Editing Sedna (dwarf planet) (section)

{{Short description|Distant, small body in the Solar System}}
{{Featured article}}
{{Use American English|date=August 2024}}
{{Use dmy dates|date=August 2024}}
{{Infobox planet
| minorplanet = yes
| background = #C2E0FF
| name = 90377 Sedna
| symbol = [[File:Sedna symbol (bold).svg|24px|⯲]] (mostly astrological)
| image = Sedna PRC2004-14d.jpg
| image_scale = 
| image_alt = Single fuzzy white dot with lots of background noise
| caption = Low-resolution image of Sedna by the [[Hubble Space Telescope]], March 2004
| discovery_ref = <ref name="discovery" />
| discoverer = [[Michael E. Brown|Michael Brown]]<br />[[Chad Trujillo]]<br />[[David L. Rabinowitz|David Rabinowitz]]
| discovery_site = [[Samuel Oschin Telescope]]
| discovered = 14 November 2003
| mpc_name = (90377) Sedna
| pronounced = {{IPAc-en|ˈ|s|ɛ|d|n|ə}}
| adjective = Sednian<ref name="sednian"/>
| alt_names = {{mp|2003 [[Van Biesbroeck's star catalog | VB]]|12}}
| named_after = [[Sedna (mythology)|Sedna]] ([[Inuit]] goddess of sea and marine animals)
| mp_category = [[trans-Neptunian object|TNO]]<ref name="jpldata" />{{·}}[[Detached object|detached]]<br />[[sednoid]]<ref name="DES" /> [[dwarf planet]]
| orbit_ref = <ref name="jpldata" />
| barycentric = yes
| epoch = 31 May 2020 ([[Julian day|JD]] 2458900.5)
| uncertainty = 2
| observation_arc = 30 years
| earliest_precovery_date = 25 September 1990
| semimajor = {{convert|506|AU|e9km|abbr=unit|sigfig=2}}<ref name="barycenter"/> or 0.007 ly
| perihelion = {{convert|76.19|AU|e9km|abbr=unit|sigfig=3}}<ref name="Perihelion2076"/><ref name="barycenter"/><ref name="AstDyS2076" />
| time_periastron = ≈ 18 July 2076<ref name="Perihelion2076"/><ref name="AstDyS2076" />
| aphelion = {{convert|937|AU|e9km|abbr=unit|lk=on|sigfig=2}}<ref name="barycenter"/><ref group=lower-alpha name=footnoteG/>
| eccentricity = 0.8496<ref name="barycenter"/>
| period = {{val|11390}} [[Julian year (astronomy)|yr]] (barycentric)<ref group=lower-alpha name=footnoteG/>
| synodic_period = 11,408 Gregorian years
| inclination = 11.9307[[degree (angle)|°]]
| asc_node = 144.248°
| arg_peri = 311.352°
| mean_anomaly = 358.117°
| mean_motion = {{Deg2DMS|0.00008020|sup=ms}} / day
| avg_speed = 1.04&nbsp;km/[[second|s]]
| mean_diameter = {{val|906|314|258|u=km}}<ref name="Lellouch A60">{{Cite journal |last1=Lellouch |first1=E. |last2=Santos-Sanz |first2=P. |last3=Lacerda |first3=P. |last4=Mommert |first4=M. |last5=Duffard |first5=R. |last6=Ortiz |first6=J. L. |last7=Müller |first7=T. G. |last8=Fornasier |first8=S. |last9=Stansberry |first9=J. |last10=Kiss |first10=Cs. |last11=Vilenius |first11=E. |last12=Mueller |first12=M. |last13=Peixinho |first13=N. |last14=Moreno |first14=R. |last15=Groussin |first15=O. |date=29 September 2013 |title="TNOs are Cool": A survey of the trans-Neptunian region: IX. Thermal properties of Kuiper belt objects and Centaurs from combined Herschel and Spitzer observations⋆⋆⋆ |journal=Astronomy & Astrophysics |volume=557 |pages=A60 |doi=10.1051/0004-6361/201322047 |issn=0004-6361|doi-access=free |bibcode=2013A&A...557A..60L |hdl=10316/80307 |hdl-access=free }}</ref><br />{{val|1025|135|u=km|p=>&nbsp;}}<br />(occultation chord)<ref name="Rommel2020"/>
| mass = 
| density = 
| surface_grav =
| escape_velocity = 
| rotation = {{val|10.273|0.002}} [[Hour|h]]<br />(~18 h less likely)<ref name="Gaudi2005" />
| spectral_type = ([[Trans-Neptunian object#Colors|red]]) {{nowrap|1=B−V=1.24}}; {{nowrap|1=V−R=0.78}}<ref name="Tegler" />
| magnitude = 20.8 (opposition)<ref name="AstDys" /><br />20.5&nbsp;([[apsis|perihelic]])<ref name="Horizons2076" />
