View source for Thebe (moon)

{{Short description|Moon of Jupiter}}
{{Infobox planet
| name = Thebe
| image = thebe.jpg
| caption = Image of Thebe taken by the ''Galileo'' spacecraft on 4 January 2000. The large crater near the center is [[Zethus (crater)|Zethus]]
| discoverer = [[Stephen P. Synnott]] / ''Voyager 1''
| discovered = 5 March 1979
| pronounced = {{IPAc-en|ˈ|θ|iː|b|iː}}<ref>Noah Webster (1884) ''A Practical Dictionary of the English Language''</ref> 
| named_after = [[List of mythological figures named Thebe|Θήβη]] ''Thēbē''
| adjectives = Thebean {{IPAc-en|θ|iː|ˈ|b|iː|ə|n}}<ref>The adjectives "Theban" and sometimes "Thebean" (with stress on the first syllable) refer to the city of [[Thebes, Greece]].</ref>
| mean_orbit_radius = {{val|221889.0|0.6|u=km}} ({{Jupiter radius|3.11}}){{sfn|Cooper Murray et al.|2006}}
| periapsis = {{val|218000|u=km}}{{efn|Calculated as a×(1&nbsp;−&nbsp;e), where a is semimajor axis and e is eccentricity.}}
| apoapsis = {{val|226000|u=km}}{{efn|Calculated as a×(1&nbsp;+&nbsp;e), where a is semimajor axis and e is eccentricity.}}
| eccentricity = {{val|0.0175|0.0004}}{{sfn|Cooper Murray et al.|2006}}
| period = {{val|0.674536|0.000001|u=d}} (16 h 11.3 min){{sfn|Cooper Murray et al.|2006}}
| avg_speed = 23.92 km/s (calculated)
| inclination = {{val|1.076|0.003|u=°}} (to Jupiter's equator){{sfn|Cooper Murray et al.|2006}}
| satellite_of = [[Jupiter]]
| mean_radius = {{val|49.3|2.0|u=km}}{{sfn|Thomas Burns et al.|1998}}
| dimensions = 116&thinsp;×&thinsp;98&thinsp;×&thinsp;84 km{{sfn|Thomas Burns et al.|1998}}
| volume = {{val|p=≈&thinsp;|500000|u=km<sup>3</sup>}}
| mass = 
| density = 
| surface_grav = {{val|0.04|u=m/s<sup>2</sup>}} (0.004 ''g''){{sfn|Thomas Burns et al.|1998}}{{efn|The estimate from [[#{{sfnRef|Thomas Burns et al.|1998}}|Thomas, 1998]] was divided by 1.5 to account for the difference in assumed densities.}}
| escape_velocity = 20–30m/s{{sfn|Burns Simonelli et al.|2004}}{{efn|The estimate from [[#{{sfnRef|Burns Simonelli et al.|2004}}|Burns, 2004]] was divided by 1.5 to account for the difference in assumed densities.}}
| rotation = [[synchronous rotation|synchronous]]
| axial_tilt = zero
| albedo = {{val|0.047|0.003}}{{sfn|Simonelli Rossier et al.|2000}}
| single_temperature = ≈&thinsp;124 K
}}

'''Thebe''' ({{IPAc-en|ˈ|θ|iː|b|iː}}), also known as '''{{nowrap|Jupiter XIV}}''', is the fourth of [[Moons of Jupiter|Jupiter's moons]] by distance from the [[planet]]. It was discovered by [[Stephen P. Synnott]] in images from the ''[[Voyager 1]]'' space probe taken on March 5, 1979, while making its flyby of [[Jupiter]].{{sfn|Synnott|1980}} In 1983, it was officially named after the [[Greek mythology|mythological]] [[nymph]] [[List of mythological figures named Thebe|Thebe]].{{sfn|IAUC 3872}}

