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{{short description|Possible dwarf planet}}
{{Short description|Possible dwarf planet}}
{{Infobox planet
{{Infobox planet
| minorplanet = yes
| minorplanet = yes
| name = 120347 Salacia
| name = 120347 Salacia
| symbol = [[File:Salacia symbol (Moskowitz, bold).svg|24px]]
| symbol = [[File:Salacia symbol (bold).svg|24px]] or [[File:Salacia symbol (bold, Greek).svg|24px]] (rare)
| background = #C2E0FF
| background = #C2E0FF
|image = Salacia and Actaea Keck-NIRC2.jpg
|image = Salacia and Actaea Keck-NIRC2.jpg
|image_size = 250
|image_scale =
|caption = [[Keck Observatory|Keck Telescope]] image of Salacia (bright, center) and its moon [[Actaea (moon)|Actaea]] (faint, at left)
|caption = [[Keck Observatory|Keck Telescope]] image of Salacia (bright, center) and its moon [[Actaea (moon)|Actaea]] (faint, at left)
| discovery_ref = <ref name="jpldata" /><ref name="MPC-Salacia" />
| discovery_ref = <ref name="jpldata" /><ref name="MPC-Salacia" />
| discoverer = [[Henry G. Roe|H. G. Roe]]<br />[[Michael E. Brown|M. E. Brown]]<br />[[Kristina M. Barkume|K. M. Barkume]]
| discoverer = [[Henry G. Roe|H. G. Roe]]<br />[[Michael E. Brown|M. E. Brown]]<br />K. M. Barkume
| discovery_site = [[Palomar Observatory|Palomar Obs.]]
| discovery_site = [[Palomar Observatory|Palomar Obs.]]
| discovered = 22 September 2004
| discovered = 22 September 2004
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| avg_speed =
| avg_speed =
| satellites = 1 {{small|([[Actaea (moon)|Actaea]])}}
| satellites = 1 {{small|([[Actaea (moon)|Actaea]])}}
| mean_diameter = {{val|846|21|u=km}}<ref name="Grundy-orbits"/>{{efn|approximation if Salacia and Actaea were both spherical and had the same albedo}}<br />{{val|854|45|u=km}} {{small|(equal albedos)}}<ref name=TNOsCool8/><br/>{{val|866|37|u=km}}<ref name="Brown2017"/>
| mean_diameter = {{val|846|21|u=km}}<ref name="Grundy-orbits"/>{{efn|approximation if Salacia and Actaea were both spherical and had the same albedo}}<br/>{{val|866|37|u=km}}<ref name="Brown2017"/>
| mass = {{val|4.922|0.071|e=20|u=kg}} (system)<ref name="Grundy-orbits"/><br />{{val|4.38|0.16|e=20|u=kg}} (system mass)<ref name=TNOsCool8/><ref name="Stansberry-result"/>
| mass = {{val|4.922|0.071|e=20|u=kg}} (system)<ref name="Grundy-orbits"/>
| density = {{val|1.5|0.12|u=g/cm3}}<ref name="Grundy-orbits"/><br />{{nowrap|{{val|1.29|+0.29|-0.23|u=g/cm3}} (system)<ref name=TNOsCool8/>}}<br/>{{val|1.26|0.16|u=g/cm3}}<ref name="Brown2017"/>
| density = {{val|1.5|0.12|u=g/cm3}}<ref name="Grundy-orbits"/><br/>{{val|1.26|0.16|u=g/cm3}}<ref name="Brown2017"/>
| sidereal_day = 6.09 h<ref name="jpldata"/>
| sidereal_day = 6.09 h<ref name="jpldata"/>
| spectral_type = [[Trans-Neptunian object#Color indices|BB]]<ref name="Belskaya2015"/><br/>B−V={{val|0.66|0.06}}<ref name="Belskaya2015"/><br/>V−R={{val|0.40|0.04}}<ref name="Belskaya2015"/><br/>V−I={{val|0.83|0.04}}<ref name="Belskaya2015"/>
| spectral_type = [[Trans-Neptunian object#Color indices|BB]]<ref name="Belskaya2015"/><br/>B−V={{val|0.66|0.06}}<ref name="Belskaya2015"/><br/>V−R={{val|0.40|0.04}}<ref name="Belskaya2015"/><br/>V−I={{val|0.83|0.04}}<ref name="Belskaya2015"/>
| albedo = {{val|0.044|0.004}}<ref name=TNOsCool8/><br/>{{val|0.042|0.004}}<ref name="Brown2017"/>
| albedo = {{val|0.042|0.004}}<ref name="Brown2017"/>
| rotation = {{Convert|6.09|h|d|abbr=on|lk=on}}
| rotation = {{Convert|6.09|h|d|abbr=on|lk=on}}
| abs_magnitude = {{val|4.360|0.011}} (system)<ref name="Stansberry-result"/><br />{{val|4.476|0.013}} (Salacia)<ref name="Stansberry-result"/><br />{{val|6.850|0.053}} (Actaea)<ref name="Stansberry-result"/><br />3.9<ref name="jpldata"/>
| abs_magnitude = {{val|4.360|0.011}} (system)<ref name="Stansberry-result"/><br />{{val|4.476|0.013}} (Salacia)<ref name="Stansberry-result"/><br />{{val|6.850|0.053}} (Actaea)<ref name="Stansberry-result"/><br />3.9<ref name="jpldata"/>
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}}
}}


