emulsions, and including stars to magnitude +22. Ultimately the survey was extended to -30 degrees (both red and blue), an additional 57 regions. Finally, the Whiteoak Southern Extension was added in 1962 (red plates only), with another 100 plates which extended the set down to a declination of -42 degrees plate center.

→ Palomar Observatory; → sky; → survey.

The innermost of Saturn's known satellites, orbiting within the Encke Division in the A Ring at a distance of 133,583 km. Also know as Saturn XVIII. It orbits Saturn every 0.575 days and its diameter is about 20 km. Pan was discovered in 1990 from Voyager photos taken in 1981.

In Gk. mythology, Pan was the god of woods, fields, and flocks, having a human torso and head with a goat's legs, horns, and ears.

A prefix meaning "all, whole," used as a general formative (panorama; pantelegraph; pantheism; pantonality), and especially in terms implying the union of all branches of a group (Pan-Christian; Pan-Hellenic; Pan-Slavism).

From Gk. pan-, combining form of pas (neuter pan) "all, every," of unknown origin.

Pân- loan from Gk., as above.
Sarâsar- "all, entirely, the whole," literally "from beginning to end; from one end to the other," from sar "head" + -â- epenthetic vowel + sar. The main word sar is related to soru, sorun "horn" (karnâ "a trumpet-like wind instrument," variant sornâ "a wind instrument"); Mid.Pers. sar "head," sru "horn;" Av. sarah- "head," srū- "horn, nail;" cf. Skt. śiras- "head, chief;" Gk. kara "head," karena "head, top," keras "horn;" L. cornu "horn," cerebrum "brain;" P.Gmc. *khurnaz (Ger. Horn, Du. horen; cognate with E. horn, as above, from PIE *ker- "head, horn;" O.E. horn "horn of an animal," also "wind instrument;" E. horn); PIE base *ker- "head, horn, top, summit."
Hamé-, → all.

A system for wide-field astronomical imaging developed and operated by the Institute for Astronomy at the University of Hawaii. Its goal is to survey the sky for moving or variable objects on a continual basis, and also produce accurate astrometry and photometry of already detected objects. It is situated at Haleakala Observatories near the summit of Haleakala in Hawaii. Pan-STARRS1 (PS1) was the first part of Pan-STARRS. The survey used a 1.8 meter telescope and a 1.4 Gigapixel camera to image the sky in five broadband filters (g, r, i, z, y). The PS1 consortium is made up of astronomers and engineers from 14 institutions and six countries. The survey was completed in April 2014. The Pan-STARRS Project is now focusing on building PS2.

Short for Panoramic Survey Telescope and Rapid Response System.

A thin, flat cake of batter fried on both sides on a griddle or in a frying pan (Dictionary.com).

From M.E., from pan "a usually broad, shallow, and open container for domestic use, as for cooking;" O.E. panne + cake, from M.E., from O.N. kaka "cake," cognate with M.E. kechel "little cake;" G. Kuchen;

Lavâš "a sort of thin flattened bread."

A model of galaxy formation in which regions of primordial gas as massive as clusters of galaxies began to collapse into thin sheets (pancakes). Within the pancakes, smaller regions of gas later collapsed to form individual galaxies.

→ pancake; → model.

A star strongly compressed due to the → tidal force of a → massive black hole. The intense → gravity of the → black hole pulls harder on the nearest part of the star, creating an imbalance. When the star penetrates the → tidal radius, first it becomes cigar-shaped, then the squeezing of the tidal forces flattens the star in its orbital plane to the shape of a → pancake. Next the star rebounds, and as it leaves the tidal radius, it starts to expand. A little further on its orbit the star finally breaks up into gas fragments. This flattening would increase the → density and → temperature inside the star enough to trigger intense nuclear reactions that would tear it apart (Brassart & J.-P. Luminet, 2008, Astron. Astrophys. 481, 259).

→ pancake; → star.

One of the inner moons of Saturn and the outer shepherd moon for the F-ring. It was discovered in 1980 from Voyager 1 photos and is also known as Saturn XVII.

In Gk. mythology Pandora was the very first woman who was formed out of clay by the gods. She was bestowed upon humankind by Zeus as a punishment for Prometheus' theft of fire. Entrusted with a box containing all the ills that could plague people, she opened it out of curiosity and thereby released all the evils of human life.

