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{{Short description|Mean distance between Earth and the Sun, common length reference in astronomy}}
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[[Датотека:Astronomical unit.png|мини|Астрономска јединица]]
{{Infobox unit
'''Астрономска јединица''' ('''АЈ''') ({{јез-енгл|Astronomical unit ('''AU''')}}; симбол: -{'''au'''}- или -{'''ua'''}-) мера је за удаљеност једнака просечној удаљености [[Земља|Земље]] од [[Сунце|Сунца]]. Данас прихваћена мера за АЈ је 149.597.870.691 [[метар]]а (приближно 149.600.000 -{km}-). Ово растојање добија се једноставним рачуном узимајући у обзир да нам је паралакса Сунца позната (тј. можемо је измерити) и износи око 8,794145 лучних секунди.
| bgcolour =
| name = Астрономска јединица
| image= File:Astronomical unit.png
| caption= Сива линија означава удаљеност Земља-Сунце, која је у просеку око 1 астрономске јединице.
| standard = [[Astronomical system of units|Астрономски систем јединица]]<br/>[[Non-SI units mentioned in the SI|(Прихваћено за употребу са СИ)]]
| quantity = [[дужина]]
| symbol = ај или {{sc|au}} или АЈ
| units1 = [[metric system|метеричке]] ([[International System of Units|СИ]]) јединице
| inunits1 = {{val|1.495978707|e=11|ul=m}}
| units2 = [[Imperial units|империјалне]]&nbsp;&&nbsp;[[United States customary units|УС]]&nbsp;јединице
| inunits2 ={{val|9.2956|e=7|ul=mi}}
| units3 = [[Astronomical system of units|астрономске јединице]]
| inunits3 = {{val|4.8481|e=-6|ul=pc}}<br/>&nbsp;&nbsp;&nbsp;{{val|1.5813|e=-5|ul=ly}}
}}


'''Астрономска јединица''' ('''АЈ''') ({{јез-енгл|Astronomical unit ('''AU''')}}; симбол: -{'''au'''}- или -{'''ua'''}-)<ref name="IAUresB2">{{cite conference |title=On the re-definition of the astronomical unit of length |id=Resolution&nbsp;B2 |conference=XXVIII&nbsp;General Assembly of International Astronomical Union |publisher=International Astronomical Union |place=Beijing, China |date=31 August 2012 | url = http://www.iau.org/static/resolutions/IAU2012_English.pdf |quote=... recommends ... 5. that the unique symbol "au" be used for the astronomical unit.}}</ref><ref name="mnras_style">{{cite web | url=http://www.oxfordjournals.org/our_journals/mnras/for_authors/#6.4%20Miscellaneous%20journal%20style | archive-url=https://web.archive.org/web/20121022064348/http://www.oxfordjournals.org/our_journals/mnras/for_authors/#6.4%20Miscellaneous%20journal%20style | url-status=dead | archive-date=22 October 2012 | title=Monthly Notices of the Royal Astronomical Society: Instructions for Authors | website=Oxford Journals | access-date=20 March 2015 | quote=The units of length/distance are Å, nm, μm, mm, cm, m, km, au, light-year, pc.}}</ref><ref name="AAS_style" /> мера је за удаљеност једнака просечној удаљености [[Земља|Земље]] од [[Сунце|Сунца]]. Данас прихваћена мера за АЈ је 149.597.870.691 [[метар]]а (приближно 149.600.000 -{km}-).<ref>{{cite conference |id=Resolution B2 |title=On the re-definition of the astronomical unit of length |publisher=International Astronomical Union |conference=XXVIII&nbsp;General Assembly of International Astronomical Union |place=Beijing |date=31 August 2012 |url=http://www.iau.org/static/resolutions/IAU2012_English.pdf |quote=... recommends [adopted] that the astronomical unit be re-defined to be a conventional unit of length equal to exactly 149,597,870,700&nbsp;metres, in agreement with the value adopted in IAU&nbsp;2009 Resolution&nbsp;B2}}</ref> Ово растојање добија се једноставним рачуном узимајући у обзир да нам је паралакса Сунца позната (тј. можемо је измерити) и износи око 8,794145 лучних секунди. Користи се често у астрономији за међупланетска растојања, тј. у оквиру [[Сунчев систем|Сунчевог система]] или других [[планетарни систем|планетарних система]]. За међузвездана растојања користе се веће јединице, [[светлосна година]] и [[парсек]].<ref name=au_parsec>{{cite journal |author1=Luque, B. |author2=Ballesteros, F.J. |year=2019 |title=Title: To the Sun and beyond |journal=[[Nature Physics]] |volume=15 |page=1302 |doi=10.1038/s41567-019-0685-3 |doi-access=free}}</ref>
Користи се често у астрономији за међупланетска растојања, тј. у оквиру [[Сунчев систем|Сунчевог система]] или других [[планетарни систем|планетарних система]]. За међузвездана растојања користе се веће јединице, [[светлосна година]] и [[парсек]].