'''120347 Salacia''', provisional designation {{mp|2004 SB|60}}, is a large planetoid in the [[Kuiper belt]], approximately 850 kilometers in diameter. As of 2018, it is located 44.8 [[astronomical unit]]s from the [[Sun]], and reaches [[apparent magnitude]] 20.7 at [[opposition (astronomy)|opposition]].
'''Salacia''' ([[minor-planet designation]]: '''120347 Salacia''') is a large [[trans-Neptunian object]] (TNO) in the [[Kuiper belt]], approximately {{cvt|850|km}} in diameter. It was discovered on 22 September 2004, by American astronomers [[Henry G. Roe|Henry Roe]], [[Michael E. Brown|Michael Brown]] and Kristina Barkume at the [[Palomar Observatory]] in California, United States. Salacia orbits the Sun at an average distance that is slightly greater than that of [[Pluto]]. It was named after the Roman goddess [[Salacia (mythology)|Salacia]] and has a single known moon, [[Actaea (moon)|Actaea]].


⚫
Brown estimated that Salacia is nearly certainly a [[dwarf planet]].<ref name="Brown-dplist"/> However, William Grundy ''et al.'' argue that objects in the size range of 400–1,000&nbsp;km, with densities of ≈&nbsp;1.2 g/cm<sup>3</sup> or less and albedos less than ≈&nbsp;0.2, have likely never compressed into fully solid bodies or been resurfaced, let alone differentiated or collapsed into hydrostatic equilibrium, and so are highly unlikely to be dwarf planets.<ref name=Grundy2019>W.M. Grundy, K.S. Noll, M.W. Buie, S.D. Benecchi, D. Ragozzine & H.G. Roe, 'The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ({{mp|(229762) 2007 UK|126}})', ''Icarus'' [http://www2.lowell.edu/~grundy/abstracts/2019.G-G.html (forthcoming, available online 30 March 2019)] {{Webarchive|url=https://web.archive.org/web/20190407045334/http://www2.lowell.edu/~grundy/abstracts/2019.G-G.html |date=7 April 2019 }} DOI: 10.1016/j.icarus.2018.12.037,</ref> Salacia is at the upper end of this size range and has a very low [[albedo]], though Grundy ''et al.'' later found it to have the relatively high density of {{val|1.5|0.1|u=g/cm3}}.<ref name="Grundy-orbits"/>
Salacia was discovered on 22 September 2004, by American astronomers [[Henry G. Roe|Henry Roe]], [[Michael E. Brown|Michael Brown]] and [[Kristina M. Barkume|Kristina Barkume]] at the [[Palomar Observatory]] in California, United States. It has been observed 124 times, with [[precovery]] images back to 25 July 1982.<ref name="MPC-Salacia" /> Salacia orbits the Sun at an average distance that is slightly greater than that of [[Pluto]]. It was named after the Roman goddess [[Salacia (mythology)|Salacia]] and has a single known moon, [[Actaea (moon)|Actaea]].

⚫
Brown estimated that Salacia is nearly certainly a [[dwarf planet]].<ref name="Brown-dplist"/> However, William Grundy ''et al.'' argue that objects in the size range of 400–1,000&nbsp;km, with densities of ≈&nbsp;1.2 g/cm<sup>3</sup> or less and albedos less than ≈&nbsp;0.2, have likely never compressed into fully solid bodies or been resurfaced, let alone differentiated or collapsed into hydrostatic equilibrium, and so are highly unlikely to be dwarf planets.<ref name=Grundy2019>W.M. Grundy, K.S. Noll, M.W. Buie, S.D. Benecchi, D. Ragozzine & H.G. Roe, 'The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ({{mp|(229762) 2007 UK|126}})', ''Icarus'' [http://www2.lowell.edu/~grundy/abstracts/2019.G-G.html (forthcoming, available online 30 March 2019)] {{Webarchive|url=https://web.archive.org/web/20190407045334/http://www2.lowell.edu/~grundy/abstracts/2019.G-G.html |date=7 April 2019 }} DOI: 10.1016/j.icarus.2018.12.037,</ref> Salacia is at the upper end of this size range and has a very low albedo, though Grundy ''et al.'' later found it to have the relatively high density of {{val|1.5|0.1|u=g/cm3}}.<ref name="Grundy-orbits"/>


== Orbit ==
== Orbit ==


[[File:Salacia_orbit_2018.png|left|thumb|The orbit of Salacia is similar to [[Pluto]], except for a near opposite [[longitude of ascending node]]. Its current position is near its most northern position above the ecliptic.]]
[[File:Salacia_orbit_2018.png|left|thumb|The orbit of Salacia is similar to [[Pluto]]'s, except for a near opposite [[longitude of ascending node]]. Its current position is near its most northern position above the ecliptic.]]


