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Encyclopedia > Parsec
1 parsec =
SI units
30.857×1015 m 30.857×1012 km
Astronomical units
206.26×103 AU 3.2616 ly
US customary / Imperial units
101.24×1015 ft 19.174×1012 mi
A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond.
A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond.
See 1 E+16 m for comparable lengths, and scientific notation for an explanation of the notation used in this article.

The parsec (symbol pc) is a unit of length used in astronomy. The length of the parsec is based on the method of trigonometric parallax, one of the oldest methods for measuring the distances to stars. “SI” redirects here. ... This article is about the unit of length. ... “km” redirects here. ... The astronomical unit (AU or au or a. ... A light-year, symbol ly, is the distance light travels in one year: exactly 9. ... U.S. customary units, also known in the United States as English units[1] (but see English unit) or standard units, are units of measurement that are currently used in the USA, in some cases alongside units from SI (the International System of Units — the modern metric system). ... The Imperial units are an irregularly standardized system of units that have been used in the United Kingdom and its former colonies, including the Commonwealth countries. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... “Miles” redirects here. ... Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... This article is about Earth as a planet. ... Astronomical objects are significant physical entities, associations or structures which current science has confirmed to exist in space. ... For other uses, see Parallax (disambiguation). ... A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ... In astronomy, a parsec is a unit of distance. ... To help compare different distances this page lists lengths starting at 1016 m (10 Pm or 67,000 AU, 1. ... Scientific notation, also known as standard form, is a notation for writing numbers that is often used by scientists and mathematicians to make it easier to write large and small numbers. ... The former Weights and Measures office in Middlesex, England. ... Astronomers typically use a number of different length units for different objects. ... For other uses, see Astronomy (disambiguation). ... Wikibooks has a book on the topic of Trigonometry All of the trigonometric functions of an angle θ can be constructed geometrically in terms of a unit circle centered at O. Trigonometry (from Greek trigōnon triangle + metron measure[1]), informally called trig, is a branch of mathematics that deals with... For other uses, see Parallax (disambiguation). ... This article is about the astronomical object. ...


The name parsec stands for "parallax of one second of arc", and one parsec is defined to be the distance from the Earth to a star that has a parallax of 1 arcsecond. The actual length of a parsec is approximately 3.086×1016 m, or about 3.262 light-years, or 473 Octillion, 440 Septillion, 492 sextillion, 351 Quintillion, 307 Quadrillion, 319 Trillion, 996 Billion, 15 Million, 206 Thousand, 787.08 Miles (or 473,440,492,351,307,319,996,015,206,787.08 miles) For other uses, see Parallax (disambiguation). ... A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ... A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ...

Contents

History

The first direct measurements of an object at interstellar distances were undertaken by German astronomer Friedrich Wilhelm Bessel in 1838, who used the width of the Earth's orbit as a baseline to calculate the distance of 61 Cygni using parallax and trigonometry.[1] The parallax of a star is half of the angular distance a star appears to move relative to the celestial sphere as Earth orbits around the Sun; or, equivalently, it is the angle subtended at a star by the semi-major axis of the Earth's orbit. The use of the parsec as a unit of distance follows naturally from this method, since distance (in parsecs) is simply the reciprocal of the parallax angle (in arcseconds). That is, it is the distance at which the semi-major axis of the Earth's orbit would subtend an angle of one second of arc. (See diagram above.) An astronomer or astrophysicist is a person whose area of interest is astronomy or astrophysics. ... Friedrich Wilhelm Bessel (July 22, 1784 – March 17, 1846) was a German mathematician, astronomer, and systematizer of the Bessel functions (which, despite their name, were discovered by Daniel Bernoulli). ... 61 Cygni is a star in the constellation Cygnus. ... For other uses, see Parallax (disambiguation). ... Wikibooks has a book on the topic of Trigonometry All of the trigonometric functions of an angle θ can be constructed geometrically in terms of a unit circle centered at O. Trigonometry (from Greek trigōnon triangle + metron measure[1]), informally called trig, is a branch of mathematics that deals with... In mathematics (in particular geometry and trigonometry) and all natural sciences (including astronomy, geophysics, etc), the angular distance (or angular separation) between two point objects, as observed from a location different from either of these objects, is the size of the angle between the two directions originating from the observer... The celestial sphere is divided by the celestial equator. ... This article is about Earth as a planet. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... Sol redirects here. ... This article is about angles in geometry. ... In mathematics the term subtended usually refers to the direct relationship between an angle and its arc length. ... The reciprocal function: y = 1/x. ...