== Историја употребе симбола ==
{{рут}}
A variety of unit symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the [[International Astronomical Union]]&nbsp;(IAU) had used the symbol ''A'' to denote a length equal to the astronomical unit.<ref name="IAU76" /> In the astronomical literature, the symbol AU was (and remains) common. In 2006, the [[International Bureau of Weights and Measures]] (BIPM) had recommended ua as the symbol for the unit.<ref name="Bureau International des Poids et Mesures 2006 126">{{citation |author=Bureau International des Poids et Mesures |author-link=Bureau International des Poids et Mesures |date=2006 |title=The International System of Units (SI) |edition=8th |publisher=Organisation Intergouvernementale de la Convention du Mètre |page=126 |url=http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf}}</ref> In the non-normative Annex&nbsp;C to [[ISO 80000-3]]:2006 (now withdrawn), the symbol of the astronomical unit was "ua".

In 2012, the IAU, noting "that various symbols are presently in use for the astronomical unit", recommended the use of the symbol "au".<ref name="IAUresB2" /> The [[scientific journal]]s published by the [[American Astronomical Society]] and the [[Royal Astronomical Society]] subsequently adopted this symbol.<ref name="AAS_style">{{cite web |title=Manuscript Preparation: AJ & ApJ Author Instructions |website=American Astronomical Society |url=http://aas.org/authors/manuscript-preparation-aj-apj-author-instructions#_Toc2.2 |access-date=29 October 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160221121728/http://aas.org/authors/manuscript-preparation-aj-apj-author-instructions#_Toc2.2 |archive-date=21 February 2016 |quote=Use standard abbreviations for ... natural units (e.g., au, pc, cm).}}</ref><ref>{{cite web |title=Instructions to Authors |website=Monthly Notices of the Royal Astronomical Society |publisher=Oxford University Press |url=https://academic.oup.com/mnras/pages/General_Instructions |access-date=5 November 2020 |quote=The units of length/distance are Å, nm, µm, mm, cm, m, km, au, light-year, pc.}}</ref> In the 2014 revision and 2019 edition of the SI Brochure, the BIPM used the unit symbol "au".<ref name=SI_Brochure2012>{{cite web |orig-year=2006 |year=2014 |title=The International System of Units (SI) |edition=8th |publisher=BIPM |series=SI Brochure |url=http://www.bipm.org/en/publications/si-brochure/table6.html |access-date=3 January 2015}}</ref><ref name=SI_Brochure2019>{{cite web |url=https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9-EN.pdf |series=SI Brochure |title=The International System of Units (SI) |edition=9th |year=2019 |publisher=BIPM |page = 145 |access-date=1 July 2019}}</ref> ISO&nbsp;80000-3:2019, which replaces ISO&nbsp;80000-3:2006, does not mention the astronomical unit.<ref>{{cite web |title=ISO 80000-3:2019 |url=https://www.iso.org/standard/64974.html |publisher=[[International Organization for Standardization]] |access-date=2020-07-03}}</ref><ref>{{cite web |id=ISO&nbsp;80000-3:2019(en) |series=Quantities and units |title=Part&nbsp;3: Space and time |url=https://www.iso.org/obp/ui/#iso:std:iso:80000:-3:ed-2:v1:en |publisher=[[International Organization for Standardization]] |access-date=2020-07-03}}</ref>

