90377 Sedna

Infobox Planet
bgcolour=#FFFFC0
name=90377 Sedna


caption= Sedna is located in the center of the green circle
discovery=yes
discovery_ref=cite web
title=Discovery Circumstances: Numbered Minor Planets (90001)-(95000)
publisher=IAU: Minor Planet Center
url=http://www.cfa.harvard.edu/iau/lists/NumberedMPs090001.html
accessdate=2008-07-23 ]
discoverer=M. Brown, C. Trujillo, D. Rabinowitz
discovered=November 14, 2003
mp_name=90377 Sedna
alt_names=mp|2003 VB|12
mp_category=Trans-Neptunian object
detached object
orbit_ref =cite web
author=Marc W. Buie
date=2007-08-13
title=Orbit Fit and Astrometric record for 90377
publisher=Deep Ecliptic Survey
url=http://www.boulder.swri.edu/~buie/kbo/astrom/90377.html
accessdate=2006-01-17]
epoch=September 26, 1990 (JD 2 448 160.5)
semimajor=7.866 8×10¹³ m (525.86 AU)
perihelion=1.139 3e|13 m (76.156 AU)
aphelion=1.459e|14 m (975.56 AU)
eccentricity=0.855
period=around 4 404 480 d (12 059.06 a)
inclination=11.934°
asc_node=144.514°
arg_peri=311.123°
mean_anomaly=357.457°
avg_speed=1.04 km/s
physical_characteristics=yes
dimensions=1200–1600 kmcite web
title=The largest Kuiper belt objects
author=Michael E. Brown |work=CalTech
url=http://www.gps.caltech.edu/~mbrown/papers/ps/kbochap.pdf
accessdate=2008-09-19]
<1600 kmcite web
title=Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope
author=John Stansberry, Will Grundy, Mike Brown, Dale Cruikshank, John Spencer, David Trilling, Jean-Luc Margot
work=University of Arizona, Lowell Observatory, California Institute of Technology, NASA Ames Research Center, Southwest Research Institute, Cornell University
url=http://arxiv.org/abs/astro-ph/0702538v2
year=2007
accessdate=2008-07-27]
mass=8.3e|20&ndash;7.0e|21 kg [Radius of 590 km and density of 0.97 = 8.3e|20 kg mass. Radius of 900 km and density of 2.3 = 7.0e|21 kg mass]
(0.05&ndash;0.42 Eris)
density=2.0? g/cm³
surface_grav=0.33–0.50 m/s²
escape_velocity=0.62–0.95 km/s
sidereal_day=0.42 d (10 h) [http://cfa-www.harvard.edu/press/pr0510.html ¹]
spectral_type= (red) B-V=1.24; V-R=0.78 [cite web
url=http://www.physics.nau.edu/~tegler/research/survey.htm
title=Kuiper Belt Object Magnitudes and Surface Colors
accessdate=2006-11-05
last=Tegler |first=Stephen C.
date=2006-01-26 ]
magnitude = 20.4 (Perihelic)
abs_magnitude=1.56cite web
date=2007-11-08 last obs
title=JPL Small-Body Database Browser: 90377 Sedna (2003 VB12)
url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Sedna
accessdate=2008-06-11]
albedo=0.16&ndash;0.30
single_temperature=below 33 K

90377 Sedna (pronEng|ˈsɛdnə respell|SED|nə) is a trans-Neptunian object and a likely dwarf planet, discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. It is currently 88 AU from the Sun, about three times further than Neptune. For most of its orbit Sedna is farther from the Sun than any other known dwarf planet candidate. [ At present, though, Eris (dwarf planet) is further from the Sun than Sedna.]

Discovery

Considered a detached object,Jewitt, David, Morbidelli, Alessandro, & Rauer, Heike. (2007). "Trans-Neptunian Objects and Comets: Saas-Fee Advanced Course 35. Swiss Society for Astrophysics and Astronomy". Berlin: Springer. ISBN 3540719571. ] Lykawka, Patryk Sofia & Mukai, Tadashi. (2007). Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation. "Icarus" Volume 189, Issue 1, July , Pages 213-232. doi|10.1016/j.icarus.2007.01.001.] Sedna was discovered during a survey conducted with the Samuel Oschin telescope at Palomar Observatory near San Diego, California (USA) using Yale's 160 megapixel Palomar Quest camera and was observed within days on telescopes from Chile, Spain, and the USA (Arizona, and Hawaii). NASA's orbiting Spitzer Space Telescope was also pointed toward the object, but could not detect it &ndash; putting an upper-bound on its diameter at roughly three-quarters that of Pluto.

The object is named after Sedna, the Inuit goddess of the sea, who was believed to live in the cold depths of the Arctic Ocean. Before Sedna was officially named it had provisional designation mp|2003 VB|12.

Orbital characteristics

Sedna has a highly elliptical orbit, with its aphelion estimated at 975 AU and its perihelion at about 76.16 AU. At its discovery it was approaching perihelion and about 89.6 AU from the Sun. At the time of its discovery it was the most distant object in the solar system yet observed; although the orbits of some objects—like long-period comets—extend further than that of Sedna, they are basically too dim to be observed except near perihelion. Eris was later detected at 97 AU.

Sedna's precise orbital period is not yet known, but it is calculated at between 10.5 and 12.0 thousand years. It should reach perihelion in late 2075Lowell DES Perihelion Epoch = 2000.0 + (2479283.2278 − 2451545.0)/365.25 = 2075.9431 = (2076-1-1 - 20.7768 days) = 2075-12-11 ( [http://www.space.gs/jd.html Julian Date Converter] )] to mid 2076.cite web |url=http://home.comcast.net/~kpheider/Sedna2076.txt |title=Horizons Output for Sedna 2076/2114 |accessdate=2007-11-19 [http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=Sedna Horizons] ] Sedna will overtake Eris as the furthest known spheroid orbiting the Sun in 2114.