The second largest of the [[inner satellites of Jupiter]], Thebe orbits within the outer edge of the [[Rings of Jupiter#Thebe gossamer ring|Thebe gossamer ring]] that is formed from dust ejected from its surface.{{sfn|Burns Simonelli et al.|2004}} It is irregularly shaped and reddish in colour, and is thought like [[Amalthea (moon)|Amalthea]] to consist of porous water ice with unknown amounts of other materials. Its surface features include large craters and high mountains—some of them are comparable to the size of the moon itself.{{sfn|Thomas Burns et al.|1998}}

Thebe was photographed in 1979 by the [[Voyager program|''Voyager 1'' and ''2'']] spacecraft, and later, in more detail, by the [[Galileo spacecraft|''Galileo'' orbiter]] in the 1990s.{{sfn|Thomas Burns et al.|1998}}

== Discovery and observations ==

Thebe was discovered by [[Stephen P. Synnott]] in images from the ''[[Voyager 1]]'' space probe taken on March 5, 1979, and was initially given the provisional designation '''{{nowrap|S/1979 J 2}}'''.{{sfn|Synnott|1980}}{{sfn|IAUC 3470}} In 1983 it was officially named after the mythological [[nymph]] [[List of mythological figures named Thebe|Thebe]] who was a lover of [[Zeus]]—the Greek equivalent of Jupiter.{{sfn|IAUC 3872}}

After its discovery by ''Voyager 1'', Thebe was photographed by the ''[[Voyager 2]]'' space probe in 1979.{{sfn|Burns Simonelli et al.|2004}} However, before the [[Galileo spacecraft|''Galileo'' spacecraft]] arrived at Jupiter, knowledge about it was extremely limited. ''Galileo'' imaged almost all of the surface of Thebe and helped clarify its composition.{{sfn|Thomas Burns et al.|1998}}

== Orbit ==

Thebe is the outermost of the [[inner satellites of Jupiter|inner Jovian moons]], and orbits Jupiter at a distance of about 222,000&nbsp;km (3.11 Jupiter radii). Its orbit has an [[orbital eccentricity|eccentricity]] of 0.018, and an [[inclination]] of 1.08° relative to the equator of Jupiter.{{sfn|Cooper Murray et al.|2006}} These values are unusually high for an [[inner satellite]] and can be explained by the past influence of the innermost [[Galilean satellite]], [[Io (moon)|Io]];{{sfn|Burns Simonelli et al.|2004}} in the past, several [[orbital resonance|mean-motion resonances]] with [[Io (moon)|Io]] would have passed through Thebe's orbit as Io gradually receded from Jupiter, and these excited Thebe's orbit.{{sfn|Burns Simonelli et al.|2004}}

The orbit of Thebe lies near the outer edge of the [[Rings of Jupiter#Thebe gossamer ring|Thebe gossamer ring]], which is composed of the dust ejected from the satellite. After ejection, the dust drifts in the direction of the planet under the action of [[Poynting–Robertson drag]], forming a ring inward of the moon.{{sfn|Burns Showalter et al.|1999}}

== Physical characteristics ==
[[File:Thebe - January 4 2000 (26781645690).jpg|thumb|left|Thebe and Zethus crater imaged by the ''Galileo'' spacecraft in January 2000]]

Thebe is irregularly shaped, with the closest [[ellipsoid]]al approximation being 116×98×84&nbsp;km. Its surface area is probably between 31,000 and 59,000 (~45,000) km<sup>2</sup>. Its bulk density and mass are not known, but assuming that its mean [[density]] is like that of Amalthea (around 0.86&nbsp;g/cm<sup>3</sup>),{{sfn|Thomas Burns et al.|1998}} its mass can be estimated at 4.3{{E-sp|17}}&nbsp;kg.

