Sidereal year: Difference between revisions

Content deleted Content added

Inline

Latest revision as of 04:01, 8 April 2024

A sidereal year (/saɪˈdɪəri.əl/, US also /sɪ-/; from Latin sidus 'asterism, star'), also called a sidereal orbital period, is the time that Earth or another planetary body takes to orbit the Sun once with respect to the fixed stars.

Hence, for Earth, it is also the time taken for the Sun to return to the same position relative to Earth with respect to the fixed stars after apparently travelling once around the ecliptic.

It equals 365.256363004 ephemeris days for the J2000.0 epoch.^[1] The sidereal year differs from the solar year, "the period of time required for the ecliptic longitude of the Sun to increase 360 degrees",^[2] due to the precession of the equinoxes. The sidereal year is 20 min 24.5 s longer than the mean tropical year at J2000.0 (365.242 190 402 ephemeris days).^[1]

At present, the rate of axial precession corresponds to a period of 25,772 years,^[3] so sidereal year is longer than tropical year by 1,224.5 seconds (20 min 24.5 s, ~365.24219*86400/25772).

Before the discovery of the precession of the equinoxes by Hipparchus in the Hellenistic period, the difference between sidereal and tropical year was unknown to the Greeks.^[4] For naked-eye observation, the shift of the constellations relative to the equinoxes only becomes apparent over centuries or "ages", and pre-modern calendars such as Hesiod's Works and Days would give the times of the year for sowing, harvest, and so on by reference to the first visibility of stars, effectively using the sidereal year.^{[citation needed]} The Indian national calendar, based on the works of Maga Brahmins, as are the calendars of neighbouring countries, is traditionally reckoned by the Sun's entry into the sign of Aries and is also supposed to align with the spring equinox and have relevance to the harvesting and planting season and thus the tropical year.^{[citation needed]} However, as the entry into the constellation occurs 25 days later, according to the astronomical calculation of the sidereal year, this date marks the South and Southeast Asian solar New Year in other countries and cultures.^{[citation needed]}

Notes[edit]

^ ^a ^b IERS 2014.
^ AA 2016.
^ N. Capitaine et al. 2003, p. 581 expression 39
^ Stern, David P. (October 10, 2016). "Precession". NASA's Polar, Wind and Geotail Site. Retrieved April 25, 2022.

Works cited[edit]

"Glossary". Astronomical Almanac for the Year 2017. Washington, D.C., and London: United States Naval Observatory, HM Nautical Almanac Office. 2016. p. M19.
"Useful Constants". International Earth rotation and Reference systems Service (IERS). February 13, 2014. Retrieved February 29, 2020.

[FOOTNOTEIERS2014-1] IERS 2014.

[FOOTNOTEAA2016-2] AA 2016.

[3] N. Capitaine et al. 2003, p. 581 expression 39

[4] Stern, David P. (October 10, 2016). "Precession". NASA's Polar, Wind and Geotail Site. Retrieved April 25, 2022.

[1]

[2]

[3]

[4]