Salacia is a non-resonant object with a moderate eccentricity (0.11) and large inclination (23.9°), making it a [[scattered disc|scattered–extended object]] in the classification of the [[Deep Ecliptic Survey]] and a [[classical Kuiper belt object#Orbits: 'hot' and 'cold' populations|hot classical]] Kuiper belt object in the classification system of Gladman ''et al.'',<ref name=Gladman-classification/> which may be the same thing if they are part of a single population that formed during the [[Nice model|outward migration of Neptune]].<ref name="Stansberry-result"/> Salacia's orbit is within the [[parameter space]] of the [[Haumea family|Haumea collisional family]], but Salacia is not part of it, as evidenced by the lack of the strong water-ice absorption bands of members of the collisional family.<ref name="Stansberry-result"/>
Salacia is a non-resonant object with a moderate eccentricity (0.11) and large inclination (23.9°), making it a [[scattered disc|scattered–extended object]] in the classification of the [[Deep Ecliptic Survey]] and a [[classical Kuiper belt object#Orbits: 'hot' and 'cold' populations|hot classical]] Kuiper belt object in the classification system of Gladman ''et al.'',<ref name=Gladman-classification/> which may be the same thing if they are part of a single population that formed during the [[Nice model|outward migration of Neptune]].<ref name="Stansberry-result"/> Salacia's orbit is within the [[parameter space]] of the [[Haumea family|Haumea collisional family]], but Salacia is not part of it, as evidenced by its lack of the strong water-ice absorption bands.<ref name="Stansberry-result"/>


== Physical characteristics ==
== Physical characteristics ==


As of 2019, the total mass of the Salacia–Actaea system is estimated at {{val|4.922|0.071|e=20|u=kg}}, with an average system density of {{val|1.51|u=g/cm3}}; Salacia itself is estimated to be around 846&nbsp;km in diameter.<ref name="Grundy-orbits"/> Salacia has the lowest [[albedo]] of any known large [[trans-Neptunian object]].<ref name="Stansberry-result" /> According to the estimate from 2017 based on an improved thermophysical modelling, the size of Salacia is slightly larger at 866 km and its density therefore slightly lower (calculated at {{val|1.26|u=g/cm3}} with the old mass estimate discussed below).<ref name="Brown2017"/>
As of 2019, the total mass of the Salacia–Actaea system is estimated at {{val|4.922|0.071|e=20|u=kg}}, with an average system density of {{val|1.51|u=g/cm3}}; Salacia itself is estimated to be around 846&nbsp;km in diameter.<ref name="Grundy-orbits"/> Salacia has the lowest albedo of any known large [[trans-Neptunian object]].<ref name="Stansberry-result" /> According to the estimate from 2017 based on an improved thermophysical modelling, the size of Salacia is slightly larger at 866&nbsp;km and its density therefore slightly lower (calculated at {{val|1.26|u=g/cm3}} with the old mass estimate discussed below).<ref name="Brown2017"/>


Salacia was previously believed to have a mass of around {{val|4.38|0.16|e=20|u=kg}}, in which case it would also have had the lowest density (around {{val|1.29|u=g/cm3}}) of any known large TNO;<ref name="TNOsCool8"/> William Grundy and colleagues proposed that this low density would imply that Salacia never collapsed into a solid body, in which case it would not be in [[hydrostatic equilibrium]].<ref name=Grundy2019/> Salacia's [[infrared spectrum]] is almost featureless, indicating an abundance of water ice of less than 5% on the surface.<ref name=TNOsCool8 /><ref name="Schaller2008" /> Its [[light curve|light-curve]] amplitude is only 3%.<ref name="Stansberry-result" />
Salacia was previously believed to have a mass of around {{val|4.38|0.16|e=20|u=kg}}, in which case it would also have had the lowest density (around {{val|1.29|u=g/cm3}}) of any known large TNO;<ref name="TNOsCool8"/> William Grundy and colleagues proposed that this low density would imply that Salacia never collapsed into a solid body, in which case it would not be in [[hydrostatic equilibrium]].<ref name=Grundy2019/> Salacia's [[infrared spectrum]] is almost featureless, indicating an abundance of water ice of less than 5% on the surface.<ref name=TNOsCool8 /><ref name="Schaller2008" /> [[Near-infrared]] [[spectroscopy]] by the [[James Webb Space Telescope]] (JWST) in 2022 revealed the presence of water ice in Salacia's surface.<ref name="Cook2023"/> No signs of [[Volatile (astrogeology)|volatile]] ices such as [[methane]] were detected in JWST's spectrum of Salacia.<ref name="Cook2023"/> Its [[light curve|light-curve]] amplitude is only 3%.<ref name="Stansberry-result" />