== Развој дефиниције јединице ==

[[Earth's orbit]] around the Sun is an [[ellipse]]. The [[semi-major axis]] of this [[elliptic orbit]] is defined to be half of the straight [[line segment]] that joins the [[perihelion and aphelion]]. The centre of the Sun lies on this straight line segment, but not at its midpoint. Because ellipses are well-understood shapes, measuring the points of its extremes defined the exact shape mathematically, and made possible calculations for the entire orbit as well as predictions based on observation. In addition, it mapped out exactly the largest straight-line distance that Earth traverses over the course of a year, defining times and places for observing the largest [[parallax]] (apparent shifts of position) in nearby stars. Knowing Earth's shift and a star's shift enabled the star's distance to be calculated. But all measurements are subject to some degree of error or uncertainty, and the uncertainties in the length of the astronomical unit only increased uncertainties in the stellar distances. Improvements in precision have always been a key to improving astronomical understanding. Throughout the twentieth century, measurements became increasingly precise and sophisticated, and ever more dependent on accurate observation of the effects described by [[Albert Einstein|Einstein]]'s [[theory of relativity]] and upon the mathematical tools it used.

Improving measurements were continually checked and cross-checked by means of improved understanding of the laws of [[celestial mechanics]], which govern the motions of objects in space. The expected positions and distances of objects at an established time are calculated (in au) from these laws, and assembled into a collection of data called an [[ephemeris]]. [[NASA]]{{'s}} [[Jet Propulsion Laboratory]] HORIZONS System provides one of several ephemeris computation services.<ref name=Horizons>{{cite web |title=HORIZONS System |url=http://ssd.jpl.nasa.gov/?horizons |work=Solar system dynamics |date=4 January 2005 |access-date=16 January 2012 |publisher=NASA: Jet Propulsion Laboratory}}</ref>

In 1976, to establish an even precise measure for the astronomical unit, the IAU formally [[IAU (1976) System of Astronomical Constants|adopted a new definition]]. Although directly based on the then-best available observational measurements, the definition was recast in terms of the then-best mathematical derivations from celestial mechanics and planetary ephemerides. It stated that "the astronomical unit of length is that length (''A'') for which the [[Gaussian gravitational constant]] (''k'') takes the value {{val|0.01720209895}} when the units of measurement are the astronomical units of length, mass and time".<ref name="IAU76">{{cite conference |title=item&nbsp;12: Unit distance |series=IAU (1976) System of Astronomical Constants |author=Commission&nbsp;4: Ephemerides/Ephémérides |id=Commission&nbsp;4, part&nbsp;III, Recommendation&nbsp;1, item&nbsp;12 <!-- Resolution No.&nbsp;10 --> |url=http://www.iau.org/static/resolutions/IAU1976_French.pdf |conference=XVIth General Assembly of the International Astronomical Union |place=Grenoble, FR |year=1976}}</ref><ref name="Trümper">{{cite book |title=Astronomy, astrophysics, and cosmology – Volume VI/4B ''Solar System'' |chapter-url=https://books.google.com/books?id=wgydrPWl6XkC&pg=RA1-PA4 |page=4 |date=2009 |author1=Hussmann, H. |author2=Sohl, F. |author3=Oberst, J. |chapter=§&nbsp;4.2.2.1.3: Astronomical units |editor=Trümper, Joachim E. |isbn=978-3-540-88054-7 |publisher=Springer}}</ref><ref name= Fairbridge>{{cite book |title=Encyclopedia of planetary sciences |author=Williams Gareth V. |editor1=Shirley, James H. |editor2=Fairbridge, Rhodes Whitmore |chapter=Astronomical unit |chapter-url=https://books.google.com/books?id=dw2GadaPkYcC&pg=PA48 |page=48 |isbn=978-0-412-06951-2 |date=1997 |publisher=Springer}}</ref> Equivalently, by this definition, one au is "the radius of an unperturbed circular Newtonian orbit about the sun of a particle having infinitesimal mass, moving with an [[angular frequency]] of {{val|0.01720209895|u=radians per day}}";<ref name=SIbrochure>{{SIbrochure8th|page=126}}</ref> or alternatively that length for which the [[standard gravitational parameter|heliocentric gravitational constant]] (the product ''G''{{Solar mass}}) is equal to ({{val|0.01720209895}})<sup>2</sup>&nbsp;au<sup>3</sup>/d<sup>2</sup>, when the length is used to describe the positions of objects in the Solar System.