| abs_magnitude = {{val|1.83|0.05}}<ref name=herschel /><br />1.3<ref name="jpldata" />
| albedo = {{val|0.410|0.393|0.186}}<ref name="Lellouch A60">{{Cite journal |last1=Lellouch |first1=E. |last2=Santos-Sanz |first2=P. |last3=Lacerda |first3=P. |last4=Mommert |first4=M. |last5=Duffard |first5=R. |last6=Ortiz |first6=J. L. |last7=Müller |first7=T. G. |last8=Fornasier |first8=S. |last9=Stansberry |first9=J. |last10=Kiss |first10=Cs. |last11=Vilenius |first11=E. |last12=Mueller |first12=M. |last13=Peixinho |first13=N. |last14=Moreno |first14=R. |last15=Groussin |first15=O. |date=29 September 2013 |title="TNOs are Cool": A survey of the trans-Neptunian region: IX. Thermal properties of Kuiper belt objects and Centaurs from combined Herschel and Spitzer observations⋆⋆⋆ |journal=Astronomy & Astrophysics |volume=557 |pages=A60 |doi=10.1051/0004-6361/201322047 |issn=0004-6361|doi-access=free |bibcode=2013A&A...557A..60L |hdl=10316/80307 |hdl-access=free }}</ref>
| single_temperature = ≈ 12 [[Kelvin|K]]&nbsp;''(see [[list of Solar System objects in hydrostatic equilibrium#Manual calculations (unless otherwise cited)|note]])''
}}

'''Sedna''' ([[minor-planet designation]]: '''90377 Sedna''') is a [[dwarf planet]] in the outermost reaches of the [[Solar System]], orbiting the [[Sun]] far beyond the [[Neptune#Orbit_and_rotation|orbit of Neptune]]. Discovered in 2003, the frigid planetoid is one of the [[Trans-Neptunian object#Colors|reddest]] known among Solar System bodies. Detailed [[Spectroscopy|spectroscopic]] analysis has revealed Sedna's surface to be a mixture of the solid [[Ice|ices]] of [[Ice|water]] (H<sub>2</sub>O),<ref name=":1">{{Cite journal |last1=Emery |first1=J. P. |last2=Wong |first2=I. |last3=Brunetto |first3=R. |last4=Cook |first4=J. C. |last5=Pinilla-Alonso |first5=N. |last6=Stansberry |first6=J. A. |last7=Holler |first7=B. J. |last8=Grundy |first8=W. M. |last9=Protopapa |first9=S. |last10=Souza-Feliciano |first10=A. C. |last11=Fernández-Valenzuela |first11=E. |last12=Lunine |first12=J. I. |last13=Hines |first13=D. C. |date=15 May 2024 |title=A tale of 3 dwarf planets: Ices and organics on Sedna, Gonggong, and Quaoar from JWST spectroscopy |journal=Icarus |volume=414 |pages=116017 |doi=10.1016/j.icarus.2024.116017 |issn=0019-1035 |quote=Sedna’s relatively high visible-wavelength geometric albedo of 0.32 (which suggests a NIR geometric albedo close to or exceeding 1.0) indicates an ice-rich surface, despite the clear spectral signatures of complex organic molecules. |doi-access=free|bibcode=2024Icar..41416017E |arxiv=2309.15230 }}</ref> [[carbon dioxide]] (CO<sub>2</sub>), and [[Methane clathrate|ethane]] (C<sub>2</sub>H<sub>6</sub>), along with occasional sedimentary deposits of [[methane]] (CH<sub>4</sub>)-derived,<ref>{{Cite journal |last1=Zubko |first1=V. A. |last2=Sukhanov |first2=A. A. |last3=Fedyaev |first3=K. S. |last4=Koryanov |first4=V. V. |last5=Belyaev |first5=A. A. |date=1 October 2021 |title=Analysis of mission opportunities to Sedna in 2029–2034 |url=https://www.sciencedirect.com/science/article/abs/pii/S0273117721004555 |journal=Advances in Space Research |volume=68 |issue=7 |pages=2752–2775 |doi=10.1016/j.asr.2021.05.035 |arxiv=2112.13017 |bibcode=2021AdSpR..68.2752Z |issn=0273-1177 |quote=...As estimated in (Trujillo et al., 2005, Barucci et al., 2005, Emery et al., 2007, Pál et al., 2012, Trujillo and Sheppard, 2014), the object has a layer of hydrocarbon sediment produced by irradiated methane. The existence of the hydrocarbon sediment may be a reason why the Sedna’s surface is a bright red shade (Cuk, 2004, Sheppard, 2010).... |via=Elsevier Science Direct}}</ref> vividly reddish-colored organic [[tholin]]s,<ref name=":1" /> a surface chemical makeup somewhat similar to those of other [[trans-Neptunian objects]].