Though it had probably been used before, the term parsec was first mentioned in an astronomical publication in 1913, when Astronomer Royal Frank Watson Dyson expressed his concern for the need of a name for that unit of distance: he proposes the name astron, but mentions that Carl Charlier had suggested siriometer, and Herbert Hall Turner had suggested parsec.[2] Astronomer Royal is a senior post in the Royal Household of the Sovereign of the United Kingdom. ... Sir Frank Watson Dyson (January 8, 1868 – May 25, 1939) was an English astronomer. ... Carl Vilhelm Ludwig Charlier (April 1, 1862 – November 5, 1934) was a Swedish astronomer. ... Herbert Hall Turner (August 13, 1861 – August 20, 1930) was a British astronomer and seismologist. ...


Usage and Measurement

The parallax method is the fundamental calibration step for distance determination in astrophysics, and the natural unit for such measurements, the parsec, has become the most commonly used unit of distance in scholarly astronomical publications. Articles aimed at a wider audience, such as in newspapers and popular science magazines, often use a more intuitive unit, the light-year (ly). The cosmic distance ladder is the succession of methods by which astronomers determine the distances to celestial objects. ... This article is not about the magazine, Popular Science Popular science is interpretation of science intended for a general audience, rather than for other scientists or students. ... A light-year, symbol ly, is the distance light travels in one year: exactly 9. ...


Other than the Sun, which has a parallax of 90 degrees, there is no known star whose parallax is more than 1 arcsecond. The next closest star is Proxima Centauri with a parallax of 0.77233 arcseconds; it is thus 1.295 pc (4.225 LY) away from the Earth. Sol redirects here. ... Proxima Centauri (Latin proximus, -a, -um: meaning next to or nearest to)[4] is a red dwarf star that is likely a part of the Alpha Centauri star system and is the nearest star to the Sun at a distance of 4. ... A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ...


Refraction caused by the atmosphere, also known as astronomical seeing, limits ground-based telescopes to parallax angle measurement accuracies of less than approximately 0.01 arcsec,[citation needed] so reliable measurements, those with errors of 10% or less, can only be achieved at stellar distances of no more than about 100 pc, or 325 LY. Space-based telescopes are not limited by this effect and can accurately measure distances to objects beyond the limit of ground-based observations. The straw seems to be broken, due to refraction of light as it emerges into the air. ... For other uses, see Atmosphere (disambiguation). ... Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... This article does not cite any references or sources. ...


Between 1989 and 1993, the Hipparcos satellite, launched by the European Space Agency (ESA), measured parallaxes for about 100,000 stars with an astrometric precision of about 0.97 milliarcseconds, and obtained accurate measurements for stellar distances of stars up to 1,000 pc away.[3] NASA's FAME satellite was due to be launched in 2004, to measure parallaxes for about 40 million stars with sufficient precision to measure stellar distances of up to 2,000 pc. However, the mission's funding was withdrawn by NASA in January 2002.[4] ESA's GAIA satellite, due to be launched in December 2011, is intended to measure one billion stellar distances to within 20 microarcseconds, producing errors of 10% in measurements as far as the Galactic Center, about 8,000 pc away in the constellation of Sagittarius.[5] Hipparcos (for High Precision Parallax Collecting Satellite) was an astrometry mission of the European Space Agency (ESA) dedicated to the measurement of stellar parallax and the proper motions of stars. ... “ESA” redirects here. ... Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ... This article is about the American space agency. ... Gaia is an astrometry space mission, and a successor to the ESA Hipparcos mission. ... For the series of books, see Galactic Center Saga. ... This article is about the star grouping. ... For other uses, see Sagittarius. ...