1) One of the divisions of a window or the like, consisting of a single plate of glass in a frame. A plate of glass for such a division.
2) A panel, as of a wainscot, ceiling, door, etc (Dictionary.com).

M.E. pane, pan "strip of cloth, section," from M.Fr. pan, from O.Fr. pan "section, piece, panel," from L. pannum "piece of cloth, garment;" cf. Goth. fana "piece of cloth," Gk. penos "web," O.E. fanna "flag."

Poš, from Baluci poc "cloth, clothing," from puš-, pušidan "to cover, to wear," → envelope.

1) A distinct portion, section, or division of a wall, wainscot, ceiling, door, shutter, fence, etc., especially of any surface sunk below or raised above the general level or enclosed by a frame or border.
2) A comparatively thin, flat piece of wood or the like, as a large piece of plywood.
3) A group of persons gathered to conduct a public discussion, judge a contest, serve as advisers, be players on a radio or television game, or the like (Dictionary.com).

M.E., from O.Fr. panel "a piece (of anything)," diminutive of pan "piece of cloth or the like," ultimately from L. pannus "piece of cloth." The sense of "a small group of people called on to discuss, judge, advice on a particular matter" is from 1570s.

Pošel, from poš, → pane, + -el, → -al.

Hypothetical super-continent that existed from about 300 to 200 million years ago. It has since broken up and the fragments have drifted to become the configuration of Earth's present-day continents.

From Gk. → pan- "all" + gaia, variant ge "earth, land, ground, soil."

Pânzam, from → pan- + zam, variants zamin, zami "earth, ground," from Mid.Pers. zamig "earth;" Av. zam- "the earth;" cf. Skt. ksam; Gk. khthôn, khamai "on the ground;" L. homo "earthly being" and humus "the earth" (as in homo sapiens or homicide, humble, humus, exhume); PIE root *dh(e)ghom "earth."
Pânžé, loan from Fr.

The hypothesis that life exists and is distributed throughout the Universe in the form of "seeds" that develop in the right environment. The oldest record of this idea may be traced back to the ancient Greek philospher Anaxagoras, who lived in the fifth century B.C.

N.L., from Gk. panspermia "mixture of all seeds," from → pan- + -sperm, a combining form of sperma "seed" + -ia a noun suffix.

Pân-dâne-vari, sarâsar-dâne-vari, from pân-, sarâsar-, → pan-, + dâné "seed, grain" (Mid.Pers. dân, dânag "seed, corn," Av. dânô- in dânô.karš- "carrying grains; an ant," Skt. dhânâ- "corn, grain," Tokharian B tâno "grain," cf. Lith. duona "corn, bread") + -var suffix of possession, variant -ur (Mid.Pers. -uwar, -war; from O.Pers. -bara, from bar- "to bear, carry") + -i noun suffix.

1) The doctrine that God is the transcendent reality of which the material universe and human beings are only manifestations: it involves a denial of God's personality and expresses a tendency to identify God and nature.
2) Any religious belief or philosophical doctrine that identifies God with the universe (Dictionary.com).

→ pan-; → theism.

1) A thin sheet made from fibrous material (wood pulp, rags, straw, etc.) suitable for writing or printing on.
2) A written or printed document or the like.

From M.E. papire, from L. papyrus "paper," from Gk. papyros "any plant of the paper plant genus," may be of Egyptian origin.

Kâqaz "paper," probably a transliteration of old Chinese gu zhi; cf. Sogd. kāγaδā "paper," Skt. kakali, kakari, Marathi kagad, Tamil kagidam, Malayalam kayitam (Y. Kumar, 2005, A History of Sino-Indian Relations).

The → water molecule in which the → nuclear spins of the constituent → hydrogen atoms are → antiparallel (→ parahydrogen). See also: → ortho-water.

→ para-; → water.

A plain curve obtained by slicing a cone with a plane parallel to one side of the cone. A parabola can be considered an ellipse with an infinite major axis. It is one of the types of conic sections.

N.L., from Gk. parabole "comparison, application," literally "a throwing beside," from → para- + bole "throwing," related to ballein "to throw."

Sahmi, of unknown origin.