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S/2009 S 1

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Small moonlet in Saturn's B ring

S/2009 S 1
Discovery^[1]
Cassini image ofS/2009 S 1 as a bright dot casting a long shadow overSaturn'sB Ring
Discovered by	Cassini Imaging Team
Discovery date	2009
Orbital characteristics^[2]
Semi-major axis	116914 km
Eccentricity	≈ 0.000
Orbital period (sidereal)	0.4715 d (11.32 h)
Inclination	≈ 0.0
Satellite of	Saturn
Group	outer B ring moonlet
Physical characteristics
Mean diameter	0.3 km^[3]
Synodic rotation period	assumed synchronous

S/2009 S 1 is amoonlet embedded in the outer part ofSaturn'sB Ring, orbiting 117,000 km (73,000 mi) away from the planet. The moonlet was discovered by theCassini Imaging Team during the Saturnianequinox event on 26 July 2009, when theCassini spacecraft imaged the moonlet casting a 36 km (22 mi)-long shadow onto the B Ring.^[4] With a diameter of 300 m (1,000 ft), it is most likely a long-lived solid body, which would count it as the smallest and innermost known moon of Saturn (as well as being the smallest knownnatural satellite in theSolar System).^[4]

Discovery

[edit]

A wider perspective of the image above. S/2009 S 1 is in the center. TheCassini Division is on the right.

S/2009 S 1 was first identified by theCassini Imaging Team led byCarolyn Porco,^[5] in a single image taken by theCassini spacecraft approximately 296,000 km (184,000 mi) from Saturn on 26 July 2009 11:30UTC.^[4]^[6] The moonlet was discovered during Saturn's 2009equinox, when it cast an approximately 36 km (22 mi)-long shadow on the planet's B ring.

Characteristics

[edit]

Based on the shadow's width, theCassini Imaging Team infer a diameter of 300 m (1,000 ft) forS/2009 S 1.^[7] The presence of a shadow suggests that theS/2009 S 1 is most likely a solid body large enough to have existed since the formation of the B ring.^[3] This particular moon isone of the smallest moons of Saturn that has been directly imaged.^[4]

S/2009 S 1 is located about 650 km (400 mi) interior to the edge of the B ring, corresponding to a radial distance of 116,914 ± 17 km (72,647 ± 11 mi) from the center of Saturn. The moonlet protrudes 150 m (500 ft) above the B ring plane, which has a vertical thickness of 5 m (16 ft) for comparison.^[3]

Although it is embedded in the B ring,S/2009 S 1 does not appear to produce extensive, propeller-shaped disturbance features unlike thepropeller moonlets in Saturn's A ring. This may be because the B ring is very dense at the moonlet's location, which would hinder the formation of visible propeller gaps around the moonlet.^[4]^[3]^[8]

References

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^"Planetary Satellite Discovery Circumstances". Jet Propulsion Laboratory. Retrieved28 March 2022.
^Williams, David R. (15 October 2019)."Saturnian Satellite Fact Sheet".Space Science Data Coordinated Archive. NASA. Retrieved28 March 2022.
^^a ^b ^c ^dSpitale, J. N.; Porco, C. C. (December 2010)."Detection of Free Unstable Modes and Massive Bodies in Saturn's Outer B Ring".The Astronomical Journal.140 (6):1747–1757.arXiv:0912.3489.Bibcode:2010AJ....140.1747S.doi:10.1088/0004-6256/140/6/1747.S2CID 117319280.
^^a ^b ^c ^d ^e"A Small Find Near Equinox".Cassini Solstice Mission. Jet Propulsion Laboratory. 7 August 2009. Archived fromthe original on 9 August 2009. Retrieved2 January 2012.
^"Cassini Imaging Science Team".Cassini Imaging Central Laboratory for OPerationS (CICLOPS). Archived fromthe original on 20 May 2011. Retrieved2 January 2012.
^"Image of Saturn-rings".Solar System Exploration. NASA. 26 July 2009.Archived from the original on 27 November 2020. Retrieved28 March 2022.
^Porco, C. & the Cassini Imaging Team (2 November 2009). Green, D. W. E. (ed.)."S/2009 S1".IAU Circular.9091 (1): 1.Bibcode:2009IAUC.9091....1P.Archived from the original on 11 June 2011. Retrieved2 January 2012.
^Michikoshi, Shugo; Kokubo, Eiichiro (May 2011)."Formation of a Propeller Structure by a Moonlet in a Dense Planetary Ring".The Astrophysical Journal Letters.732 (2): 4.arXiv:1104.0462.Bibcode:2011ApJ...732L..23M.doi:10.1088/2041-8205/732/2/L23.S2CID 18889201. L23.

Moons of Saturn

Listed in approximate increasing distance from Saturn

Ring moonlets

Ring shepherds

Alkyonides

Large moons
(withtrojans)

Inuit group (36)

Kiviuq subgroup (20)	S/2023 S 1 S/2019 S 1 S/2004 S 54 S/2004 S 55 S/2020 S 11 S/2019 S 22 Kiviuq S/2023 S 2 S/2019 S 23 S/2020 S 12 S/2005 S 4 S/2019 S 25 S/2020 S 1 Ijiraq S/2019 S 24 S/2007 S 10 S/2019 S 26 S/2020 S 13 S/2023 S 6 S/2023 S 7
Paaliaq	Paaliaq
Siarnaq subgroup (15)	S/2004 S 31 S/2023 S 19 S/2023 S 3 S/2020 S 19 Tarqeq S/2019 S 14 Siarnaq S/2019 S 32 S/2020 S 3 S/2005 S 6 S/2019 S 6 S/2004 S 58 S/2006 S 23 S/2020 S 5 S/2023 S 22

