Now, if the angle formed between the line drawn from the object to the Earth and the line drawn from the object to the Sun is exactly one arcsecond, then the object's distance from the Sun would be exactly one parsec. In other words, imagine that a straight line is drawn from the object to the Earth, a second line is drawn from the Earth to the Sun, and a third line is drawn from the object to the Sun that is perpendicular to the line drawn from the Earth to the Sun. A parsec is the distance from the Sun to an astronomical object which has a parallax angle of one arcsecond. The name parsec is "an abbreviated form of 'a distance corresponding to a parallax of one arcsecond'." It was coined in 1913 at the suggestion of British astronomer Herbert Hall Turner. The parsec is a unit of length used in astronomy, equal to about 30.9 trillion kilometres or 3.26 light-years. This corresponds to the small-angle definition of the parsec found in many astronomical references.įreebase Rate this definition: 0.0 / 0 votes In August 2015, the International Astronomical Union (IAU) passed Resolution B2 which, as part of the definition of a standardized absolute and apparent bolometric magnitude scale, mentioned an existing explicit definition of the parsec as exactly 648000/π au, or approximately 30.856775814913673×1015 metres (based on the IAU 2012 exact SI definition of the astronomical unit).
Although parsecs are used for the shorter distances within the Milky Way, multiples of parsecs are required for the larger scales in the universe, including kiloparsecs (kpc) for the more distant objects within and around the Milky Way, megaparsecs (Mpc) for mid-distance galaxies, and gigaparsecs (Gpc) for many quasars and the most distant galaxies. Partly for this reason, it is the unit preferred in astronomy and astrophysics, though the light-year remains prominent in popular science texts and common usage. Most stars visible to the naked eye are within a few hundred parsecs of the Sun, with the most distant at a few thousand.The word parsec is a portmanteau of "parallax of one second" and was coined by the British astronomer Herbert Hall Turner in 1913 to make calculations of astronomical distances from only raw observational data easy for astronomers. The nearest star, Proxima Centauri, is about 1.3 parsecs (4.2 light-years) from the Sun. This corresponds to 648000/π astronomical units, i.e. 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 (1/3600 of a degree).
30.9 trillion kilometres (19.2 trillion miles). 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. Wikipedia Rate this definition: 0.0 / 0 votes
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