@@ Line 1: / Line 1: @@
+{{Use mdy dates|date=April 2022}}
 {{Short description|Time taken by the Earth to orbit the Sun once with respect to the fixed stars}}
-A '''sidereal year''' ({{IPAc-en|UK|s|aɪ|ˈ|d|ɪər|i|ə|l}}, {{IPAc-en|US|s|aɪ|ˈ|d|ɪr|i|ə|l|,_|s|ə|-}}; from Latin {{wikt-lang|la|sidus}} "asterism, star"; also '''sidereal orbital period''') is the time taken by the [[Earth]] or another [[planetary body]] to orbit the [[Sun]] once with respect to the [[fixed stars]].
+A '''sidereal year''' ({{IPAc-en|s|aɪ|ˈ|d|ɪər|i|.|əl}}, {{IPAc-en|USalso|s|ɪ|-}}; {{etymology|la|{{wikt-lang|la|sidus}}|asterism, star}}), also called a '''sidereal orbital period''', is the time that [[Earth]] or another [[planetary-mass object|planetary body]] takes to orbit the [[Sun]] once with respect to the [[fixed stars]].
-Hence, for the Earth, it farts is also the time taken for the Sun to return to the same position relative to the Earth with respect to the fixed stars after apparently travelling once around the [[ecliptic]].
-It equals {{Nowrap|365.256 363 004 [[Ephemeris day]]s}} for the [[Epoch (astronomy)#Julian years and J2000 |J2000.0]] epoch.{{Sfn|IERS|2014}} The sidereal year differs from the [[solar year]], "the period of time required for the ecliptic longitude of the Sun to increase 360 degrees",{{Sfn|AA|2016}} due to the [[Axial precession|precession of the equinoxes]].
+Hence, for Earth, it is also the time taken for the Sun to return to the same position relative to Earth with respect to the fixed stars after apparently travelling once around the [[ecliptic]].
+It equals {{Nowrap|{{val|365.256363004}} [[ephemeris day]]s}} for the [[Epoch (astronomy)#Julian years and J2000 |J2000.0]] epoch.{{Sfn|IERS|2014}} The sidereal year differs from the [[solar year]], "the period of time required for the ecliptic longitude of the Sun to increase 360 degrees",{{Sfn|AA|2016}} due to the [[Axial precession|precession of the equinoxes]].
 The sidereal year is 20&nbsp;min 24.5&nbsp;s longer than the mean tropical year at J2000.0 {{Nowrap|(365.242 190 402 ephemeris days)}}.{{Sfn|IERS|2014}}
-At present, the rate of [[axial precession]] corresponds to a period of 25,772 years, so sidereal year is longer than tropical year by 1,224.5 seconds (20 min 24.5 s, ~365.24219*86400/25772).
+At present, the rate of [[axial precession]] corresponds to a period of 25,772 years,<ref>[http://syrte.obspm.fr/iau2006/aa03_412_P03.pdf N. Capitaine ''et al.'' 2003], p. 581 expression 39</ref> so sidereal year is longer than [[tropical year]] by 1,224.5 seconds (20 min 24.5 s, ~365.24219*86400/25772).
+Before the discovery of the precession of the equinoxes by [[Hipparchus]] in the [[Hellenistic period]], the difference between
-Before the discovery of the precession of the equinoxes by [[Hipparchus]] in the [[Hellenistic period]], the difference between sidereal and tropical year was unknown.{{Citation needed|date=August 2020}} For naked-eye observation, the shift of the constellations relative to the equinoxes only becomes apparent over centuries or "[[Astrological age|ages]]", and pre-modern calendars such as [[Hesiod]]'s ''[[Works and Days]]'' would give the times of the year for sowing, harvest, and so on by reference to the first visibility of stars, effectively using the sidereal year.{{Citation needed|date=August 2020}} The [[South and Southeast Asian solar New Year]], based on Indic influences, is traditionally reckoned by the Sun's entry into [[Aries (constellation)|Aries]] and thus the sidereal year, but is also supposed to align with the spring equinox and have relevance to the harvesting and planting season and thus the tropical year.{{Citation needed|date=August 2020}} As these have grown apart, in some countries and cultures the date has been fixed according to the tropical year while in others the astronomical calculation and sidereal year is still used.{{Citation needed|date=August 2020}}
+sidereal and tropical year was unknown to the Greeks.<ref>{{Cite web| last = Stern| first = David P.| title = Precession| work = NASA's Polar, Wind and Geotail Site| accessdate = April 25, 2022| date = October 10, 2016| url = https://pwg.gsfc.nasa.gov/stargaze/Sprecess.htm}}</ref> For naked-eye observation, the shift of the constellations
+relative to the equinoxes only becomes apparent over centuries or "[[Astrological age|ages]]", and pre-modern calendars such as
+[[Hesiod]]'s ''[[Works and Days]]'' would give the times of the year for sowing, harvest, and so on by reference to the first visibility
+of stars, effectively using the sidereal year.{{Citation needed|date=August 2020}} The [[Indian national calendar]], based on the works of
+[[Maga Brahmin]]s, as are the calendars of neighbouring countries, is traditionally reckoned by the Sun's entry into the sign of
+[[Aries (astrology)|Aries]] and is also supposed to align with the spring equinox and have relevance to the harvesting and planting
+season and thus the tropical year.{{Citation needed|date=August 2020}} However, as the entry into the constellation occurs 25 days later,
+according to the astronomical calculation of the sidereal year, this date marks the  [[South and Southeast Asian solar New Year]] in
+other countries and cultures.{{Citation needed|date=August 2020}}
 == See also ==
@@ Line 27: / Line 38: @@
 == Works cited ==
-*{{Cite book | title=Astronomical Almanac for the Year 2017 | date=2016 | chapter=Glossary | page=M19 | publisher=[[United States Naval Observatory]], HM Nautical Almanac Office | location=Washington, D.C. and London | ref={{SfnRef|AA|2016}}}}
+*{{Cite book |title=Astronomical Almanac for the Year 2017 |date=2016 |chapter=Glossary |page=M19 |publisher=[[United States Naval Observatory]], HM Nautical Almanac Office |location=Washington, D.C., and London |ref={{SfnRef|AA|2016}}}}
 *{{Cite web | title=Useful Constants | access-date=February 29, 2020 | url=https://hpiers.obspm.fr/eop-pc/models/constants.html | date=February 13, 2014 | publisher=International Earth rotation and Reference systems Service (IERS) | ref={{SfnRef|IERS|2014}}}}

v t e Time measurement and standards
Chronometry Orders of magnitude Metrology
International standards	Coordinated Universal Time offset UT ΔでるたT DUT1 International Earth Rotation and Reference Systems Service ISO 31-1 ISO 8601 International Atomic Time 12-hour clock 24-hour clock Barycentric Coordinate Time Barycentric Dynamical Time Civil time Daylight saving time Geocentric Coordinate Time International Date Line IERS Reference Meridian Leap second Solar time Terrestrial Time Time zone 180th meridian
Obsolete standards	Ephemeris time Greenwich Mean Time Prime meridian
Time in physics	Absolute space and time Spacetime Chronon Continuous signal Coordinate time Cosmological decade Discrete time and continuous time Proper time Theory of relativity Time dilation Gravitational time dilation Time domain Time-translation symmetry T-symmetry
Horology	Clock Astrarium Atomic clock Complication History of timekeeping devices Hourglass Marine chronometer Marine sandglass Radio clock Watch stopwatch Water clock Sundial Dialing scales Equation of time History of sundials Sundial markup schema
Calendar	Gregorian Hebrew Hindu Holocene Islamic (lunar Hijri) Julian Solar Hijri Astronomical Dominical letter Epact Equinox Intercalation Julian day Leap year Lunar Lunisolar Solar Solstice Tropical year Weekday determination Weekday names
Archaeology and geology	Chronological dating Geologic time scale International Commission on Stratigraphy
Astronomical chronology	Galactic year Nuclear timescale Precession Sidereal time
Other units of time	Instant Flick Shake Jiffy Second Minute Moment Hour Day Week Fortnight Month Year Olympiad Lustrum Decade Century Saeculum Millennium
Related topics	Chronology Duration music Mental chronometry Decimal time Metric time System time Time metrology Time value of money Timekeeper

Latest revision as of 04:01, 8 April 2024

See also[edit]

Notes[edit]

Works cited[edit]