Distances in parsecs

Distances less than a parsec

Distances measured in fractions of a parsec usually involve objects within a single star system. So, for example: In common usage a fraction is any part of a unit. ...

  • one astronomical unit (AU) - the distance from the Sun to the Earth - is 4.85×10-6 pc.
  • the most distant space probe, Voyager 1, was 4.6×10-4 pc away from Earth in September 2004. It took Voyager 27 years to cover that distance.
  • the Oort cloud is postulated to be approximately 0.6 pc in diameter.

The astronomical unit (AU or au or a. ... Sol redirects here. ... This article is about Earth as a planet. ... Technicians work on the Ulysses space probe. ... For the album by The Verve, see Voyager 1 (album). ... 2004 is a leap year starting on Thursday of the Gregorian calendar. ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ...

Parsecs and kiloparsecs

Distances measured in parsecs include distances between nearby stars, such as those in the same spiral arm or globular cluster. A distance of one thousand parsecs (approximately 3,262 ly) is commonly denoted by the kiloparsec (kpc). Astronomers typically use kiloparsecs to measure distances between parts of a galaxy, or within groups of galaxies. So, for example: This article is about the astronomical object. ... A spiral galaxy presents a face-on view of its spiral arms. ... The Globular Cluster M80 in the constellation Scorpius is located about 28,000 light years from the Sun and contains hundreds of thousands of stars. ... For other uses, see Galaxy (disambiguation). ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ...

  • one parsec is approximately 3.262 light-years.
  • the nearest known star to the Earth, other than the Sun, is Proxima Centauri, 1.29 parsecs away.
  • the center of the Milky Way is about 8 kpc from the Earth, and the Milky Way is about 30 kpc across.
  • the Andromeda Galaxy (M31), the most distant object visible to the naked eye, is a little under 800 kpc away from the Earth.

Proxima Centauri (Latin proximus, -a, -um: meaning next to or nearest to)[4] is a red dwarf star that is likely a part of the Alpha Centauri star system and is the nearest star to the Sun at a distance of 4. ... For the series of books, see Galactic Center Saga. ... For other uses, see Milky Way (disambiguation). ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... The Messier objects are a set of astronomical objects catalogued by Charles Messier in his catalogue of Nebulae and Star Clusters first published in 1774. ...

Megaparsecs and gigaparsecs

A distance of one million parsecs (approximately 3,262,000 ly or 2×1019 miles) is commonly denoted by the megaparsec (Mpc). Astronomers typically measure the distances between neighboring galaxies and galaxy clusters in megaparsecs. Look up million in Wiktionary, the free dictionary. ... For other uses, see Galaxy (disambiguation). ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ...


Galactic distances are sometimes given in units of Mpc/h (as in "50/h Mpc"). h is a parameter in the range [0.5,0.75] reflecting the uncertainty in the value of the Hubble constant for the rate of expansion of the universe (H = 100h km/s/Mpc). The Hubble constant becomes relevant when converting an observed redshift z into a distance using the formula dc / Hz (where c is the velocity of light)[6]. Hubbles law is the statement in astronomy that the redshift in light coming from distant galaxies is proportional to their distance. ... Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared with that of the Sun (left). ...


One gigaparsec (Gpc) is one billion parsecs — one of the largest distance measures commonly used. One gigaparsec is about 3.262 billion light-years, or roughly one fourteenth of the distance to the horizon of the observable universe (dictated by the cosmic background radiation). Astronomers typically use gigaparsecs to measure large-scale structures such as the size of and distance to the Great Wall, the distances between clusters of galaxies, and the distance to quasars. One thousand million (1,000,000,000) is the natural number following 999,999,999 and preceding 1,000,000,001. ... Horizon. ... When any patch of the sky is observed where no individual sources can be discerned, and the effects of interplanetary dust, and interstellar matter are taken into account, there is still radiation. ... Astronomy and cosmology examine the universe to understand the large-scale structure of the cosmos. ... The Great Wall is the largest known super-structure in the Universe. ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...