==Satellite ==
==Satellite ==
{{main|Actaea (moon)}}

Salacia has one known [[Asteroid moon|natural satellite]], '''[[Actaea (moon)|Actaea]]''', that orbits its primary every {{val|5.49380|0.00016|u=d}} at a distance of {{val|5619|89|u=km}}<!-- uncertainty from the body, no abstract--> and with an eccentricity of {{val|0.0084|0.0076}}. It was discovered on 21 July 2006 by Keith Noll, [[Harold Levison]], [[Denise Stephens]] and William Grundy with the [[Hubble Space Telescope]].<ref name=IAUC8751/>
Salacia has one known [[Asteroid moon|natural satellite]], '''[[Actaea (moon)|Actaea]]''', that orbits its primary every {{val|5.49380|0.00016|u=d}} at a distance of {{val|5619|89|u=km}}<!-- uncertainty from the body, no abstract--> and with an eccentricity of {{val|0.0084|0.0076}}. It was discovered on 21 July 2006 by Keith Noll, [[Harold Levison]], [[Denise Stephens]] and William Grundy with the [[Hubble Space Telescope]].<ref name=IAUC8751/>


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== Name ==
== Name ==


This planetoid was named after [[Salacia (mythology)|Salacia]] ({{IPAc-en|s|ə|ˈ|l|eɪ|ʃ|ə}}), the goddess of salt water and the wife of [[Neptune (mythology)|Neptune]].<ref name="MPC-Salacia" /> The naming citation was published on 18 February 2011 ({{small|[[Minor Planet Circulars|M.P.C.]] 73984}}).<ref name="MPC-Circulars-Archive" />
This minor planet was named after [[Salacia (mythology)|Salacia]] ({{IPAc-en|s|ə|ˈ|l|eɪ|ʃ|ə}}), the goddess of salt water and the wife of [[Neptune (mythology)|Neptune]].<ref name="MPC-Salacia" /> The naming citation was published on 18 February 2011 ({{small|[[Minor Planet Circulars|M.P.C.]] 73984}}).<ref name="MPC-Circulars-Archive" />


The moon's name, ''Actaea'' {{IPAc-en|æ|k|ˈ|t|iː|ə}}, was assigned on the same date. [[Nereid|Actaea]] is a [[nereid]] or sea nymph.
The moon's name, [[Actaea (Greek mythology)|Actaea]] {{IPAc-en|æ|k|ˈ|t|iː|ə}}, was assigned on the same date. Actaea is a [[nereid]] or sea nymph.


[[Planetary symbol]]s are no longer much used in astronomy, so Salacia never received a symbol in the astronomical literature. There is no standard symbol for Salacia used by astrologers either. Denis Moskowitz, a software engineer in Massachusetts who designed the symbols for most of the dwarf planets, proposed a stylised [[hippocamp]] ([[File:Salacia symbol (Moskowitz, fixed width).svg|16px]]) as the symbol for Salacia, befitting Salacia as Neptune's consort.<ref name=miller>{{cite web|url=https://www.unicode.org/L2/L2021/21224-dwarf-planet-syms.pdf|title=Unicode request for dwarf-planet symbols|last=Miller|first=Kirk|date=26 October 2021|website=unicode.org}}</ref>
[[Planetary symbol]]s are no longer used much in astronomy, so Salacia never received a symbol in the astronomical literature. Denis Moskowitz, a software engineer who designed most of the dwarf planet symbols, proposed a stylised [[hippocamp]] ([[File:Salacia symbol (fixed width).svg|16px]], formerly [[File:Salacia symbol (fixed width, Greek).svg|16px]]) as the symbol for Salacia;<ref name=miller>{{cite web|url=https://www.unicode.org/L2/L2021/21224-dwarf-planet-syms.pdf|title=Unicode request for dwarf-planet symbols|last=Miller|first=Kirk|date=26 October 2021|website=unicode.org|access-date=18 October 2022|archive-date=23 March 2022|archive-url=https://web.archive.org/web/20220323174107/https://www.unicode.org/L2/L2021/21224-dwarf-planet-syms.pdf|url-status=live}}</ref><ref>{{cite web |url=https://www.unicode.org/L2/L2024/24235-constellation-symbols.pdf |title=Preliminary presentation of constellation symbols |last=Miller |first=Kirk |date=18 October 2024 |website=unicode.org |publisher=The Unicode Consortium |access-date=22 October 2024 |quote=}}</ref> this symbol is not widely used.


==See also==
==See also==
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<ref name="jpldata">{{cite web
<ref name="jpldata">{{cite web
|type = 2019-09-21 last obs.
|type = 2019-09-21 last obs.
|title = JPL Small-Body Database Browser: 120347 Salacia (2004 SB60)
|title = JPL Small-Body Database Browser: 120347 Salacia (2004 SB60)
|url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2120347
|url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2120347
|publisher = [[Jet Propulsion Laboratory]]
|publisher = [[Jet Propulsion Laboratory]]
|date = 7 November 2019
|date = 7 November 2019
|access-date = 20 February 2020}}</ref>
|access-date = 20 February 2020
|archive-date = 3 April 2017
|archive-url = https://web.archive.org/web/20170403194747/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2120347
|url-status = live
}}</ref>


