Editing Polar orbit

{{short description|Satellite orbit with high inclination}}
[[File:Polar orbit.ogv|thumb|200px|Polar orbit]]
A '''polar orbit''' is one in which a [[satellite]] [[pass (spaceflight)|pass]]es above or nearly above both [[Poles of astronomical bodies|poles]] of the body being [[orbit]]ed (usually a planet such as the [[Earth]], but possibly another body such as the [[Moon]] or [[Sun]]) on each revolution. It has an [[inclination]] of about 80–90 [[Degree (angle)|degree]]s to the body's [[equator]].<ref name="esa">{{cite web |url = http://www.esa.int/Enabling_Support/Space_Transportation/Types_of_orbits |title=ESA - Types of Orbits |date=2020-03-30 |access-date=2021-01-10}}</ref>

Launching [[satellite]]s into polar orbit requires a larger [[launch vehicle]] to launch a given payload to a given altitude than for a [[near-equatorial orbit]] at the same altitude, because it cannot take advantage of the [[Earth's rotation]]al [[velocity]]. Depending on the location of the [[Spaceport|launch site]] and the [[Orbital_inclination|inclination]] of the polar orbit, the launch vehicle may lose up to 460 m/s of [[Delta-v]], approximately 5% of the Delta-v required to attain [[Low Earth orbit]].

==Usage==
Polar orbits are used for [[Earth observation satellite|Earth-mapping]], [[reconnaissance satellite]]s, as well as for some [[weather satellite]]s.<ref>Science Focus 2nd Edition 2, pg. 297</ref>
The [[Iridium satellite constellation]] uses a polar orbit to provide telecommunications services.

{{anchor|nearPolarOrbit}}Near-polar orbiting satellites commonly choose a [[sun-synchronous orbit]], where each successive orbital [[pass (spaceflight)|pass]] occurs at the same local time of day. For some applications, such as [[remote sensing]],  it is important that ''changes'' over time are not aliased by changes in local time. Keeping the same local time on a given pass requires that the [[frequency|time period]] of the orbit be kept as short, which requires a low orbit. However, very low orbits rapidly [[orbital decay|decay]] due to [[drag (physics)|drag]] from the atmosphere. Commonly used [[altitude]]s are between 700 and 800&nbsp;km, producing an [[orbital period]] of about 100 minutes.<ref name="phy6">{{cite web |url=http://www.phy6.org/Education/wlopolar.html |title=Polar Orbiting Satellites |first=David P. |last=Stern |date=2001-11-25 |access-date=2009-01-21}}</ref> The half-orbit on the Sun side then takes only 50 minutes, during which local time of day does not vary greatly.

{{anchor|precessingSV}}To retain a Sun-synchronous orbit as the [[Earth's orbit|Earth revolves]] around the Sun during the year, the orbit must [[Nodal precession|precess]] about the Earth at the same rate (which is not possible if the satellite passes directly over the pole).
Because of Earth's [[equatorial bulge]], an orbit [[orbital inclination|inclined]] at a slight angle is subject to a [[torque]], which causes [[precession]]. An angle of about 8° from the pole produces the desired precession in a 100-minute orbit.<ref name="phy6" />