For example:

The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ... A sky field near some of the brighter galaxies in the Virgo cluster. ... RXJ1242-11 (also known as Galaxy RXJ1242-11) is a galaxy located approximately 200 megaparsecs from Earth. ... For the song by Muse, see Supermassive Black Hole (song). ... For other uses, see Milky Way (disambiguation). ... It has been suggested that this article or section be merged into Observable universe. ... For other uses, see Universe (disambiguation). ... See universe for a general discussion of the universe. ...

Calculating the value of a parsec

Diagram of parsec. ...


In the diagram above (not to scale), S represents the Sun, and E the Earth at one point in its orbit. D is an object at a distance of one parsec from the Sun. By definition, the angle D is one arcsecond, and the distance ES is one astronomical unit (AU). By trigonometry, the distance SD is Sol redirects here. ... This article is about Earth as a planet. ... A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ... The astronomical unit (AU or au or a. ... Wikibooks has a book on the topic of Trigonometry All of the trigonometric functions of an angle θ can be constructed geometrically in terms of a unit circle centered at O. Trigonometry (from Greek trigōnon triangle + metron measure[1]), informally called trig, is a branch of mathematics that deals with...

One AU = 149,597,870.7 km, so 1 parsec = 30,856,775,813,057.3 km ≈ 30.857×1015 meters ≈ 3.26163626 light-years. A light-year, symbol ly, is the distance light travels in one year: exactly 9. ...


Parsecs in popular culture

Parsecs have been mentioned in many science fiction novels (the works of Isaac Asimov for example), television series (Star Trek, Futurama, and others), and a number of films. Isaac Asimov (January 2?, 1920?[1] – April 6, 1992), IPA: , originally Исаак Озимов but now transcribed into Russian as Айзек Азимов) was a Russian-born American Jewish author and professor of biochemistry, a highly successful and exceptionally prolific writer best known for his works of science fiction and for his popular science books. ... The current Star Trek franchise logo Star Trek is an American science fiction entertainment series and media franchise. ... This article is about the television series. ...


The most famous use (or misuse) is from Star Wars: A New Hope. In the Mos Eisley Cantina, Han Solo refers to the Millennium Falcon as "the ship that made the Kessel Run in less than 12 parsecs". It is not clear whether the unit is being used to measure time or distance in this context. However, later novels in this fictional universe attributed this claim to the ability of the Millennium Falcon to reach the planet Kessel in the shortest distance despite having to pass near a very dangerous region of space, The Maw, populated by numerous black holes. This shorter course would require them to cut closer to the black holes of The Maw, implying a higher ship speed to avoid the stronger gravitational forces involved in the route. This movie poster for Star Wars depicts many of the films important elements, such as Luke Skywalker, Princess Leia, Han Solo, X-Wing and Y-Wing fighters Star Wars, retitled Star Wars Episode IV: A New Hope in 1981 (see note at Title,) is the original (and in chronological... Han Solo is a character in the Star Wars universe. ... The Millennium Falcon is a fictional spacecraft in the Star Wars universe commanded by smuggler Han Solo (Harrison Ford) and his Wookiee firstmate, Chewbacca (Peter Mayhew). ...


The Star Wars usage of parsec was parodied in the Family Guy episode "Blue Harvest" where Peter as Han Solo is questioned by Chris as Luke on whether it is, in fact, a measure of distance. Family Guy is an Emmy award winning American animated television series about a nuclear family in the fictional town of Quahog (IPA or ), Rhode Island. ... “Blue Harvest” is the hour-long (with commercials) sixth-season premiere episode of the FOX animated television series Family Guy. ... Peter Löwenbräu Griffin is the protagonist in the American animated television series Family Guy. ... Han Solo is a character in the Star Wars universe. ... Christopher Cross Chris Griffin (born 1993, in Quahog, Rhode Island) is the second child of Peter and Lois Griffin in the TV cartoon series Family Guy. ... Luke Ballard is a fictional character in the Star Wars universe, portrayed by Mark Hamill in the films Star Wars Episode IV: A New Hope, Star Wars Episode V: The Empire Strikes Back, and Star Wars Episode VI: Return of the Jedi. ...