<ref name="MPC-Salacia">{{cite web
<ref name="MPC-Salacia">{{cite web
|title = 120347 Salacia (2004 SB60)
|title = 120347 Salacia (2004 SB60)
|work = Minor Planet Center
|work = Minor Planet Center
|url = https://www.minorplanetcenter.net/db_search/show_object?object_id=120347
|url = https://www.minorplanetcenter.net/db_search/show_object?object_id=120347
|access-date = 22 July 2018}}</ref>
|access-date = 22 July 2018
|archive-date = 3 April 2017
|archive-url = https://web.archive.org/web/20170403112159/http://www.minorplanetcenter.net/db_search/show_object?object_id=120347
|url-status = live
}}</ref>


<ref name="MPC-Circulars-Archive">{{cite web
<ref name="MPC-Circulars-Archive">{{cite web
|title = MPC/MPO/MPS Archive
|title = MPC/MPO/MPS Archive
|work = Minor Planet Center
|work = Minor Planet Center
|url = https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html
|url = https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html
|access-date = 3 April 2017}}</ref>
|access-date = 3 April 2017
|archive-date = 11 September 2019
|archive-url = https://web.archive.org/web/20190911230626/https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html
|url-status = live
}}</ref>


<ref name=TNOsCool8>
<ref name=TNOsCool8>
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|bibcode = 2012Icar..219..676S }}</ref>
|bibcode = 2012Icar..219..676S }}</ref>


<ref name="MPEC 2009-R09">
<ref name="MPEC 2009-R09">{{cite web
{{cite web
|title=MPEC 2009-R09 :Distant Minor Planets (2009 SEPT. 16.0 TT)
|title=MPEC 2009-R09 :Distant Minor Planets (2009 SEPT. 16.0 TT)
|date=2009-09-04
|date=2009-09-04
|publisher=[[IAU Minor Planet Center]]
|publisher=[[IAU Minor Planet Center]]
|url=https://www.minorplanetcenter.net/mpec/K09/K09R09.html
|url=https://www.minorplanetcenter.net/mpec/K09/K09R09.html
|access-date=2011-07-05}}</ref>
|access-date=2011-07-05
|archive-date=2018-10-02
|archive-url=https://web.archive.org/web/20181002022942/https://minorplanetcenter.net//mpec/K09/K09R09.html
|url-status=live
}}</ref>


<ref name=Buie>
<ref name=Buie>{{cite web
|author-link=Marc W. Buie
{{cite web
|author-link=Marc W. Buie|first=Marc W.|last=Buie
|first=Marc W.
|last=Buie
|type=2007-08-12 using 62 of 73 observations
|type=2007-08-12 using 62 of 73 observations
|title=Orbit Fit and Astrometric record for 120347
|title=Orbit Fit and Astrometric record for 120347
|publisher=SwRI (Space Science Department)
|publisher=SwRI (Space Science Department)
|url=http://www.boulder.swri.edu/~buie/kbo/astrom/120347.html
|url=http://www.boulder.swri.edu/~buie/kbo/astrom/120347.html
|access-date=2009-10-04}}</ref>
|access-date=2009-10-04
|archive-date=2012-03-09
|archive-url=https://web.archive.org/web/20120309113753/http://www.boulder.swri.edu/~buie/kbo/astrom/120347.html
|url-status=live
}}</ref>


<ref name="Brown-dplist">
<ref name="Brown-dplist">{{cite web
{{cite web
|title=How many dwarf planets are there in the outer solar system? (updates daily)
|title=How many dwarf planets are there in the outer solar system? (updates daily)
|publisher=[[California Institute of Technology]]
|publisher=[[California Institute of Technology]]
Line 172: Line 189:
|last=Brown
|last=Brown
|url=http://web.gps.caltech.edu/~mbrown/dps.html
|url=http://web.gps.caltech.edu/~mbrown/dps.html
|access-date=2016-11-29}}</ref>
|access-date=2016-11-29
|archive-date=2022-07-19
|archive-url=https://web.archive.org/web/20220719141419/http://web.gps.caltech.edu/~mbrown/dps.html
|url-status=live
}}</ref>


<ref name="Schaller2008">
<ref name="Schaller2008">
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|bibcode= 2008ApJ...684L.107S |doi= 10.1086/592232|s2cid=118487075}}</ref>
|bibcode= 2008ApJ...684L.107S |doi= 10.1086/592232|s2cid=118487075}}</ref>


<ref name=IAUC8751>
<ref name=IAUC8751>{{cite web
{{cite web
|url=http://www.cbat.eps.harvard.edu/iauc/08700/08751.html
|url=http://www.cbat.eps.harvard.edu/iauc/08700/08751.html
|title=IAUC 8751: (120347) 2004 SB_60; 2006gi, 2006gj; V733 Cep
|title=IAUC 8751: (120347) 2004 SB_60; 2006gi, 2006gj; V733 Cep
|publisher=Cbat.eps.harvard.edu
|publisher=Cbat.eps.harvard.edu
|access-date=2014-06-14}}</ref>
|access-date=2014-06-14
|archive-date=2013-12-03
|archive-url=https://web.archive.org/web/20131203012326/http://www.cbat.eps.harvard.edu/iauc/08700/08751.html
|url-status=live
}}</ref>


