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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).
Stellar parallax is so difficult to detect that its existence was the subject of much debate in astronomy for hundreds of years. Thomas Henderson, Friedrich Georg Wilhelm von Struve, and Friedrich Bessel made the first successful parallax measurements in 1832–1838, for the stars Alpha Centauri, Vega, and 61 Cygni.
In astronomy, assuming the angle is small (due to a large distance from the Sun), the distance d to a star (measured in parsecs) is the reciprocal of the parallax p (measured in arcseconds): () = / ().
The lower diagram shows an equal angle swept by the Sun in a geostatic model. A similar diagram can be drawn for a star except that the angle of parallax would be minuscule. The most important fundamental distance measurements in astronomy come from trigonometric parallax, as applied in the stellar parallax method. As the Earth orbits the Sun ...
Samuel Birley Rowbotham (/ ˈ r oʊ b ɒ t ə m /; [1] 1816 – 23 December 1884, in London) was an English inventor, writer, utopian socialist [2] and flat Earther who wrote Zetetic Astronomy: Earth Not a Globe under the pseudonym Parallax. His work was originally published as a 16-page pamphlet (1849), and later expanded into a book (1865).
The parsec (parallax arcsecond) is defined in terms of the astronomical unit, being the distance of an object with a parallax of 1″. The light-year is often used in popular works, but is not an approved non-SI unit and is rarely used by professional astronomers. [28]
This is a compilation of symbols commonly used in astronomy, particularly professional astronomy. Age (stellar) τ - age ... parallax; J - epoch; α - Right Ascension ...
Spectroscopic parallax or main sequence fitting [1] is an astronomical method for measuring the distances to stars. Despite its name, it does not rely on the geometric parallax effect. The spectroscopic parallax technique can be applied to any main sequence star for which a spectrum can be recorded.