== Exoplanets ==
[[File:2M1510 (AB) b, a planet in a perpendicular orbit around two brown dwarfs (eso2508a).jpg|thumb|right|Orbit of the planet (orange orbit) around the brown dwarf binary 2M1510AB (blue orbits).]]
A misalignment between host star rotation plane and orbital plane of the planet is called [[obliquity]] and is usually measured with the [[Rossiter–McLaughlin effect|Rossiter-McLaughlin effect]]. Around 10% of exoplanets have a misalignment between 80 and 125°.<ref>{{Cite journal |last1=Albrecht |first1=Simon H. |last2=Marcussen |first2=Marcus L. |last3=Winn |first3=Joshua N. |last4=Dawson |first4=Rebekah I. |last5=Knudstrup |first5=Emil |date=July 2021 |title=A Preponderance of Perpendicular Planets |journal=The Astrophysical Journal |language=en |volume=916 |issue=1 |pages=L1 |arxiv=2105.09327 |bibcode=2021ApJ...916L...1A |doi=10.3847/2041-8213/ac0f03 |doi-access=free |issn=0004-637X}}</ref> About half of these are warm [[Neptune|Neptune]] sized or super-Neptune sized planets.<ref name=":0">{{Cite journal |last1=Louden |first1=Emma M. |last2=Millholland |first2=Sarah C. |date=October 2024 |title=Polar Neptunes Are Stable to Tides |journal=The Astrophysical Journal |language=en |volume=974 |issue=2 |pages=304 |arxiv=2409.03679 |bibcode=2024ApJ...974..304L |doi=10.3847/1538-4357/ad74ff |doi-access=free |issn=0004-637X}}</ref> Examples of exoplanets with nearly polar orbits are [[GJ 3470 b|GJ 3470b]], [[TOI-858Bb]], [[WASP-178b]],<ref name=":1">{{Cite journal |last1=Czekala |first1=Ian |last2=Chiang |first2=Eugene |last3=Andrews |first3=Sean M. |last4=Jensen |first4=Eric L. N. |last5=Torres |first5=Guillermo |last6=Wilner |first6=David J. |last7=Stassun |first7=Keivan G. |last8=Macintosh |first8=Bruce |date=September 2019 |title=The Degree of Alignment between Circumbinary Disks and Their Binary Hosts |journal=The Astrophysical Journal |language=en |volume=883 |issue=1 |pages=22 |arxiv=1906.03269 |bibcode=2019ApJ...883...22C |doi=10.3847/1538-4357/ab287b |doi-access=free |issn=0004-637X}}</ref> [[HD 3167|HD 3167c+d]],<ref>{{Cite journal |last1=Dalal |first1=S. |last2=Hébrard |first2=G. |last3=Lecavelier des Étangs |first3=A. |last4=Petit |first4=A. C. |last5=Bourrier |first5=V. |last6=Laskar |first6=J. |last7=König |first7=P.-C. |last8=Correia |first8=A. C. M. |date=November 2019 |title=Nearly polar orbit of the sub-Neptune HD 3167 c. Constraints on the dynamical history of a multi-planet system |url=https://ui.adsabs.harvard.edu/abs/2019A&A...631A..28D/abstract |journal=Astronomy and Astrophysics |language=en |volume=631 |pages=A28 |arxiv=1906.11013 |bibcode=2019A&A...631A..28D |doi=10.1051/0004-6361/201935944 |issn=0004-6361}}</ref> [[TOI-640 b|TOI-640b]],<ref>{{Cite journal |last1=Knudstrup |first1=Emil |last2=Albrecht |first2=Simon H. |last3=Gandolfi |first3=Davide |last4=Marcussen |first4=Marcus L. |last5=Goffo |first5=Elisa |last6=Serrano |first6=Luisa M. |last7=Dai |first7=Fei |last8=Redfield |first8=Seth |last9=Hirano |first9=Teruyuki |last10=Csizmadia |first10=Szilárd |last11=Cochran |first11=William D. |last12=Deeg |first12=Hans J. |last13=Fridlund |first13=Malcolm |last14=Lam |first14=Kristine W. F. |last15=Livingston |first15=John H. |date=March 2023 |title=A puffy polar planet. The low density, hot Jupiter TOI-640 b is on a polar orbit |url=https://ui.adsabs.harvard.edu/abs/2023A&A...671A.164K/abstract |journal=Astronomy and Astrophysics |language=en |volume=671 |pages=A164 |arxiv=2302.01702 |bibcode=2023A&A...671A.164K |doi=10.1051/0004-6361/202245301 |issn=0004-6361}}</ref> [[MASCARA-1b|MASCARA-1 b]],<ref>{{Cite journal |last1=Hooton |first1=M. J. |last2=Hoyer |first2=S. |last3=Kitzmann |first3=D. |last4=Morris |first4=B. M. |last5=Smith |first5=A. M. S. |last6=Collier Cameron |first6=A. |last7=Futyan |first7=D. |last8=Maxted |first8=P. F. L. |last9=Queloz |first9=D. |last10=Demory |first10=B.-O. |last11=Heng |first11=K. |last12=Lendl |first12=M. |last13=Cabrera |first13=J. |last14=Csizmadia |first14=Sz |last15=Deline |first15=A. |date=February 2022 |title=Spi-OPS: Spitzer and CHEOPS confirm the near-polar orbit of MASCARA-1 b and reveal a hint of dayside reflection |url=https://ui.adsabs.harvard.edu/abs/2022A&A...658A..75H/abstract |journal=Astronomy and Astrophysics |language=en |volume=658 |pages=A75 |arxiv=2109.05031 |bibcode=2022A&A...658A..75H |doi=10.1051/0004-6361/202141645 |issn=0004-6361}}</ref> and [[Gliese 436 b|GJ 436b]].<ref>{{Cite journal |last1=Bourrier |first1=V. |last2=Zapatero Osorio |first2=M. R. |last3=Allart |first3=R. |last4=Attia |first4=M. |last5=Cretignier |first5=M. |last6=Dumusque |first6=X. |last7=Lovis |first7=C. |last8=Adibekyan |first8=V. |last9=Borsa |first9=F. |last10=Figueira |first10=P. |last11=González Hernández |first11=J. I. |last12=Mehner |first12=A. |last13=Santos |first13=N. C. |last14=Schmidt |first14=T. |last15=Seidel |first15=J. V. |date=July 2022 |title=The polar orbit of the warm Neptune GJ 436b seen with VLT/ESPRESSO |url=https://ui.adsabs.harvard.edu/abs/2022A&A...663A.160B/abstract |journal=Astronomy and Astrophysics |language=en |volume=663 |pages=A160 |arxiv=2203.06109 |bibcode=2022A&A...663A.160B |doi=10.1051/0004-6361/202142559 |issn=0004-6361}}</ref>