Subsequent explorations of the Solar System by [[space probe]]s made it possible to obtain precise measurements of the relative positions of the [[Solar System#Inner planets|inner planets]] and other objects by means of [[radar]] and [[telemetry]]. As with all radar measurements, these rely on measuring the time taken for [[photons]] to be reflected from an object. Because all photons move at the [[speed of light]] in vacuum, a fundamental constant of the universe, the distance of an object from the probe is calculated as the product of the speed of light and the measured time. However, for precision the calculations require adjustment for things such as the motions of the probe and object while the photons are transiting. In addition, the measurement of the time itself must be translated to a standard scale that accounts for relativistic time dilation. Comparison of the ephemeris positions with time measurements expressed in [[Barycentric Dynamical Time]]&nbsp;(TDB) leads to a value for the speed of light in astronomical units per day (of {{val|86400|u=second}}). By 2009, the IAU had updated its standard measures to reflect improvements, and calculated the speed of light at {{val|173.1446326847|(69)|u=au/d}} (TDB).<ref>{{cite book |chapter-url=http://asa.usno.navy.mil/static/files/2009/Astronomical_Constants_2009.pdf |chapter=Selected Astronomical Constants |title=The Astronomical Almanac Online |publisher=[[United States Naval Observatory|USNO]]–[[United Kingdom Hydrographic Office|UKHO]] |page=K6 |date=2009 |archive-url=https://web.archive.org/web/20140726132053/http://asa.usno.navy.mil/static/files/2009/Astronomical_Constants_2009.pdf|archive-date=26 July 2014}}</ref>

