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[a] The parsec unit is obtained by the use of parallax and trigonometry, and is defined as the distance at which 1 AU subtends an angle of one arcsecond [1] ( 1 / 3600 of a degree). The nearest star, Proxima Centauri , is about 1.3 parsecs (4.2 light-years) from the Sun : from that distance, the gap between the Earth and the Sun spans ...
The unit most commonly used in professional astronomy is the parsec (symbol: pc, about 3.26 light-years). [2] ... 1 light-year = 9 460 730 472 580 800 metres (exactly)
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 ...
The star, whose mass is roughly half that of the Sun, is currently 62 light-years from the Solar System. It was first noticed in 1999 using data from the Hipparcos satellite, and was estimated to pass less than 1.3 light-years (0.40 pc) from the Sun in 1.4 million years. [73]
The parsec (3.26 light-years) is defined as the distance for which the annual parallax is 1 arcsecond. Annual parallax is normally measured by observing the position of a star at different times of the year as Earth moves through its orbit. The angles involved in these calculations are very small and thus difficult to measure.
A parsec is the distance from the Sun to an astronomical object that has a parallax angle of one arcsecond (not to scale). 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).
The amount of shift is quite small, even for the nearest stars, measuring 1 arcsecond for an object at 1 parsec's distance (3.26 light-years), and thereafter decreasing in angular amount as the distance increases. Astronomers usually express distances in units of parsecs (parallax arcseconds); light-years are used in popular media.
15 Pm – 1.59 light-years – possible outer radius of Oort cloud; 20 Pm – 2.11 light-years – maximum extent of influence of the Sun's gravitational field [citation needed] 30.9 Pm – 3.26 light-years – 1 parsec; 39.9 Pm – 4.22 light-years – distance to Proxima Centauri (nearest star to Sun) 81.3 Pm – 8.59 light-years – distance ...