Similarly to all inner satellites of Jupiter, Thebe [[synchronous rotation|rotates synchronously]] with its orbital motion, thus keeping one face always looking toward the planet. Its orientation is such that the long axis always points to Jupiter.{{sfn|Burns Simonelli et al.|2004}} At the surface points closest to and furthest from Jupiter, the surface is thought to be near the edge of the [[Roche limit]], where Thebe's gravity is only slightly larger than the [[centrifugal force]].{{sfn|Burns Simonelli et al.|2004}} As a result, the [[escape velocity]] in these two points is very small, thus allowing dust to escape easily after meteorite impacts, and ejecting it into the Thebe gossamer ring.{{sfn|Burns Simonelli et al.|2004}}

[[Zethus (crater)|Zethus]] {{IPAc-en|ˈ|z|iː|θ|ə|s}} is the largest (diameter about 40&nbsp;km) crater on and the only named surface feature of [[Jupiter]]'s moon Thebe. There are several bright spots at the [[Rim (craters)|rim]] of this crater.{{sfn|Thomas Burns et al.|1998}} It is located on the far side of Thebe, facing away from Jupiter. It was discovered by the [[Galileo (spacecraft)|''Galileo'']] spacecraft. It is named for [[Amphion and Zethus|Zethus]] (Ζῆθος), the husband of the nymph [[List of mythological figures named Thebe|Thebe]] in [[Greek mythology]].<ref name="USGS">{{cite web | url=https://planetarynames.wr.usgs.gov/Feature/6726;jsessionid=48811DDB28403E26694E8532F0E7609E?__fsk=1567792439 | title=Planetary Names: Crater, craters: Zethus on Thebe | publisher=United States Geological Survey | date=October 3, 2006 | access-date=August 7, 2015}}</ref>

The surface of Thebe is dark and appears to be reddish in color.{{sfn|Simonelli Rossier et al.|2000}} There is a substantial asymmetry between the leading and trailing [[Sphere|hemispheres]]: the leading hemisphere is 1.3&nbsp;times brighter than the trailing one. The asymmetry is probably caused by the higher velocity and frequency of [[impact crater|impacts]] on the leading hemisphere, which excavates a bright material (probably ice) from the interior of the moon.{{sfn|Simonelli Rossier et al.|2000}} The surface of Thebe is heavily cratered and it appears that there are at least three or four large [[impact crater]]s, each being roughly comparable in size to Thebe itself.{{sfn|Burns Simonelli et al.|2004}}

== References ==

'''Explanatory notes'''

{{notes}}

'''Citations'''

{{reflist|20em}}

'''Cited sources'''