In 1983, the CIPM modified the [[International System of Units]] (SI) to make the metre defined as the distance travelled in a vacuum by light in 1&nbsp;/&nbsp;{{val|299792458}} second. This replaced the previous definition, valid between 1960 and 1983, which was that the metre equalled a certain number of wavelengths of a certain emission line of krypton-86. (The reason for the change was an improved method of measuring the speed of light.) The speed of light could then be expressed exactly as ''c''<sub>0</sub> = {{val|299792458|u=m/s}}, a standard also adopted by the [[International Earth Rotation and Reference Systems Service|IERS]] numerical standards.<ref name=IERS>{{cite report |title=Table 1.1: IERS numerical standards |work=IERS technical note no. 36: General definitions and numerical standards |editor=Gérard Petit |editor2=Brian Luzum |url=http://tai.bipm.org/iers/conv2010/chapter1/tn36_c1.pdf |publisher=[[International Earth Rotation and Reference Systems Service]] |date=2010}} For complete document see {{cite report |title=IERS Conventions (2010): IERS technical note no. 36 |editor=Gérard Petit |editor2=Brian Luzum |isbn=978-3-89888-989-6 |url=http://www.iers.org/nn_11216/IERS/EN/Publications/TechnicalNotes/tn36.html |publisher=International Earth Rotation and Reference Systems Service |date=2010}}</ref> From this definition and the 2009 IAU standard, the time for light to traverse an astronomical unit is found to be ''τ''<sub>A</sub> = {{val|499.0047838061|0.00000001|u=seconds}}, which is slightly more than 8&nbsp;minutes 19&nbsp;seconds. By multiplication, the best IAU 2009 estimate was ''A''&nbsp;= ''c''<sub>0</sub>''τ''<sub>A</sub>&nbsp;= {{val|149597870700|3|u=metres}},<ref name=Captaine>{{cite report |last1=Capitaine |first1=Nicole |last2=Klioner |first2=Sergei |last3=McCarthy |first3=Dennis | author3-link = Dennis McCarthy (scientist) |title=IAU Joint Discussion&nbsp;7: Space-time reference systems for future research at IAU General Assembly – The re-definition of the astronomical unit of length: Reasons and consequences |volume=7 |pages=40 |place=Beijing, China |date=2012 |url=http://referencesystems.info/uploads/3/0/3/0/3030024/jd7_5-06.pdf |access-date=16 May 2013 |bibcode=2012IAUJD...7E..40C}}</ref> based on a comparison of Jet Propulsion Laboratory and [[Russian Academy of Sciences|IAA–RAS]] ephemerides.<ref name="IAU">{{cite report |title=IAU WG on NSFA current best estimates |url=http://maia.usno.navy.mil/NSFA/CBE.html |access-date=25 September 2009 |url-status=dead |archive-url=https://web.archive.org/web/20091208011235/http://maia.usno.navy.mil/NSFA/CBE.html |archive-date=8 December 2009 }}</ref><ref name="Pitjeva09">{{cite journal |last1=Pitjeva |first1=E.V. |author-link1=Elena V. Pitjeva |last2=Standish |first2=E.M. |author-link2=E. Myles Standish |date=2009 |title=Proposals for the masses of the three largest asteroids, the Moon-Earth mass ratio and the Astronomical Unit |journal=[[Celestial Mechanics and Dynamical Astronomy]] |volume=103 |issue=4 |pages=365–72 |doi=10.1007/s10569-009-9203-8 |bibcode=2009CeMDA.103..365P |s2cid=121374703 |url=https://zenodo.org/record/1000691 }}</ref><ref>{{cite news |url=http://www.astronomy2009.com.br/10.pdf |newspaper=Estrella d'Alva |date=14 August 2009 |page=1 |title=The final session of the [IAU] General Assembly |url-status=dead |archive-url=https://web.archive.org/web/20110706151452/http://www.astronomy2009.com.br/10.pdf |archive-date=6 July 2011 }}</ref>


== Види још ==
== Види још ==
Ред 8: Ред 40:
* [[Светлосна година]]
* [[Светлосна година]]


== Референце ==
{{клица-космос}}
{{Reflist|25em}}

== Литература ==
{{Refbegin|}}
* {{cite journal |last1=Williams |first1=D. |last2=Davies |first2=R. D. |date=1968 |title=A radio method for determining the astronomical unit |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=140 |issue=4 |page=537 |bibcode=1968MNRAS.140..537W |doi=10.1093/mnras/140.4.537 |ref=none|doi-access=free }}
{{Refend}}

== Спољашње везе ==
{{Commons category|Astronomical unit}}
* [https://www.iau.org/public_press/themes/measuring/ The IAU and astronomical units]
* [https://web.archive.org/web/20070216041250/http://www.iau.org/Units.234.0.html Recommendations concerning Units] (HTML version of the IAU Style Manual)
* [http://www.sil.si.edu/exhibitions/chasing-venus/intro.htm Chasing Venus, Observing the Transits of Venus]
* [http://www.transitofvenus.org/ Transit of Venus]

{{СИ јединице}}
{{СИ јединице}}
{{нормативна контрола}}
{{нормативна контрола}}

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{{DEFAULTSORT:Астрономска јединица}}