<ref>{{Cite journal |last1=Emery |first1=J. P. |last2=Wong |first2=I. |last3=Brunetto |first3=R. |last4=Cook |first4=J. C. |last5=Pinilla-Alonso |first5=N. |last6=Stansberry |first6=J. A. |last7=Holler |first7=B. J. |last8=Grundy |first8=W. M. |last9=Protopapa |first9=S. |last10=Souza-Feliciano |first10=A. C. |last11=Fernández-Valenzuela |first11=E. |last12=Lunine |first12=J. I. |last13=Hines |first13=D. C. |date=15 May 2024 |title=A tale of 3 dwarf planets: Ices and organics on Sedna, Gonggong, and Quaoar from JWST spectroscopy |url=https://www.sciencedirect.com/science/article/pii/S0019103524000769 |journal=Icarus |volume=414 |pages=116017 |doi=10.1016/j.icarus.2024.116017 |bibcode=2024Icar..41416017E |issn=0019-1035 |quote=Spectra of all three objects show steep red spectral slopes and strong, broad absorptions between 2.7 and 3.6 μm indicative of complex organic molecules......These differences of Sedna, Gonggong, and Quaoar from the smaller KBO population supports the inference of different evolutionary history based on their size.|arxiv=2309.15230 }}</ref> Sedna has no detectable [[atmosphere]], as its temperature is far too low for solids to [[Sublimation (phase transition)|volatilize]].<ref>{{Cite journal |last1=Emery |first1=J. P. |last2=Wong |first2=I. |last3=Brunetto |first3=R. |last4=Cook |first4=J. C. |last5=Pinilla-Alonso |first5=N. |last6=Stansberry |first6=J. A. |last7=Holler |first7=B. J. |last8=Grundy |first8=W. M. |last9=Protopapa |first9=S. |last10=Souza-Feliciano |first10=A. C. |last11=Fernández-Valenzuela |first11=E. |last12=Lunine |first12=J. I. |last13=Hines |first13=D. C. |date=15 May 2024 |title=A tale of 3 dwarf planets: Ices and organics on Sedna, Gonggong, and Quaoar from JWST spectroscopy |url=https://www.sciencedirect.com/science/article/pii/S0019103524000769 |journal=Icarus |volume=414 |doi=10.1016/j.icarus.2024.116017 |bibcode=2024Icar..41416017E |issn=0019-1035 |quote=...Sedna is not expected to support an atmosphere at its great distances... |via=Elsevier Science Direct|arxiv=2309.15230 }}</ref> Within range of uncertainty, it is tied with the dwarf planet {{dp|Ceres}} in the [[asteroid belt]] as the [[List of Solar System objects by size|largest dwarf planet]] not known to have a [[Natural satellite|moon]]. With a diameter of roughly 1,000&nbsp;km,<ref>{{Cite journal |last1=Bettati |first1=Amelia |last2=Lunine |first2=Jonathan |date=1 April 2025 |title=Atmospheric escape explains diverse surface compositions of Pluto vs Sedna |journal=Icarus |volume=430 |page=1 |doi=10.1016/j.icarus.2025.116482 |issn=0019-1035 |quote=...Although the radius is also uncertain, we minimize the number of cases by taking an average radius of 1000 km for Sedna... |doi-access=free |bibcode=2025Icar..43016482B }}</ref> it is nearly the size of [[Tethys (moon)|Tethys]] around [[Saturn]]. Owing to its lack of known moons,<ref>{{Cite journal |last1=Bettati |first1=Amelia |last2=Lunine |first2=Jonathan |date=1 April 2025 |title=Atmospheric escape explains diverse surface compositions of Pluto vs Sedna |journal=Icarus |volume=430 |page=12 |doi=10.1016/j.icarus.2025.116482 |issn=0019-1035 |quote=...No moon has been detected around Sedna, so it is not yet possible to calculate its density,... |doi-access=free |bibcode=2025Icar..43016482B }}</ref> the [[Kepler's laws of planetary motion|Keplerian laws]] of planetary motion cannot be utilized for determining its mass, and the actual figure remains as yet unknown.