Stephen Colbert's Tek Jansen character often says he will be back in "three parsecs", incorrectly using the term as a measure of time. This article is about Stephen Colbert, the actor. ... Tek Jansen is a fictional character featured on The Colbert Report and in a comic book series published by Oni Press. ...


In the novel A Wrinkle in Time by Madeleine L'Engle, Dr. Alexander Murry's nickname for his daughter Meg (Margaret) Murry is "Megaparsec". For the movie adaptation, see A Wrinkle in Time (film) . A Wrinkle in Time is a science fantasy[1] novel by Madeleine LEngle, written between 1959 and 1960[2] and published in 1962 after at least 26 rejections by publishers[3] because it was, in LEngles words... Madeleine LEngle (November 29, 1918 – September 6, 2007)[1] was an American writer best known for her childrens books, particularly the Newbery Medal-winning A Wrinkle in Time and its sequels A Wind in the Door, A Swiftly Tilting Planet and Many Waters. ...


When the ship takes on a mind of its own in Futurama and heads toward a gigantic quasar in order to squish her and Bender together, Leela says, "Sweety, maybe you wanna move a few parsecs to the left?" This article is about the television series. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Bender Bending Rodríguez, more commonly known as Bender (assembled c. ... Turanga Leela (often referred to simply as Leela) (born A.D. 2975) is the primary female character in the animated television series Futurama. ...


In the movie Abraxas, Guardian of the Universe, one character chastises another saying, "a parsec is not an acceptable unit of time measurement on Earth." Abraxas, Guardian of the Universe is a 1991 science-fiction/action film written and directed by Damian Lee and starring Jesse The Body Ventura and Sven-Ole Thorsen, with a cameo by James Belushi. ...


References

is the 250th day of the year (251st in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ...

Notes

  1. ^ Bessel, FW, "Bestimmung der Entfernung des 61sten Sterns des Schwans" (1838) Astronomische Nachrichten, Vol.16, p.65-96.
  2. ^ Dyson, F. W., "The distribution in space of the stars in Carrington's Circumpolar Catalogue" (1913) Monthly Notices of the Royal Astronomical Society, Vol. 73, p.334-342; see footnote on p.342.
  3. ^ The Hipparcos Space Astrometry Mission. Retrieved on Aug 28, 2007.
  4. ^ FAME news, 25 January 2002.
  5. ^ GAIA from ESA.
  6. ^ Galaxy structures: the large scale structure of the nearby universe. Retrieved on May 22, 2007.

Astronomische Nachrichten (Astronomical Notes), one of the first international journals in the field of astronomy,[1] was founded in 1821 by the German astronomer Heinrich Christian Schumacher. ... Monthly Notices of the Royal Astronomical Society (MNRAS) is one of the worlds leading scientific journals in astronomy and astrophysics. ... August 28 is the 240th day of the year in the Gregorian Calendar (241st in leap years), with 125 days remaining. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 25th day of the year in the Gregorian calendar. ... Also see: 2002 (number). ... This article is about the European Space Agency. ... is the 142nd day of the year (143rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ...

See also


  Results from FactBites:
 
Parsec - Wikipedia, the free encyclopedia (907 words)
One parsec is defined to be the distance from the Earth to a star that has a parallax of 1 arcsecond.
The parsec follows naturally from this method, since the distance (in parsecs) is simply the reciprocal of the parallax angle (in arcseconds).
The Oort cloud is approximately 0.6 parsec in diameter.
Parsec, Parsec definition, Parsec Enterprises, Sam Younghans (1853 words)
The parsec equals 3.26 light-years; 206,265 astronomical units; 3.086 X (10 to the power of 13) kilometers; or 1.917 X (10 to the power of 13) miles.
Professor Turner suggests Parsec, which may be taken as an abbreviated form of `a distance corresponding to a parallax of one second'.
A unit of stellar measurement is the parsec; it is the distance at which a star would have a parallax of one second of arc and is equivalent to 206,265 times the distance from the earth to the sun, or about 3.3 light-years.
  More results at FactBites »

 
 

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