[[Категорија:Астрономија|АУ]]
[[Категорија:Астрономија|АУ]]

Верзија на датум 8. јануар 2022. у 08:33

Астрономска јединица
Сива линија означава удаљеност Земља-Сунце, која је у просеку око 1 астрономске јединице.
Информације о јединици
СистемАстрономски систем јединица
(Прихваћено за употребу са СИ)
Јединицадужина
Симболај или AU или АЈ 
Јединична претварања
1 ај или AU или АЈ у ...... је једнак са ...
   метеричке (СИ) јединице   1,495978707×1011 m
   империјалне & УС јединице   9,2956×107 mi
   астрономске јединице   4,8481×10−6 pc
   1,5813×10−5 ly

Астрономска јединица (АЈ) (енгл. Astronomical unit (AU); симбол: au или ua)[1][2][3] мера је за удаљеност једнака просечној удаљености Земље од Сунца. Данас прихваћена мера за АЈ је 149.597.870.691 метара (приближно 149.600.000 km).[4] Ово растојање добија се једноставним рачуном узимајући у обзир да нам је паралакса Сунца позната (тј. можемо је измерити) и износи око 8,794145 лучних секунди. Користи се често у астрономији за међупланетска растојања, тј. у оквиру Сунчевог система или других планетарних система. За међузвездана растојања користе се веће јединице, светлосна година и парсек.[5]

Историја употребе симбола

A variety of unit symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the International Astronomical Union (IAU) had used the symbol A to denote a length equal to the astronomical unit.[6] In the astronomical literature, the symbol AU was (and remains) common. In 2006, the International Bureau of Weights and Measures (BIPM) had recommended ua as the symbol for the unit.[7] In the non-normative Annex C to ISO 80000-3:2006 (now withdrawn), the symbol of the astronomical unit was "ua".

In 2012, the IAU, noting "that various symbols are presently in use for the astronomical unit", recommended the use of the symbol "au".[1] The scientific journals published by the American Astronomical Society and the Royal Astronomical Society subsequently adopted this symbol.[3][8] In the 2014 revision and 2019 edition of the SI Brochure, the BIPM used the unit symbol "au".[9][10] ISO 80000-3:2019, which replaces ISO 80000-3:2006, does not mention the astronomical unit.[11][12]

Развој дефиниције јединице

Earth's orbit around the Sun is an ellipse. The semi-major axis of this elliptic orbit is defined to be half of the straight line segment that joins the perihelion and aphelion. The centre of the Sun lies on this straight line segment, but not at its midpoint. Because ellipses are well-understood shapes, measuring the points of its extremes defined the exact shape mathematically, and made possible calculations for the entire orbit as well as predictions based on observation. In addition, it mapped out exactly the largest straight-line distance that Earth traverses over the course of a year, defining times and places for observing the largest parallax (apparent shifts of position) in nearby stars. Knowing Earth's shift and a star's shift enabled the star's distance to be calculated. But all measurements are subject to some degree of error or uncertainty, and the uncertainties in the length of the astronomical unit only increased uncertainties in the stellar distances. Improvements in precision have always been a key to improving astronomical understanding. Throughout the twentieth century, measurements became increasingly precise and sophisticated, and ever more dependent on accurate observation of the effects described by Einstein's theory of relativity and upon the mathematical tools it used.

Improving measurements were continually checked and cross-checked by means of improved understanding of the laws of celestial mechanics, which govern the motions of objects in space. The expected positions and distances of objects at an established time are calculated (in au) from these laws, and assembled into a collection of data called an ephemeris. NASA's Jet Propulsion Laboratory HORIZONS System provides one of several ephemeris computation services.[13]

In 1976, to establish an even precise measure for the astronomical unit, the IAU formally adopted a new definition. Although directly based on the then-best available observational measurements, the definition was recast in terms of the then-best mathematical derivations from celestial mechanics and planetary ephemerides. It stated that "the astronomical unit of length is that length (A) for which the Gaussian gravitational constant (k) takes the value 0,01720209895 when the units of measurement are the astronomical units of length, mass and time".[6][14][15] Equivalently, by this definition, one au is "the radius of an unperturbed circular Newtonian orbit about the sun of a particle having infinitesimal mass, moving with an angular frequency of 0,01720209895 radians per day";[16] or alternatively that length for which the heliocentric gravitational constant (the product GM☉) is equal to (0,01720209895)2 au3/d2, when the length is used to describe the positions of objects in the Solar System.

