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

1) Having the form of a circle.
2) Moving in or forming a circle or a circuit.

M.E. circuler, O.Fr. circuler, from L. circularis, from circulus, → circle, + -aris "-ar," variant of → -al, joined to words in which an l precedes the suffix (circular; lunar; singular).

Dâyere-yi, parhuni, from dâyeré or parhun→ circle + -i adj. suffix.

A → magnetic field whose lines of force (→ line of force) run around the perimeter of the magnet.

→ circular; → magnetic; → field.

Motion in which an object moves in a circle at a constant speed. The velocity, however, changes not because the magnitude of the velocity changes, but because its direction changes. The changing velocity creates an acceleration, called → centripetal acceleration. This acceleration results from the → centripetal force.

→ circular; → motion.

The path of a object in → circular motion.

→ circular; → orbit.

The → polarization of an → electromagnetic radiation in which the electric field vector describes a circle about the direction of propagation at any point in the path of the radiation. Circular polarization is a combination of two perpendicular → linearly polarized waves that are 90 degrees out of phase with each other. Circular polarization may be referred to as "right-hand" or "left-hand," depending on the rotation direction as viewed by the observer.

→ circular; → polarization.

Circular band-pass interference filter whose thickness and central wavelength vary along the perimeter. They are used in low-resolution spectrophotometers mainly in the infra-red.

→ circular; → variable; → filter.

Light exhibiting → circular polarization.

→ circular; → polarized; → light.

The smallest → circular orbit in which a particle can stably orbit a → black hole according to → general relativity without the risk of falling past the → event horizon. In other words, the ISCO is the inner edge of the → accretion disk around a black hole. Therefore, characteristics of accretion disks depend on ISCO. The radius of ISCO is calculated to be three times the → Schwarzschild radius (3 R_Sch). ISCO is closer to event horizon for rotating black hole.

→ inner; → stable; → circular; → orbit.

The motion of an object around a fixed point at a constant angular speed, and at constant radius.

→ uniform; → circular; → motion.