* {{cite journal| doi = 10.1126/science.284.5417.1146| last1 = Burns| first1 = Joseph A.| last2 = Showalter| first2 = Mark R.| last3 = Hamilton| first3 = Douglas P.| last4 = Nicholson| first4 = Philip D.| last5 = de Pater| first5 = Imke|author-link5=Imke de Pater| last6 = Ockert-Bell| first6 = Maureen E.| last7 = Thomas| first7 = Peter C.| date = 14 May 1999| title = The Formation of Jupiter's Faint Rings| journal = Science| volume = 284| issue = 5417| pages = 1146–1150| pmid = 10325220| bibcode = 1999Sci...284.1146B| ref = {{sfnRef|Burns Showalter et al.|1999}}}}
* {{cite encyclopedia
  | last1 = Burns
  | first1 = Joseph A.
  | last2 = Simonelli
  | first2 = Damon P.
  | last3 = Showalter
  | first3 = Mark R.
  | last4 = Hamilton
  | first4 = Douglas P.
  | last5 = Porco
  | first5 = Carolyn C.
  | last6 = Throop
  | first6 = Henry
  | last7 = Esposito
  | first7 = Larry W.
  | date = 2004
  | pages = 241–262
  | title = Jupiter's Ring-Moon System
  | encyclopedia = Jupiter: The Planet, Satellites and Magnetosphere
  | publisher = Cambridge University Press
  | editor1-last = Bagenal
  | editor1-first = Fran
  | editor2-last = Dowling
  | editor2-first = Timothy E.
  | editor3-last = McKinnon
  | editor3-first = William B.
  | url = http://www.astro.umd.edu/~hamilton/research/preprints/BurSimSho03.pdf
  | bibcode = 2004jpsm.book..241B
  | isbn = 978-0-521-81808-7
  | ref = {{sfnRef|Burns Simonelli et al.|2004}}
  }}
* {{cite journal| doi = 10.1016/j.icarus.2005.11.007| last1 = Cooper | first1 = N. J.| last2 = Murray | first2 = C. D.| last3 = Porco | first3 = C. C.| last4 = Spitale | first4 = J. N.| date=March 2006 | title = Cassini ISS astrometric observations of the inner jovian satellites, Amalthea and Thebe| journal = Icarus| volume = 181| issue = 1| pages = 223–234| bibcode = 2006Icar..181..223C| ref = {{sfnRef|Cooper Murray et al.|2006}}}}
* {{cite journal
  | last = Marsden
  | first = Brian G.
  | date = April 28, 1980
  | title = Satellites of Jupiter
  | journal = IAU Circular
  | volume = 3470
  | url = http://www.cbat.eps.harvard.edu/iauc/03400/03470.html
  | access-date = 2012-03-28
  | ref = {{sfnRef|IAUC 3470}}
  }}
* {{cite journal
  | last = Marsden
  | first = Brian G.
  | date = September 30, 1983
  | title = Satellites of Jupiter and Saturn
  | journal = IAU Circular
  | volume = 3872
  | url = http://www.cbat.eps.harvard.edu/iauc/03800/03872.html
  | access-date = 2012-03-28
  | ref = {{sfnRef|IAUC 3872}}
  }}
* {{cite journal| doi = 10.1006/icar.2000.6474| last1 = Simonelli | first1 = D. P.| last2 = Rossier | first2 = L.| last3 = Thomas | first3 = P. C.| last4 = Veverka | first4 = J.| last5 = Burns | first5 = J. A.| last6 = Belton | first6 = M. J. S.| date=October 2000 | title = Leading/Trailing Albedo Asymmetries of Thebe, Amalthea, and Metis| journal = Icarus| volume = 147| issue = 2| pages = 353–365| bibcode = 2000Icar..147..353S| ref = {{sfnRef|Simonelli Rossier et al.|2000}}| doi-access = free}}
* {{cite journal| doi = 10.1126/science.210.4471.786| last = Synnott| first = S. P.| date = 14 November 1980| title = 1979J2: The Discovery of a Previously Unknown Jovian Satellite| journal = Science| volume = 210| issue = 4471| pages = 786–788| pmid = 17739548| bibcode = 1980Sci...210..786S}}
* {{cite journal| doi = 10.1006/icar.1998.5976| last1 = Thomas | first1 = P. C.| last2 = Burns | first2 = J. A.| last3 = Rossier | first3 = L.| last4 = Simonelli | first4 = D.| last5 = Veverka | first5 = J.| last6 = Chapman | first6 = C. R.| last7 = Klaasen | first7 = K.| last8 = Johnson | first8 = T. V.| last9 = Belton | first9 = M. J. S.| author10 = Galileo Solid State Imaging Team| date =September 1998| title = The Small Inner Satellites of Jupiter| journal = Icarus| volume = 135| issue = 1| pages = 360–371| bibcode = 1998Icar..135..360T| ref = {{sfnRef|Thomas Burns et al.|1998}}| doi-access = free}}
* {{cite web
  | author = [[USGS]]/[[IAU]]
  | title = Zethus on Thebe
  | publisher = USGS Astrogeology
  | work = Gazetteer of Planetary Nomenclature
  | url = https://planetarynames.wr.usgs.gov/Feature/6726
  | access-date = 2012-03-27
  | ref = {{sfnRef|USGS: Jupiter: Thebe: Zethus}}
  }}

== External links ==
* [https://web.archive.org/web/20070608072455/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Thebe Thebe Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [https://planetarynames.wr.usgs.gov/Page/THEBE/target Thebe nomenclature] from the [http://planetarynames.wr.usgs.gov USGS planetary nomenclature page]

{{Spoken Wikipedia|date=2025-06-09|En-Thebe_(moon)-article.ogg}}

{{Moons of Jupiter}}
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{{DEFAULTSORT:Thebe (Moon)}}
[[Category:Thebe (moon)| ]]
[[Category:Moons of Jupiter]]
[[Category:Astronomical objects discovered in 1979|19790305]]
[[Category:Discoveries by Stephen P. Synnott]]
[[Category:Moons with a prograde orbit]]