Subsequent explorations of the Solar System by space probes made it possible to obtain precise measurements of the relative positions of the inner planets and other objects by means of radar and telemetry. As with all radar measurements, these rely on measuring the time taken for photons to be reflected from an object. Because all photons move at the speed of light in vacuum, a fundamental constant of the universe, the distance of an object from the probe is calculated as the product of the speed of light and the measured time. However, for precision the calculations require adjustment for things such as the motions of the probe and object while the photons are transiting. In addition, the measurement of the time itself must be translated to a standard scale that accounts for relativistic time dilation. Comparison of the ephemeris positions with time measurements expressed in Barycentric Dynamical Time (TDB) leads to a value for the speed of light in astronomical units per day (of 86400 s). By 2009, the IAU had updated its standard measures to reflect improvements, and calculated the speed of light at 173,1446326847(69) au/d (TDB).[17]

In 1983, the CIPM modified the International System of Units (SI) to make the metre defined as the distance travelled in a vacuum by light in 1 / 299792458 second. This replaced the previous definition, valid between 1960 and 1983, which was that the metre equalled a certain number of wavelengths of a certain emission line of krypton-86. (The reason for the change was an improved method of measuring the speed of light.) The speed of light could then be expressed exactly as c0 = 299792458 m/s, a standard also adopted by the IERS numerical standards.[18] From this definition and the 2009 IAU standard, the time for light to traverse an astronomical unit is found to be τA = 499,0047838061±0,00000001 s, which is slightly more than 8 minutes 19 seconds. By multiplication, the best IAU 2009 estimate was A = c0τA = 149597870700±3 m,[19] based on a comparison of Jet Propulsion Laboratory and IAA–RAS ephemerides.[20][21][22]

