Editing Atlas (moon)

{{Short description|Moon of Saturn}}
{{Infobox planet
| name = Atlas
| mpc_name = Saturn XV
| alt_names = S/1980 S 28
| adjectives = Atlantean {{IPAc-en|æ|t|l|æ|n|ˈ|t|iː|ə|n}}<ref>{{OED|Atlantean}}</ref>
| pronounced = {{IPAc-en|ˈ|æ|t|l|ə|s}}
| named_after = [[Atlas (mythology)|Ἄτλας]] ''Ātlās''
| image = Atlas color PIA21449.png
| image_scale =
| caption = Color photo taken by ''[[Cassini–Huygens|Cassini]]'' on 12 April 2017
| discoverer = [[Richard Terrile|Terrile]], [[Voyager 1]]
| discovered = October, 1980
| orbit_ref = {{sfn|Spitale Jacobson et al.|2006}}
| epoch = December 31, 2003 ([[Julian day|JD]] {{val|2453005.5}})
| mean_orbit_radius = {{val|137670|10|u=km}}
| eccentricity = {{val|0.0012}}
| period = {{val|0.6016947883|u=d}}
| inclination = {{val|0.003|0.004|u=°}}
| satellite_of = [[Saturn]]
| group = Outer [[shepherd moon]] of the [[A Ring]]
| dimensions = {{val|40.8|x|35.4|x|18.6}}&nbsp;km<br/>(±&nbsp;{{val|0.2|x|0.4|x|0.6}}&nbsp;km){{sfn|Thomas & Helfenstein|2020}}{{rp|page=2}}
| mean_diameter = {{val|29.8|0.4|u=km}}{{sfn|Thomas & Helfenstein|2020}}{{rp|page=2}}
| volume = {{val|13950|50|u=km3}}{{sfn|Lainey et al.|2023}}{{rp|page=4}}
| mass = {{val|5.490|0.042|e=15|u=kg}}{{efn|Calculated from the standard gravitational parameter ''GM'' {{=}} {{val|3.664|0.028|e=-4|u=km<sup>3</sup>·s<sup>–2</sup>}} given by Lainey et al. (2023), divided by the [[gravitational constant]] ''G'' {{=}} {{val|6.6743|e=-2|u=km<sup>3</sup>·kg<sup>–1</sup>·s<sup>–2</sup>}}.{{sfn|Lainey et al.|2023}}}}
| density = {{val|0.3935|0.0033|u=g/cm3}}{{sfn|Lainey et al.|2023}}{{rp|page=4}}
| surface_grav = {{val|0.0001|-|0.0017|u=m/s2}}{{sfn|Thomas & Helfenstein|2020}}{{rp|page=3}}
| escape_velocity = {{V2|5.490e-6|20.4|3}}&nbsp;km/s at longest axis<br/>to {{V2|5.490e-6|9.3|3}}&nbsp;km/s at poles<!-- V2 template uses mass in terms of e+21 kg, radius in terms of km, and number of decimal places -->
| rotation = [[synchronous rotation|synchronous]]
| axial_tilt = zero
| albedo = 0.4
| single_temperature = ≈&thinsp;81 K
}}

'''Atlas''' is an [[inner satellite]] of [[Saturn]] which was discovered by [[Richard Terrile]] in 1980  from [[Voyager program|Voyager]] photos and was designated '''{{nowrap|S/1980 S 28}}'''.{{sfn|IAUC 3539}} In 1983 it was officially named after [[Atlas (mythology)|Atlas]] of [[Greek mythology]], because it "holds the rings on its shoulders" like the [[Titan (mythology)|Titan]] Atlas held the sky up above the [[Earth]].{{sfn|IAUC 3872}} It is also designated '''{{nowrap|Saturn XV}}'''.

Atlas is the closest satellite to the sharp outer edge of the [[Rings of Saturn#A Ring|A ring]], and was long thought to be a [[shepherd satellite]] for this ring. However, now it is known that the outer edge of the ring is instead maintained by a 7:6 [[orbital resonance]] with the larger but more distant moons [[Janus (moon)|Janus]] and [[Epimetheus (moon)|Epimetheus]].{{sfn|Lakdawalla|2007}} In 2004 a faint, thin ring, temporarily designated {{nowrap|[[R/2004 S 1]]}}, was discovered in the Atlantean orbit.{{sfn|IAUC 8401}}

High-resolution images taken in June 2005 by ''[[Cassini–Huygens|Cassini]]'' revealed Atlas to have a roughly spherical centre surrounded by a large, smooth [[equatorial ridge]]. The most likely explanation for this unusual and prominent structure is that ring material swept up by the moon accumulates on the moon, with a strong preference for the equator due to the ring's thinness. The size of the equatorial ridge is comparable with the expected [[Roche lobe]] of the moon, which means that for any additional particles impacting the equator, the [[centrifugal force]] will nearly overcome Atlas's tiny gravity, and they will probably be lost.{{sfn|Lakdawalla|2007}}

Atlas is significantly perturbed by [[Prometheus (moon)|Prometheus]] and to a lesser degree by [[Pandora (moon)|Pandora]], leading to excursions in longitude of up to 600&nbsp;km (~0.25°) away from the precessing Keplerian orbit with a rough period of about 3 years. Because the orbits of Prometheus and Pandora are chaotic, it is suspected that Atlas's may be as well.{{sfn|Spitale Jacobson et al.|2006}}