One explanation describes the misalignment of a [[circumbinary disk]] that forms the planets. When the central binary merges into a single star, the disk and any planets that have formed remain in a polar orbit.<ref>{{Cite journal |last1=Chen |first1=Cheng |last2=Baronett |first2=Stanley A. |last3=Nixon |first3=C. J. |last4=Martin |first4=Rebecca G. |date=September 2024 |title=On the origin of polar planets around single stars |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=533 |issue=1 |pages=L37–L42 |arxiv=2406.16169 |bibcode=2024MNRAS.533L..37C |doi=10.1093/mnrasl/slae058 |doi-access=free |issn=0035-8711}}</ref> A study has shown that circumbinary disks are aligned with binaries that have a short orbital period of less than 20 days. Circumbinary disks around binaries with an orbital period of more than 30 days showed a wide range of alignments, including polar disks.<ref name=":1" /> The other explanation describes how a Neptune-sized planet might get into a polar orbit at the end of the planet formation. This happens due to a [[resonance]] with a [[protoplanetary disk]] in a system with an additional outer planet.<ref>{{Cite journal |last1=Petrovich |first1=Cristobal |last2=Muñoz |first2=Diego J. |last3=Kratter |first3=Kaitlin M. |last4=Malhotra |first4=Renu |date=October 2020 |title=A Disk-driven Resonance as the Origin of High Inclinations of Close-in Planets |journal=The Astrophysical Journal |language=en |volume=902 |issue=1 |pages=L5 |arxiv=2008.08587 |bibcode=2020ApJ...902L...5P |doi=10.3847/2041-8213/abb952 |doi-access=free |issn=0004-637X}}</ref><ref name=":0" />

In April 2025 astronomers using [[European Southern Observatory|ESO]]'s UVES instrument on the [[Very Large Telescope]] announced strong evidence for a [[circumbinary planet]] orbiting the brown dwarf pair [[2M1510]]AB. The planet is called 2M1510(AB)b, or just 2M1510b. The orbit of the planet is unusual as it is a [[polar orbit]] around a binary system, the first such case that was discovered. The discovery was made with the help of [[radial velocity]] measurements that showed [[Retrograde and prograde motion|retrograde]] [[apsidal precession]] of the brown dwarf pair, which could not be explained by the outer companion.

==See also==
*[[List of orbits]]
*[[Molniya orbit]]
*[[Tundra orbit]]
*[[Vandenberg Air Force Base]], a major United States launch location for polar orbits

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20120204054322/http://www.braeunig.us/space/orbmech.htm Orbital Mechanics] (Rocket and Space Technology) 	

{{orbits}}

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