<ref name=Gladman-classification>
<ref name=Gladman-classification>{{cite book
{{cite book
|last1 = Gladman
|last1 = Gladman
|first1 = B.
|first1 = B.
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|date = 2008
|date = 2008
|chapter = Nomenclature in the Outer Solar System
|chapter = Nomenclature in the Outer Solar System
|chapter-url=http://www.lpi.usra.edu/books/ssbn2008/7002.pdf
|chapter-url = http://www.lpi.usra.edu/books/ssbn2008/7002.pdf
|title = The Solar System Beyond Neptune
|title = The Solar System Beyond Neptune
|page = 43}}</ref>
|page = 43
|access-date = 2016-05-01
|archive-date = 2012-11-02
|archive-url = https://web.archive.org/web/20121102205338/http://www.lpi.usra.edu/books/ssbn2008/7002.pdf
|url-status = live
}}</ref>


<ref name="Belskaya2015">{{cite journal
<ref name="Belskaya2015">{{cite journal
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|url=http://journals.cambridge.org/article_S1743921310001717
|url=http://journals.cambridge.org/article_S1743921310001717
|access-date=17 January 2012}}</ref>
|access-date=17 January 2012}}</ref>

-->
-->

<ref name="Cook2023">{{cite conference
|display-authors = etal
|first1 = J. C.
|last1 = Cook
|first2 = R.
|last2 = Brunetto
|first3 = A. C.
|last3 = De Souza Feliciano
|first4 = J.
|last4 = Emery
|first5 = B.
|last5 = Holler
|first6 = A. H.
|last6 = Parker
|title = Hapke Modeling of Several KBOs from JWST Observations
|url = https://www.hou.usra.edu/meetings/acm2023/pdf/2526.pdf
|conference = Asteroids, Comets, Meteors Conference 2023
|publisher = Lunar and Planetary Institute
|issue = 2851
|date = June 2023
|access-date = 2023-05-24
|archive-date = 2023-05-24
|archive-url = https://web.archive.org/web/20230524001156/https://www.hou.usra.edu/meetings/acm2023/pdf/2526.pdf
|url-status = live
}}</ref>


}} <!-- end of refs -->
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{{Trans-Neptunian objects}}
{{Trans-Neptunian objects}}
{{Solar System moons (compact)}}
{{Solar System moons (compact)}}
{{Authority control}}


{{DEFAULTSORT:Salacia}}
{{DEFAULTSORT:Salacia}}

Latest revision as of 11:46, 30 October 2024

120347 Salacia
Keck Telescope image of Salacia (bright, center) and its moon Actaea (faint, at left)
Discovery[1][2]
Discovered byH. G. Roe
M. E. Brown
K. M. Barkume
Discovery sitePalomar Obs.
Discovery date22 September 2004
Designations
(120347) Salacia
Pronunciation/səˈleɪʃə/ (sə-LAY-shə)
Named after
Salacia (Roman mythology)[2]
2004 SB60
TNO[1] · Cubewano[3]
Extended[4]
AdjectivesSalacian
Symbol or (rare)
Orbital characteristics[1]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 3
Observation arc37.16 yr (13,572 days)
Earliest precovery date25 July 1982
Aphelion46.670 AU
Perihelion37.697 AU
42.184 AU
Eccentricity0.10636
273.98 yr (100,073 days)
123.138°
0° 0m 12.951s / day
Inclination23.921°
279.880°
312.294°
Known satellites1 (Actaea)
Physical characteristics
846±21 km[5][a]
866±37 km[6]
Mass(4.922±0.071)×1020 kg (system)[5]
Mean density
1.5±0.12 g/cm3[5]
1.26±0.16 g/cm3[6]
6.09 h (0.254 d)
6.09 h[1]
0.042±0.004[6]
BB[7]
B−V=0.66±0.06[7]
V−R=0.40±0.04[7]
V−I=0.83±0.04[7]
20.7
4.360±0.011 (system)[8]
4.476±0.013 (Salacia)[8]
6.850±0.053 (Actaea)[8]
3.9[1]

Salacia (minor-planet designation: 120347 Salacia) is a large trans-Neptunian object (TNO) in the Kuiper belt, approximately 850 km (530 mi) in diameter. It was discovered on 22 September 2004, by American astronomers Henry Roe, Michael Brown and Kristina Barkume at the Palomar Observatory in California, United States. Salacia orbits the Sun at an average distance that is slightly greater than that of Pluto. It was named after the Roman goddess Salacia and has a single known moon, Actaea.

Brown estimated that Salacia is nearly certainly a dwarf planet.[9] However, William Grundy et al. argue that objects in the size range of 400–1,000 km, with densities of ≈ 1.2 g/cm3 or less and albedos less than ≈ 0.2, have likely never compressed into fully solid bodies or been resurfaced, let alone differentiated or collapsed into hydrostatic equilibrium, and so are highly unlikely to be dwarf planets.[10] Salacia is at the upper end of this size range and has a very low albedo, though Grundy et al. later found it to have the relatively high density of 1.5±0.1 g/cm3.[5]

Orbit

[edit]
The orbit of Salacia is similar to Pluto's, except for a near opposite longitude of ascending node. Its current position is near its most northern position above the ecliptic.