== Gallery ==
<gallery widths=180>
File:Cassini Atlas N00084634 CL.png|Atlas from above its south pole (June 12, 2007)
File:Atlas Rev09.2x.jpg|Atlas - ''Cassini''<br />(June 8, 2005).
File:Atlas with rings.jpg|Atlas - [[Rings of Saturn#A Ring|A]] and [[Rings of Saturn#F Ring|F]] rings<br />(June 30, 2006).
File:PIA17206-SaturnMoon-Atlas-Flyby-20151206.jpg|Atlas near the A ring<br />(December 6, 2015).
File:F Ring and Atlas PIA10448.jpg|Atlas near the F ring<br />(May 9, 2005).
</gallery>

== Notes ==
{{notelist}}

== References ==

=== Citations ===

{{reflist}}

=== Sources ===

* {{cite journal
  | last = Green
  | first = Daniel W. E.
  | title = S/2004 S 3, S/2004 S 4, and R/2004 S 1
  | date = September 9, 2004
  | journal = IAU Circular
  | volume = 8401
  | page = 1
 | url = http://www.cbat.eps.harvard.edu/iauc/08400/08401.html
  | access-date = 2011-12-30
  | ref = {{sfnRef|IAUC 8401}}
  | bibcode = 2004IAUC.8401....1P
 }}
* {{cite web
  | last = Lakdawalla
  | first = Emily
  | date = June 13, 2007
  | title = Funny little Atlas
  | work = The [[Planetary Society]] weblog
  | url = http://www.planetary.org/blog/article/00001003/
  | access-date = 2011-12-30
  }}
* {{cite journal
 |last=Marsden
 |first=Brian G.
 |title=1980 S 28
 |date=November 13, 1980
 |format=discovery
 |journal=IAU Circular
 |volume=3539
 |page=2
 |url=http://www.cbat.eps.harvard.edu/iauc/03500/03539.html
 |access-date=2011-12-30
 |ref={{sfnRef|IAUC 3539}}

|archive-url=https://web.archive.org/web/20111213152218/http://www.cbat.eps.harvard.edu/iauc/03500/03539.html
 |archive-date=2011-12-13
|bibcode=1980IAUC.3539....2M
 }}
* {{cite journal
  | last = Marsden
  | first = Brian G.
  | title = Satellites of Jupiter and Saturn
  | date = September 30, 1983
  | format = naming the moon
  | journal = IAU Circular
  | volume = 3872
  | url = http://www.cbat.eps.harvard.edu/iauc/03800/03872.html
  | access-date = 2011-12-30
  | ref = {{sfnRef|IAUC 3872}}
  }}
* {{cite journal| doi = 10.1086/505206| last1 = Spitale| first1 = J. N.| last2 = Jacobson| first2 = R. A.| last3 = Porco| first3 = C. C.| last4 = Owen| first4 = W. M. Jr.| year = 2006| title = The orbits of Saturn's small satellites derived from combined historic and ''Cassini'' imaging observations| journal = The Astronomical Journal| volume = 132| issue = 2| pages = 692–710| bibcode = 2006AJ....132..692S| ref = {{sfnRef|Spitale Jacobson et al.|2006}}| doi-access = free}}
* {{cite journal| doi = 10.1016/j.icarus.2010.01.025| last1 = Thomas| first1 = P. C.| date = July 2010| title = Sizes, shapes, and derived properties of the saturnian satellites after the Cassini nominal mission| journal = Icarus| volume = 208| issue = 1| pages = 395–401| url = http://www.ciclops.org/media/sp/2011/6794_16344_0.pdf| bibcode = 2010Icar..208..395T| access-date = 2015-09-04| archive-date = 2018-12-23| archive-url = https://web.archive.org/web/20181223003125/http://www.ciclops.org/media/sp/2011/6794_16344_0.pdf}}
* {{cite journal
  |ref = {{sfnRef|Thomas & Helfenstein|2020}}
  |first1 = P. C. |last1 = Thomas
  |first2 = P. |last2 = Helfenstein
  |title      = The small inner satellites of Saturn: Shapes, structures and some implications
  |journal    = Icarus
  |date       = July 2020
  |volume     = 344
  |id         = 113355
  |page      = 20
  |doi        = 10.1016/j.icarus.2019.06.016
  |bibcode    = 2020Icar..34413355T|s2cid = 197474587 }}
* {{cite journal
  |ref = {{sfnRef|Lainey et al.|2023}}
  |first1 = V. |last1 = Lainey
  |first2 = N. |last2 = Rambaux
  |first3 = N. |last3 = Cooper
  |first4 = R. |last4 = Dahoumane
  |first5 = Q. |last5 = Zhang
  |title      = Characterising the interior of five inner Saturnian moons using Cassini ISS data
  |journal    = Astronomy & Astrophysics
  |date       = February 2023
  |volume     = 670
  |id         = L25
  |page      = 6
  |doi-access = free
  |doi        = 10.1051/0004-6361/202244757
  |bibcode    = 2023A&A...670L..25L}}

== External links ==

{{Commons category|Atlas (moon)}}
{{Spoken Wikipedia|Atlas (moon).ogg|date=2010-01-13}}
* [https://web.archive.org/web/20070609074757/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sat_Atlas Atlas Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [https://web.archive.org/web/20060830142335/http://www.planetary.org/explore/topics/saturn/atlas.html The Planetary Society: Atlas]
* [https://web.archive.org/web/20041031221550/http://sse.jpl.nasa.gov/planets/profile.cfm?Object=Sat_Atlas&Display=Facts NASA factsheet]

{{Moons of Saturn}}
{{Saturn}}

{{DEFAULTSORT:Atlas (Moon)}}
[[Category:Moons of Saturn]]
[[Category:Astronomical objects discovered in 1980]]
[[Category:Atlas (mythology)]]
[[Category:Moons with a prograde orbit]]