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The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9 trillion kilometres (19.2 trillion miles).
Distance of the outer limit of Oort cloud from the Sun (estimated, corresponds to 1.2 light-years) — Parsec: 206 265 — One parsec. The parsec is defined in terms of the astronomical unit, is used to measure distances beyond the scope of the Solar System and is about 3.26 light-years: 1 pc = 1 au/tan(1″) [6] [61] Proxima Centauri: 268 000 ...
As a parsec (parallax-second) is defined by the distance of an object that would appear to move exactly one second of arc against background objects, stars less than 5 parsecs away will have measured parallaxes of over 0.2 arcseconds, or 200 milliarcseconds.
Parsecs are used in astronomy to measure interstellar distances. A parsec is approximately 3.26 light-years or about 3.086×10 16 m (1.917×10 13 mi). Combining it with the "atto-" prefix (×10 −18) yields attoparsec (apc), a conveniently human-scaled unit of about 3.086 centimetres (1.215 in) that is used only humorously. [7]
The light-year is most often used when expressing distances to stars and other distances on a galactic scale, especially in non-specialist contexts and popular science publications. [4] The unit most commonly used in professional astronomy is the parsec (symbol: pc, about 3.26 light-years). [2]
Distance traveled by light in vacuum in one year; at its current speed, Voyager 1 would need 17,500 years to travel this distance 10 16: 10 Pm: 30.857 Pm 1 parsec: 39.9 Pm Distance to nearest star (Proxima Centauri) 41.3 Pm As of March 2013, distance to nearest discovered extrasolar planet (Alpha Centauri Bc) 10 17: 100 Pm: 193 Pm
The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A direct distance measurement of an astronomical object is possible only for those objects that are "close enough" (within about a thousand parsecs ) to Earth.
Stellar parallax is the basis for the parsec, which is the distance from the Sun to an astronomical object that has a parallax angle of one arcsecond. (1 AU and 1 parsec are not to scale, 1 parsec = ~206265 AU) Stellar parallax is the apparent shift of position of any nearby star (or other object) against the background of distant stars.