Salacia is a non-resonant object with a moderate eccentricity (0.11) and large inclination (23.9°), making it a scattered–extended object in the classification of the Deep Ecliptic Survey and a hot classical Kuiper belt object in the classification system of Gladman et al.,[11] which may be the same thing if they are part of a single population that formed during the outward migration of Neptune.[8] Salacia's orbit is within the parameter space of the Haumea collisional family, but Salacia is not part of it, as evidenced by its lack of the strong water-ice absorption bands.[8]

Physical characteristics

[edit]

As of 2019, the total mass of the Salacia–Actaea system is estimated at (4.922±0.071)×1020 kg, with an average system density of 1.51 g/cm3; Salacia itself is estimated to be around 846 km in diameter.[5] Salacia has the lowest albedo of any known large trans-Neptunian object.[8] According to the estimate from 2017 based on an improved thermophysical modelling, the size of Salacia is slightly larger at 866 km and its density therefore slightly lower (calculated at 1.26 g/cm3 with the old mass estimate discussed below).[6]

Salacia was previously believed to have a mass of around (4.38±0.16)×1020 kg, in which case it would also have had the lowest density (around 1.29 g/cm3) of any known large TNO;[12] William Grundy and colleagues proposed that this low density would imply that Salacia never collapsed into a solid body, in which case it would not be in hydrostatic equilibrium.[10] Salacia's infrared spectrum is almost featureless, indicating an abundance of water ice of less than 5% on the surface.[12][13] Near-infrared spectroscopy by the James Webb Space Telescope (JWST) in 2022 revealed the presence of water ice in Salacia's surface.[14] No signs of volatile ices such as methane were detected in JWST's spectrum of Salacia.[14] Its light-curve amplitude is only 3%.[8]

Satellite

[edit]
Main article: Actaea (moon)

Salacia has one known natural satellite, Actaea, that orbits its primary every 5.49380±0.00016 d at a distance of 5619±89 km and with an eccentricity of 0.0084±0.0076. It was discovered on 21 July 2006 by Keith Noll, Harold Levison, Denise Stephens and William Grundy with the Hubble Space Telescope.[15]

Actaea is 2.372±0.060 magnitudes fainter than Salacia,[12] implying a diameter ratio of 2.98 for equal albedos.[8] Hence, assuming equal albedos, it has a diameter of 286±24 km[12] According to the estimate from 2017 based on an improved modelling, the size of Actaea is slightly larger at 290±21 km.[6]

Actaea has the same color as Salacia (V−I = 0.89±0.02 and 0.87±0.01, respectively), supporting the assumption of equal albedos.[8]

It has been calculated that the Salacia system should have undergone enough tidal evolution to circularize their orbits, which is consistent with the low measured eccentricity, but that the primary need not be tidally locked.[8] The ratio of its semi-major axis to its primary's Hill radius is 0.0023, the tightest trans-Neptunian binary with a known orbit.[8] Salacia and Actaea will next occult each other in 2067.[8]

Name

[edit]

This minor planet was named after Salacia (/səˈleɪʃə/), the goddess of salt water and the wife of Neptune.[2] The naming citation was published on 18 February 2011 (M.P.C. 73984).[16]

The moon's name, Actaea /ækˈtiːə/, was assigned on the same date. Actaea is a nereid or sea nymph.

Planetary symbols are no longer used much in astronomy, so Salacia never received a symbol in the astronomical literature. Denis Moskowitz, a software engineer who designed most of the dwarf planet symbols, proposed a stylised hippocamp (, formerly ) as the symbol for Salacia;[17][18] this symbol is not widely used.

See also

[edit]

Notes

[edit]
  1. ^ approximation if Salacia and Actaea were both spherical and had the same albedo

