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

A diffraction grating placed over the aperture of a telescope in order to produce spectra of all the objects in the field of view.

→ objective; → grating.

The lens or system of lenses in a → telescope or → microscope that magnify an object and project a larger → image. The object lens is nearest the object being viewed

→ objective; → lens.

A dispersing prism placed in front of a telescope objective to produce spectra of all luminous objects in the field of view.

→ objective; → prism.

A probability determined by the long-term frequency of an event; in contrast to subjective probability.

→ objective; → probability.

1) The state or quality of being → objective. Opposite of → subjectivity.
2) Ability to view things objectively.
3) External reality.

→ objective + → -ity.

Adjective meaning flattened, as → oblate spheroid. Opposed to → prolate.

From L. ob- "toward" + latus, abstracted from its opposite, prolatus "lengthened."

Pax "oblate," of unknown etymology.

An ellipsoid produced by rotating an ellipse through 360° about its minor axis. Compare with → prolate spheroid.

→ oblate; → spheroid.

The property possessed by a round body that is flattened at the poles.

Noun from → oblate.

1a) To bind or oblige morally or legally.
1b) To pledge, commit, or bind (funds, property, etc.) to meet an obligation.
2a) Morally or legally bound; obliged; constrained.
2b) Necessary; essential (Dictionary.com).

Back-formation from → obligation.

1) Something by which a person is bound or obliged to do certain things, and which arises out of a sense of duty or results from custom, law, etc.
2) Something that is done or is to be done for such reasons (Dictionary.com).

M.E. obligacioun, from O.Fr. obligacion "obligation, duty, responsibility," from L. obligationem "an engaging or pledging," literally "a binding," noun of action from p.p. stem of obligare "to bind, bind up, bandage," from → ob- "to" + ligare "to bind," from PIE root *leig- "to bind."

Fariz, from Mid.Pers. frêz "obligation; duty."

Required as a matter of obligation; mandatory; incumbent; compulsory.

M.E., from L.L. obligatorius "binding," → obligate, + -tory, from L. -torius, from → -tor + -ius.

Farizgun, from fariz, → duty, + -gun "manner, fashion."

Neither perpendicular nor horizontal; having the axis not perpendicular to the base; slanting; sloping.

From M.Fr. oblique, from L. obliquus "slanting, sidelong, indirect," from ob "against" + root of licinus "(of an ox whose corn tips are) bent upward," from PIE base *lei- "to bend, be movable."

Yekvar, literally "slantingn to a side," from yek-, → one, + var "side," variant bar "side; breadth; breast" (Mid.Pers. var "breast;" Av. vouru "wide, broad, extended" (vourucašāni- "looking far"), related to varah- "breast;" cf. Skt. urú- "wide, broad," úras- "breast;" Gk. eurus "wide, broad;" PIE base uer-, ueru-s"wide, broad").

A stellar model in which the rotation axis is tilted relative to the magnetic dipole axis. As the star rotates, observable quantities (e.g. the line-of-sight component of the magnetic field, stellar brightness, emission lines) are modulated according to the rotational period. Such a model was first put forward by D. Stibbs (1950, MNRAS, 110, 395).

→ oblique; → rotator; → model.

A → shock wave that is inclined to the flow direction. Depending on the shape of the object and the speed of the → flow, the shock wave may be inclined to the flow direction.

→ oblique; → shock.

The celestial sphere when the circles parallel to the equator are cut obliquely by the horizon plane, which divides them into two unequal parts. In other words, the sphere when its axis is oblique to the horizon of the place.

→ oblique; → sphere.

1) General: The quality or state of being oblique.
2) The → angle that an object's → rotational axis makes with its → orbital axis. In other words, the angle between its → equatorial plane and → orbital plane. Same as → axial tilt.

State noun of → oblique.

The angle between the Earth's → equatorial plane and the → ecliptic. Its present value is 23°26'13.5'' (or 23.43708 degrees). The effects of → precession and → nutation cause it to change between extreme values of 22.1 and 24.5 degrees over a period of approximately 41,000 years. It is currently decreasing.

→ obliquity; → ecliptic.

Elongated, usually from the square or circular form.

Late M.E. oblonge, from L. oblongus "rather long," from ob- a prefix meaning "toward, to, on, over, against" + longus, → long.

Derâzak, from derâz "long," → length + -ak suffix.

A → nitrogen (N)-rich → O-type or → B-type star.

→ O star; → B star; → nitrogen; → star.

1) Opposition to the spread of knowledge; a policy of withholding knowledge from the general public.
2) A style (as in literature or art) characterized by deliberate vagueness or abstruseness (Merriam-Webster.com).

From Fr. obscurantisme (1819), from obscurant, from obscure, from L. obscurus "dark, dusky," figuratively "unknown; unintelligible," from ob- "over" + -scurus "covered," from PIE *(s)keu- "to cover, conceal;" → -ism.