Sedna's orbit is [[List of Solar System objects most distant from the Sun|one of the widest known]] in the Solar System. Its [[apsis|aphelion]], the farthest point from the Sun in its orbit, is located 937&nbsp;[[astronomical unit]]s (AU) away.<ref name="barycenter"/> This is some 19 times that of [[Pluto]], leading to it spending most of its time well beyond the [[Heliopause (astronomy)|heliopause]] (120 AU),<ref>{{Cite journal |last1=Emery |first1=J. P. |last2=Wong |first2=I. |last3=Brunetto |first3=R. |last4=Cook |first4=J. C. |last5=Pinilla-Alonso |first5=N. |last6=Stansberry |first6=J. A. |last7=Holler |first7=B. J. |last8=Grundy |first8=W. M. |last9=Protopapa |first9=S. |last10=Souza-Feliciano |first10=A. C. |last11=Fernández-Valenzuela |first11=E. |last12=Lunine |first12=J. I. |last13=Hines |first13=D. C. |date=15 May 2024 |title=A tale of 3 dwarf planets: Ices and organics on Sedna, Gonggong, and Quaoar from JWST spectroscopy |journal=Icarus |volume=414 |page=12, right paragraph 3 |doi=10.1016/j.icarus.2024.116017 |issn=0019-1035 |quote=...Sedna spends most of its time outside of the heliopause (at ~120 AU; e.g., Stone et al., 2013, 2019),... |doi-access=free|bibcode=2024Icar..41416017E |arxiv=2309.15230 }}</ref> the boundary beyond which the influences of particles from [[interstellar space]] dominate those from the Sun. Sedna's orbit is also one of the most elliptical and narrow discovered, with an [[Orbital eccentricity|eccentricity]] of 0.8496. This implies that its [[perihelion]], or point of closest approach to the Sun, at 76 AU is around 12.3 times as close as its aphelion. {{As of|2025|February}}, Sedna is {{convert|83.20|AU|e9km|abbr=unit|lk=out|sigfig=4}} from the Sun,<ref>{{Cite web |title=Asteroid 90377 Sedna (2003 VB12) {{!}} TheSkyLive |url=https://theskylive.com/sedna-info |access-date=15 February 2025 |website=theskylive.com}}</ref> approaching perihelion at ~4.4 km/s,<ref>Conservation of specific kinetic + potential energy, with Sun's gravitational parameter substituted.

<math>\frac{1.327 \cdot 10^{20}}{1.495 \cdot 10^{8}} \, \left(\frac{1}{83.2} - \frac{1}{937}\right) = \frac{1}{2} \, \left(x^{2} - 377^{2}\right)</math></ref> and 2.5 times as far away as [[Neptune]]. The dwarf planets {{dp|Eris}} and {{dp|Gonggong}} are presently farther away from the Sun.  A [[Interplanetary spaceflight#Launch windows|transfer window]] for a probe [[Flyby (spaceflight)#Kuiper belt|fly-by]] in 2029 utilizing a [[Gravity assist|gravitational assist]] from [[Jupiter]] was proposed, taking 25 years to travel to the dwarf planet, 80 AU (12 billion kilometers) distant.<ref>{{Cite journal |last1=Zubko |first1=V. A. |last2=Sukhanov |first2=A. A. |last3=Fedyaev |first3=K. S. |last4=Koryanov |first4=V. V. |last5=Belyaev |first5=A. A. |date=1 October 2021 |title=Analysis of mission opportunities to Sedna in 2029–2034 |url=https://www.sciencedirect.com/science/article/abs/pii/S0273117721004555 |journal=Advances in Space Research |volume=68 |issue=7 |pages=2752–2775 |doi=10.1016/j.asr.2021.05.035 |arxiv=2112.13017 |bibcode=2021AdSpR..68.2752Z |issn=0273-1177 |quote=...Results of the research presented in this article show that the launch in 2029 provides the best transfer conditions in terms of minimum total characteristic velocity... |via=Elsevier Science Direct}}</ref>

Due to its exceptionally [[Flattening|elongated]] orbit, the dwarf planet takes approximately 11,400 years to return to the same point in its orbit around the Sun. The [[International Astronomical Union]] (IAU) initially classified Sedna as a member of the [[scattered disc]], a group of objects sent into high-eccentricity orbits by the gravitational influence of [[Neptune]]. However, several astronomers who worked in the associated field contested this classification as even its perihelion is far too distant for it to have been scattered by any of the currently known planets. This has led some astronomers to informally refer to it as the first known member of the [[Hills cloud|inner Oort cloud]]. The dwarf planet is also the prototype of a new orbit class of objects named after itself, the [[sednoid]]s, which include {{mpl|2012 VP|113}} and [[541132 Leleākūhonua|Leleākūhonua]], both celestial bodies with large perihelion distances and high eccentricities.