References

[edit]
EarthMoonCharonCharonNixNixKerberosKerberosStyxStyxHydraHydraPlutoPlutoDysnomiaDysnomiaErisErisNamakaNamakaHi'iakaHi'iakaHaumeaHaumeaMakemakeMakemakeMK2MK2XiangliuXiangliuGonggongGonggongWeywotWeywotQuaoarQuaoarSednaSednaVanthVanthOrcusOrcusActaeaActaeaSalaciaSalacia2002 MS42002 MS4File:10 Largest Trans-Neptunian objects (TNOS).png
Artistic comparison of Pluto, Eris, Makemake, Haumea, Gonggong (2007 OR10), Sedna, Quaoar, Orcus, 2002 MS4, and Salacia.
  1. ^ a b c d e "JPL Small-Body Database Browser: 120347 Salacia (2004 SB60)" (2019-09-21 last obs.). Jet Propulsion Laboratory. 7 November 2019. Archived from the original on 3 April 2017. Retrieved 20 February 2020.
  2. ^ a b c "120347 Salacia (2004 SB60)". Minor Planet Center. Archived from the original on 3 April 2017. Retrieved 22 July 2018.
  3. ^ "MPEC 2009-R09 :Distant Minor Planets (2009 SEPT. 16.0 TT)". IAU Minor Planet Center. 2009-09-04. Archived from the original on 2018-10-02. Retrieved 2011-07-05.
  4. ^ Buie, Marc W. "Orbit Fit and Astrometric record for 120347" (2007-08-12 using 62 of 73 observations). SwRI (Space Science Department). Archived from the original on 2012-03-09. Retrieved 2009-10-04.
  5. ^ a b c d e Grundy, W. M.; Noll, K. S.; Roe, H. G.; Buie, M. W.; Porter, S. B.; Parker, A. H.; Nesvorný, D.; Benecchi, S. D.; Stephens, D. C.; Trujillo, C. A. (2019). "Mutual Orbit Orientations of Transneptunian Binaries" (PDF). Icarus. 334: 62–78. Bibcode:2019Icar..334...62G. doi:10.1016/j.icarus.2019.03.035. ISSN 0019-1035. S2CID 133585837. Archived from the original (PDF) on 2020-01-15. Retrieved 2019-10-26.
  6. ^ a b c d e Brown, Michael E.; Butler, Bryan J. (20 June 2017). "The Density of Mid-sized Kuiper Belt Objects from ALMA Thermal Observations". The Astronomical Journal. 154 (1): 19. arXiv:1702.07414. Bibcode:2017AJ....154...19B. doi:10.3847/1538-3881/aa6346.
  7. ^ a b c d Belskaya, Irina N.; Barucci, Maria A.; Fulchignoni, Marcello; Lazzarin, M. (April 2015). "Updated taxonomy of trans-neptunian objects and centaurs: Influence of albedo". Icarus. 250: 482–491. Bibcode:2015Icar..250..482B. doi:10.1016/j.icarus.2014.12.004.
  8. ^ a b c d e f g h i j k l Stansberry, J.A.; Grundy, W.M.; Mueller, M.; et al. (2012). "Physical Properties of Trans-Neptunian Binaries (120347) Salacia–Actaea and (42355) Typhon–Echidna". Icarus. 219 (2): 676–688. Bibcode:2012Icar..219..676S. CiteSeerX 10.1.1.398.6675. doi:10.1016/j.icarus.2012.03.029.
  9. ^ Brown, Michael E. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Archived from the original on 2022-07-19. Retrieved 2016-11-29.
  10. ^ a b W.M. Grundy, K.S. Noll, M.W. Buie, S.D. Benecchi, D. Ragozzine & H.G. Roe, 'The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ((229762) 2007 UK126)', Icarus (forthcoming, available online 30 March 2019) Archived 7 April 2019 at the Wayback Machine DOI: 10.1016/j.icarus.2018.12.037,
  11. ^ Gladman, B.; Marsden, B. G.; VanLaerhoven, C. (2008). "Nomenclature in the Outer Solar System" (PDF). The Solar System Beyond Neptune. p. 43. Archived (PDF) from the original on 2012-11-02. Retrieved 2016-05-01.
  12. ^ a b c d Fornasier, S.; Lellouch, E.; Müller, P., T.; et al. (2013). "TNOs are Cool: A survey of the trans-Neptunian region. VIII. Combined Herschel PACS and SPIRE observations of 9 bright targets at 70–500 μm". Astronomy & Astrophysics. 555: A92. arXiv:1305.0449v2. Bibcode:2013A&A...555A..15F. doi:10.1051/0004-6361/201321329. S2CID 119261700.
  13. ^ Schaller, E. L.; Brown, M. E. (2008). "Detection of Additional Members of the 2003 EL61 Collisional Family via Near-Infrared Spectroscopy". Astrophysical Journal. 684 (2): L107–L109. arXiv:0808.0185. Bibcode:2008ApJ...684L.107S. doi:10.1086/592232. S2CID 118487075.
  14. ^ a b Cook, J. C.; Brunetto, R.; De Souza Feliciano, A. C.; Emery, J.; Holler, B.; Parker, A. H.; et al. (June 2023). Hapke Modeling of Several KBOs from JWST Observations (PDF). Asteroids, Comets, Meteors Conference 2023. Lunar and Planetary Institute. Archived (PDF) from the original on 2023-05-24. Retrieved 2023-05-24.
  15. ^ "IAUC 8751: (120347) 2004 SB_60; 2006gi, 2006gj; V733 Cep". Cbat.eps.harvard.edu. Archived from the original on 2013-12-03. Retrieved 2014-06-14.
  16. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Archived from the original on 11 September 2019. Retrieved 3 April 2017.
  17. ^ Miller, Kirk (26 October 2021). "Unicode request for dwarf-planet symbols" (PDF). unicode.org. Archived (PDF) from the original on 23 March 2022. Retrieved 18 October 2022.
  18. ^ Miller, Kirk (18 October 2024). "Preliminary presentation of constellation symbols" (PDF). unicode.org. The Unicode Consortium. Retrieved 22 October 2024.
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