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abstraction > mathematical concept > number > quantity > angle > parallax

parallax (distance)
subject			fact

parallax	has synonym distance
	has definition Angle subtended by the apparent difference in a star's position when viewed from the Earth either simultaneously from opposite sides of the planet, or half such an angle, measured after a gap of six months from opposite sides of the planet's orbit; the nearer the celestial body, the greater the parallax.
	has definition The tiny shift in a star's apparent position that occurs when the star is viewed from slightly different perspectives as the Earth revolves around the Sun. The larger a star's parallax, the closer the star is to Earth.
	has definition The apparent displacement in the position of a star or planet occasioned by its being viewed from two different locations - e.g., by observing it from two widely separated stations on Earth, or at intervals of six months, when the earth is at either extreme of its orbit around the sun. The resulting angle can be used, by triangulation, to determine the distance of the star or planet.
	has definition The difference in apparent direction of an object as seen from two different locations; conversely, the angle at the object that is subtended by the line joining two designated points. Geocentric (diurnal) parallax is the difference in direction between a topocentric observation and a hypothetical geocentric observation. Heliocentric or annual parallax is the difference between hypothetical geocentric and heliocentric observations; it is the angle subtended at the observed object by the semi-major axis of the Earth's orbit. First trigonometric parallax was obtained in 1838. (eee also horizontal parallax.)
	is a kind of angle
angle	has unit angle unit
number	has value

Kinds of parallax :

• dynamical parallax (2 facts) - The "parallax" (i.e., distance) for a binary star whose orbit is well known, derived by using the mass-luminosity relation and Newton's generalization of Kepler's third law.
• horizontal parallax (2 facts) - The difference between the topocentric and geocentric positions of an object, when the object is on the astronomical horizon.
• secular parallax (3 facts) - A parallax based on solar motion; i.e., the baseline is the distance the Sun moves in a given interval of time with respect to the local standard of rest.
• solar parallax (3 facts) - Angle subtended by the equatorial radius of the Earth at a distance of 1 AU.
• stellar parallax