<ref>{{Cite journal |last1=Huang |first1=Yukun |last2=Gladman |first2=Brett |date=15 February 2024 |title=Primordial Orbital Alignment of Sednoids |journal=The Astrophysical Journal Letters |language=en |volume=962 |issue=2 |pages=L33 |doi=10.3847/2041-8213/ad2686 |doi-access=free |arxiv=2310.20614 |bibcode=2024ApJ...962L..33H |issn=2041-8205 |quote=We examined the past history of the three most detached trans-Neptunian objects (TNOs)—Sedna, 2012 VP113, and Leleakuhonua (2015 TG387)—the three clearest members of the dynamical class known as sednoids, with high perihelia distances q... }}</ref>

The astronomer [[Michael E. Brown]], co-discoverer of Sedna, has argued that its unusual orbit could provide information on the early evolution of the Solar System.<ref name="fussman"/><ref name=Chang_2016/> Sedna might have been [[Perturbation (astronomy)|perturbed]] into its orbit by a star  within the Sun's [[Open cluster|birth cluster]], or captured from a nearby wandering star, or have been sent into its present orbit through a close gravitational encounter with the hypothetical [[Planet Nine|9th planet]], sometime during the solar system's formation.<ref>{{Cite journal |last1=Zubko |first1=V. A. |last2=Sukhanov |first2=A. A. |last3=Fedyaev |first3=K. S. |last4=Koryanov |first4=V. V. |last5=Belyaev |first5=A. A. |date=1 October 2021 |title=Analysis of mission opportunities to Sedna in 2029–2034 |url=https://www.sciencedirect.com/science/article/abs/pii/S0273117721004555 |journal=Advances in Space Research |volume=68 |issue=7 |pages=2752–2775 |doi=10.1016/j.asr.2021.05.035 |arxiv=2112.13017 |bibcode=2021AdSpR..68.2752Z |issn=0273-1177 |quote=The discoverers (Brown et al., 2004) have supposed that Sedna was created in the Solar System at the early stage of its evolution, and its orbit was changed because of dynamic effects that followed the Sun’s formation within a dense stellar cluster (Brown et al., 2004, Morbidelli and Levison, 2004, Kenyon and Bromley, 2004, Adams, 2010, Kaib et al., 2011, Brasser and Schwamb, 2015). According to other versions, Sedna’s orbit was changed by a stellar encounter (Kaib and Quinn, 2008) (e.g., the passing Scholz’s star about 70 thousand years ago (Mamajek et al., 2015) at a distance of 52 thousand au from the Sun), or Sedna was captured from a low-mass star or a brown dwarf in interstellar space (Morbidelli and Levison, 2004). |via=Elsevier Science Direct}}</ref> The statistically unusual clustering to one side of the solar system of the aphelions of Sedna and other similar objects is speculated to be the evidence for the existence of a [[planets beyond Neptune|planet beyond the orbit of Neptune]],<ref>{{Cite journal |last1=Batygin |first1=Konstantin |last2=Brown |first2=Michael E. |title=Evidence for a Distant Giant Planet in the Solar System |journal=[[The Astronomical Journal]] |language=en |publication-place=Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA |publication-date=20 January 2016 |volume=151 |issue=2 |page=22 |doi=10.3847/0004-6256/151/2/22 |quote=ABSTRACT Recent analyses have shown that distant orbits within the scattered disk population of the Kuiper Belt exhibit an unexpected clustering in their respective arguments of perihelion....In this work we show that the orbits of distant Kuiper Belt objects (KBOs) cluster not only in argument of perihelion, but also in physical space. We demonstrate that the perihelion positions and orbital planes of the objects are tightly confined and that such a clustering has only a probability of 0.007% to be due to chance....can be maintained by a distant eccentric planet with mass 10 m⊕ .... whose perihelion is 180° away from the perihelia of the minor bodies....Continued analysis ....provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet. |postscript=This is THE paper. The paper that started everything, that which set things in motions unpredictable. |doi-access=free|bibcode=2016AJ....151...22B |arxiv=1601.05438 }}</ref> which would by itself orbit on the opposing side of the Sun.<ref name="Mike"/><ref name=Lakdawalla_2014/><ref name="Evidence for a Distant Giant Planet"/>