Gallic group (17)

Albiorix
S/2020 S 15
Bebhionn
S/2007 S 8
Saturn LX
S/2019 S 29
S/2023 S 18
S/2023 S 17
S/2007 S 11
Erriapus
S/2019 S 31
Tarvos
S/2020 S 4
S/2019 S 34
S/2005 S 7
S/2006 S 12
S/2004 S 24

Norse group (197)

Low-inclination (12)	S/2023 S 38 Skathi S/2020 S 17 S/2023 S 20 S/2023 S 30 Hyrrokkin Narvi S/2019 S 37 Bestla S/2019 S 11 S/2020 S 27 S/2023 S 46
Kari subgroup (15)	S/2006 S 1 S/2004 S 45 S/2023 S 27 S/2006 S 3 S/2023 S 33 S/2020 S 30 Kari Geirrod S/2019 S 17 S/2019 S 19 S/2019 S 18 S/2004 S 21 S/2004 S 36 S/2019 S 20 S/2006 S 29
Mundilfari subgroup (143)	S/2023 S 50 S/2023 S 9 S/2004 S 56 S/2023 S 8 S/2023 S 11 S/2006 S 21 S/2006 S 22 S/2023 S 13 S/2023 S 10 S/2023 S 12 S/2007 S 5 S/2007 S 7 S/2004 S 37 S/2004 S 47 S/2004 S 40 S/2020 S 14 S/2019 S 27 S/2023 S 14 S/2020 S 16 S/2023 S 16 S/2019 S 3 S/2020 S 7 S/2019 S 28 Skoll S/2019 S 30 S/2023 S 21 S/2023 S 4 S/2020 S 18 S/2020 S 2 S/2019 S 4 S/2020 S 20 S/2004 S 41 S/2004 S 57 S/2006 S 24 S/2004 S 42 S/2023 S 15 S/2023 S 24 S/2004 S 13 S/2007 S 6 S/2019 S 35 S/2006 S 25 Mundilfari S/2006 S 26 S/2019 S 33 S/2023 S 23 S/2020 S 21 S/2004 S 43 S/2006 S 10 S/2019 S 5 S/2023 S 25 S/2004 S 59 S/2006 S 27 Gridr Bergelmir Jarnsaxa S/2023 S 44 S/2020 S 22 S/2004 S 44 Hati S/2004 S 17 S/2004 S 12 S/2020 S 23 Eggther S/2023 S 28 S/2023 S 37 S/2023 S 26 S/2019 S 36 S/2006 S 13 S/2023 S 48 S/2023 S 29 S/2007 S 9 Farbauti S/2019 S 9 S/2023 S 32 S/2020 S 24 Aegir S/2019 S 10 Beli S/2023 S 31 S/2020 S 25 S/2023 S 34 S/2023 S 39 S/2019 S 12 S/2004 S 61 S/2006 S 14 S/2023 S 40 Gunnlod S/2019 S 15 S/2020 S 6 S/2020 S 26 S/2023 S 41 S/2004 S 7 S/2005 S 5 S/2006 S 16 S/2023 S 49 S/2006 S 15 S/2023 S 42 S/2004 S 28 S/2020 S 32 S/2020 S 8 S/2020 S 28 S/2019 S 38 S/2004 S 48 S/2023 S 36 S/2023 S 35 S/2020 S 29 Fenrir S/2004 S 50 S/2006 S 17 S/2004 S 49 S/2020 S 34 S/2020 S 31 S/2023 S 43 Surtur S/2006 S 18 S/2020 S 36 Loge S/2020 S 33 S/2004 S 39 S/2019 S 16 S/2004 S 53 S/2023 S 45 Thiazzi S/2020 S 38 S/2020 S 40 S/2019 S 40 S/2019 S 42 Saturn LXIV S/2020 S 39 S/2019 S 41 Fornjot S/2023 S 47 S/2004 S 51 S/2020 S 10 S/2020 S 42 S/2020 S 9 S/2023 S 5 S/2020 S 41 S/2019 S 21 S/2004 S 52 S/2020 S 43 S/2019 S 43 S/2020 S 44
Phoebe subgroup (27)	Phoebe S/2006 S 20 S/2006 S 9 S/2007 S 2 S/2019 S 2 Greip Suttungr S/2004 S 60 S/2007 S 3 S/2006 S 11 S/2019 S 7 S/2019 S 8 Thrymr S/2004 S 46 Angrboda Gerd S/2019 S 13 Skrymir S/2006 S 28 Alvaldi Ymir S/2020 S 35 S/2020 S 37 S/2019 S 39 S/2006 S 19 Saturn LVIII S/2019 S 44

v t e Saturn
Outline
Geography	Dragon Storm Great White Spot Saturn Electrostatic Discharges Hexagon Magnetosphere Rings
Moons	S/2009 S 1 Ring moonlets Pan Daphnis Atlas Prometheus Pandora Epimetheus Janus Aegaeon Mimas Methone Anthe Pallene Enceladus Tethys Telesto Calypso Dione Helene Polydeuces Rhea Titan Hyperion Iapetus Inuit group Kiviuq Paaliaq Siarnaq Gallic group Albiorix Norse group Phoebe
Astronomy	Delta Octantis Saturn-crossing minor planets Solar eclipses on Saturn
Exploration	Cassini–Huygens (Huygens) timeline retirement Pioneer 11 Voyager program Voyager 1 Voyager 2
Related	Fiction The Day the Earth Smiled In Saturn's Rings (2018 documentary)
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