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

The curve traced by a point on the circumference of a circle that rolls along a straight line. The cycloid has a → cusp at every point where it touches the straight line. The distance between cusps is 2πR, where R is the radius of the circle.

Cycloid, from Gk. kykloeides "circular," fr. kyklos "circle," → cycle + eides "form," → -oid.

Carxzâd, from carx "wheel, circle," → cycle + zâd "produced, created, born," from zâdan "give birth" (Av. zan- "to bear, give birth to a child, be born," infinitive zazâite, zâta- "born," cf. Skt. janati "begets, bears," Gk. gignesthai "to become, happen" L. gignere "to beget," gnasci "to be born," PIE base *gen- "to give birth, beget").

Any circulatory wind system in the atmosphere in which the motion is anticlockwise in the northern hemisphere (that is in the same sense as that of Earth) and clockwise in the southern hemisphere, around a center of low pressure.

From Gk. kyklon "moving in a circle, whirling around," pr.p. of kykloun "move in a circle, whirl," from kyklos "circle," cognate with Pers. carx→ cycle.

Carxand "moving in a circle," from carxidan→ rotate, from carx, → cycle.

Having a sense of rotation about the local vertical the same as that of the Earth's rotation. More specifically, as viewed from above, → counterclockwise in the Northern Hemisphere, → clockwise in the Southern Hemisphere, and undefined at the equator. The opposite of → anticyclonic (Meteorology Glossary, American Meteorological Society).

→ cyclone; → -ic.

An → accelerator in which charged subatomic particles generated at a central source are accelerated to acquire energies up to several tens of millions of → electron-volts. The cyclotron consists of two flat, semicircular metal boxes or electrodes, called dees or D's because of their shape. An alternating electric field between the dees continuously accelerates the particles from one dee to the other, while the magnetic field bends their direction guiding them in a circular path. As the speed of the particles increases, so does the radius of their path, and the particles spiral outward. See also → cyclotron frequency, → synchrotron.

From cyclo- a combining form meaning → cycle + → -tron.

The frequency with which a → non-relativistic particle of charge q and mass m turns in a cyclotron with → uniform magnetic field B. The equality of the → centripetal force to the → Lorentz force leads to the expression: by: f_cycl = qB/2πm. For → relativistic case, the frequency is smaller and is called → synchrotron frequency.

→ cyclotron; → frequency.

Same as → Larmor radius.

→ cyclotron; → radius.

The Swan. A prominent northern → constellation that lies in the glowing band of the Milky way, east of Lyra and north of Vulpecula, and represents a swan. The brightest stars of Cygnus form a cross, so it is also known as the Northern Cross. Abbreviation: Cyg, genitive: Cygni.

From L. cygnus "swan," from Gk. kuknos.

Mâkiyân "a hen, fowl."

The strongest extragalactic radio source in the sky approximately 10⁹ light-years away in the → constellation  → Cygnus. Also called 3C 405.

→ Cygnus.

A large supernova remnant in the → constellation  → Cygnus, some 80 light-years across, lying about 2,500 light-years away. The loop is expanding at over 100 km/s and is thought to be about 30 000 years old.

→ Cygnus, → loop.

One of nine → OB associations located in the Cygnus → constellation. The central association, → Cygnus OB2, is the most famous and the youngest of the Cygnus region. (L. Mahy et al. 2013, astro-ph/1301.0500 and references therein).

→ Cygnus; → OB star; → association.

The nearest example of a → massive star region of → star formation, containing 65 known → O-type stars and hundreds of → B-type stars. Cygnus OB2 lies at a distance of 1.45 → kpc. It is the central association, the most famous, and one of the youngest of the Cygnus region. Cyg OB2 possibly has two → populations with ages of 3.5-5 Myr, while the → O stars seem to belong to a younger population, aged about 2 Myr.

→ Cygnus; → OB association; 2 because there are several OB associations in Cygnus; → Cygnus OB association.

A → binary system containing one of the best candidates for a → black hole. Cygnus X-1 was discovered as an → X-ray source in 1965. It is one of the brightest X-ray sources on the sky, so that it was detected by the earliest → X-ray observation attempts. This binary system, distant of 2.5 kpc, consists of the O9.7 Iab type → supergiant HDE 226868 and a → compact object orbiting around with a period of 5.6 days. The mass of the unseen companion, significantly larger than 5 → solar masses, suggests that it is a black hole. Focused → wind accretion from a → primary star being extremely close to filling the → Roche lobe drives the powerful source of the X-ray radiation.

→ Cygnus.

The surface traced by one side of a rectangle rotating about its parallel side, the latter serving as axis.

From Fr. cylindre, from L. cylindrus "roller, cylinder," from Gk. kylindros "a cylinder, roller, roll," from kylindein "to roll."

Osotvâné, from sotun "column," Mid.Pers. stun, from O.Pers. stênâ "column," Av. stuna-, Skt. sthuna- "column."

Of, pertaining to, or having the form of a cylinder.

From L. cylindricus, from Gk. kylindrikos, see → cylinder; → -ic; → -al.

A coordinate system for a point in space, using an origin (O) and three perpendicular axes (Ox, Oy, Oz), in which a point (P) in space is specified by three numbers ρ, φ, z. The two first numbers, ρ and φ, are → polar coordinates for the vertical projection of P on the xy-plane, and z is the vertical distance of P from the xy-plane.

→ cylindrical; → coordinate.

A lens in which at least one surface is formed like a portion of a cylinder. Also called astigmatic lens.

→ cylinder; → lens.

Referring to the Moon.

From L. Cynthia "the Moon," from Gk. Kynthia "woman from Kynthos." Kynthos was the mountain on Delos on which she and her twin brother Apollo were born.

Mâhi, mângi referring to mâh, mâng, → moon.

Referring to the planet Venus.

From Cythera, in Gk. mythology another name of Aphrodite (Roman equivalent Venus), goddess of love and beauty, since she was believed to emerge from the Mediterranean island Cythera.

Nâhidi referring to Nâhid, planet Venus, Mid.Pers. Anahid "immaculate, unstained," goddess of pure waters and fertility, from Av. arədvi-sûra-anâhita, from arədvi- "increasing, rising," + sûra- "strong, powerful" (Skt. śūra- "valient, courageous") + anâhita "unstained," from an- negation prefix + âhita "spotted."