Види још

Референце

  1. ^ а б On the re-definition of the astronomical unit of length (PDF). XXVIII General Assembly of International Astronomical Union. Beijing, China: International Astronomical Union. 31. 8. 2012. Resolution B2. „... recommends ... 5. that the unique symbol "au" be used for the astronomical unit.” 
  2. ^ „Monthly Notices of the Royal Astronomical Society: Instructions for Authors”. Oxford Journals. Архивирано из оригинала 22. 10. 2012. г. Приступљено 20. 3. 2015. „The units of length/distance are Å, nm, μm, mm, cm, m, km, au, light-year, pc.” 
  3. ^ а б „Manuscript Preparation: AJ & ApJ Author Instructions”. American Astronomical Society. Архивирано из оригинала 21. 2. 2016. г. Приступљено 29. 10. 2016. „Use standard abbreviations for ... natural units (e.g., au, pc, cm).” 
  4. ^ On the re-definition of the astronomical unit of length (PDF). XXVIII General Assembly of International Astronomical Union. Beijing: International Astronomical Union. 31. 8. 2012. Resolution B2. „... recommends [adopted] that the astronomical unit be re-defined to be a conventional unit of length equal to exactly 149,597,870,700 metres, in agreement with the value adopted in IAU 2009 Resolution B2” 
  5. ^ Luque, B.; Ballesteros, F.J. (2019). „Title: To the Sun and beyond”. Nature Physics. 15: 1302. doi:10.1038/s41567-019-0685-3 Слободан приступ. 
  6. ^ а б Commission 4: Ephemerides/Ephémérides (1976). item 12: Unit distance (PDF). XVIth General Assembly of the International Astronomical Union. IAU (1976) System of Astronomical Constants. Grenoble, FR. Commission 4, part III, Recommendation 1, item 12. 
  7. ^ Bureau International des Poids et Mesures (2006), The International System of Units (SI) (PDF) (8th изд.), Organisation Intergouvernementale de la Convention du Mètre, стр. 126 
  8. ^ „Instructions to Authors”. Monthly Notices of the Royal Astronomical Society. Oxford University Press. Приступљено 5. 11. 2020. „The units of length/distance are Å, nm, µm, mm, cm, m, km, au, light-year, pc.” 
  9. ^ „The International System of Units (SI)”. SI Brochure (8th изд.). BIPM. 2014 [2006]. Приступљено 3. 1. 2015. 
  10. ^ „The International System of Units (SI)” (PDF). SI Brochure (9th изд.). BIPM. 2019. стр. 145. Приступљено 1. 7. 2019. 
  11. ^ „ISO 80000-3:2019”. International Organization for Standardization. Приступљено 2020-07-03. 
  12. ^ „Part 3: Space and time”. Quantities and units. International Organization for Standardization. ISO 80000-3:2019(en). Приступљено 2020-07-03. 
  13. ^ „HORIZONS System”. Solar system dynamics. NASA: Jet Propulsion Laboratory. 4. 1. 2005. Приступљено 16. 1. 2012. 
  14. ^ Hussmann, H.; Sohl, F.; Oberst, J. (2009). „§ 4.2.2.1.3: Astronomical units”. Ур.: Trümper, Joachim E. Astronomy, astrophysics, and cosmology – Volume VI/4B Solar System. Springer. стр. 4. ISBN 978-3-540-88054-7. 
  15. ^ Williams Gareth V. (1997). „Astronomical unit”. Ур.: Shirley, James H.; Fairbridge, Rhodes Whitmore. Encyclopedia of planetary sciences. Springer. стр. 48. ISBN 978-0-412-06951-2. 
  16. ^ International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th изд.), стр. 126, ISBN 92-822-2213-6 
  17. ^ „Selected Astronomical Constants” (PDF). The Astronomical Almanac Online. USNO–UKHO. 2009. стр. K6. Архивирано из оригинала (PDF) 26. 7. 2014. г. 
  18. ^ Gérard Petit; Brian Luzum, ур. (2010). Table 1.1: IERS numerical standards (PDF). IERS technical note no. 36: General definitions and numerical standards (Извештај). International Earth Rotation and Reference Systems Service.  For complete document see Gérard Petit; Brian Luzum, ур. (2010). IERS Conventions (2010): IERS technical note no. 36 (Извештај). International Earth Rotation and Reference Systems Service. ISBN 978-3-89888-989-6. 
  19. ^ Capitaine, Nicole; Klioner, Sergei; McCarthy, Dennis (2012). IAU Joint Discussion 7: Space-time reference systems for future research at IAU General Assembly – The re-definition of the astronomical unit of length: Reasons and consequences (PDF) (Извештај). 7. Beijing, China. стр. 40. Bibcode:2012IAUJD...7E..40C. Приступљено 16. 5. 2013. 
  20. ^ IAU WG on NSFA current best estimates (Извештај). Архивирано из оригинала 8. 12. 2009. г. Приступљено 25. 9. 2009. 
  21. ^ Pitjeva, E.V.; Standish, E.M. (2009). „Proposals for the masses of the three largest asteroids, the Moon-Earth mass ratio and the Astronomical Unit”. Celestial Mechanics and Dynamical Astronomy. 103 (4): 365—72. Bibcode:2009CeMDA.103..365P. S2CID 121374703. doi:10.1007/s10569-009-9203-8. 
  22. ^ „The final session of the [IAU] General Assembly” (PDF). Estrella d'Alva. 14. 8. 2009. стр. 1. Архивирано из оригинала (PDF) 6. 7. 2011. г. 

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