When first discovered, Sedna was believed to have an unusually long rotational period (20 to 50 days). A search was thus made for a natural satellite, the most likely cause for such a long rotation, but investigation by the Hubble Space Telescope in March 2004 observed no such object orbiting the planetoid. New measurements from the MMT telescope suggest a much shorter rotation period, only about 10 hours, rather typical for bodies of its size. [cite journal
url=http://arxiv.org/abs/astro-ph/0503673
title=On the Rotation Period of (90377) Sedna
first=B. Scott
last=Gaudi
coauthors=Krzysztof Z. Stanek, Joel D. Hartman, Matthew J. Holman, Brian A. McLeod (CfA)
journal=Astrophys.J.
volume= 629
year=2005
pages=L49–L52
doi=10.1086/444355]

A study done by Hal Levison and Alessandro Morbidelli of the Observatoire de la Côte d'Azur (OCA) in Nice, France, suggested that the most likely explanation for Sedna's orbit was that it had been perturbed by a close (~800 AU) pass by another star in the first 100 million years or so of the solar system's existence, possibly one of the other stars that formed out of the same collapsing nebula as the Sun.cite journal
journal=The Astronomical Journal
volume=128
pages=2564&ndash;2576
year=2004
title="Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12 (Sedna)"
first=Alessandro
last=Morbidelli
coauthors=Harold F. Levison
url=http://www.journals.uchicago.edu/doi/pdf/10.1086/424617
doi=10.1086/424617 [http://www.arxiv.org/abs/astro-ph/0403358 (Original Preprint)] ] They proposed another, less probable scenario that managed to explain Sedna's orbit very well &mdash;Sedna could have formed around a brown dwarf about 20 times less massive than the Sun and have been captured by the solar system when the brown dwarf passed through it.

Another possible explanation, advanced by Gomes, involves perturbations of Sedna's orbit by a hypothetical planetary-sized body in the inner Oort cloud. Recent simulations show that Sedna's orbital characteristics could be explained by perturbations by a Neptune-mass object at 2000 AU (or less), a Jupiter-mass at 5000 AU, or even an Earth-mass object at 1000 AU.cite journal
url=http://adsabs.harvard.edu/abs/2006Icar..184..589G
title=A distant planetary-mass solar companion may have produced distant detached objects
first=Rodney S.
last=Gomes
coauthors= John J. Matese, and Jack J. Lissauer
journal=Icarus
volume= 184
year=2006
pages=589–601
doi=10.1016/j.icarus.2006.05.026]

Another object, mpl|2000 CR|105, has an orbit similar to Sedna's but a bit less extreme: perihelion is 44.3 AU, aphelion is 394 AU, and the orbital period is 3240 years. Its orbit may have resulted from the same processes that produced Sedna's orbit.

Physical characteristics

---

thumb|410px|left|Sedna_compared_with_Eris,_Pluto,_Makemake,_Haumea,_Varuna,_Orcus,_Quaoar,_and_Earth.
#Earthrect 646 1714 2142 1994 The Earth
#Eris and Dysnomiacircle 226 412 16 Dysnomiacircle 350 626 197 (136199) Eris
#Pluto and Charoncircle 1252 684 86 Charoncircle 1038 632 188 (134340) Pluto
#Makemakecircle 1786 614 142 (136472) Makemake
#Haumeacircle 2438 616 155 (136108) Haumea
#Sednacircle 342 1305 137 (90377) Sedna
#Orcuscircle 1088 1305 114 (90482) Orcus
#Quaoarcircle 1784 1305 97 (50000) Quaoar
#Varunacircle 2420 1305 58 (20000) Varuna
#link to image (under all other links)rect 0 0 2749 1994

desc none
# - setting this to "bottom-right" will display a (rather large) icon linking to the graphic, if desired

#Notes:
#Details on the new coding for clickable images is here:
#While it may look strange, it's important to keep the codes for a particular system in order. The clickable coding treats the first object created in an area as the one on top.
#Moons should be placed on "top" so that their smaller circles won't disappear "under" their respective primaries.Sedna has an estimated diameter of between 1200 and 1600 kilometres. At the time of its discovery it was the largest object found in the solar system since Pluto was discovered in 1930. It is now generally believed to be the 5th largest known trans-Neptunian object after Eris, Pluto, dp|Makemake, and dp|Haumea.] Sedna is so far from the Sun that the temperature never rises above 33 kelvin (−240 °C; −400 °F).

Observations from Chile show that Sedna is one of the reddest objects in the solar system, nearly as red as Mars. Unlike Pluto and Charon, Sedna appears to have very little methane ice or water ice on its surface; Chad Trujillo and his colleagues at the Gemini Observatory in Hawaii suggest that Sedna's dark red color is caused by a hydrocarbon sludge, or tholin, like that found on 5145 Pholus. [cite web|url=http://www.newscientist.com/article.ns?id=dn7272
title=Distant planetoid Sedna gives up more secrets
year=2005
publisher=NewScientist.com news service
first=Maggie
last=McKee
accessdate=2005-03-05] Its surface is homogeneous in colour and spectrum; this is probably because Sedna, unlike objects nearer the sun, is rarely impacted by other bodies, which would expose bright patches like that on 8405 Asbolus. [cite web
last=Alexander
first=Amir
url=http://www.planetary.org/news/2005/0418_Sedna_Mysterious_Planetoid_Slowly.html
title=Sedna: Mysterious Planetoid Slowly Yielding Up Its Secrets
publisher=The Planetary Society
month=18 April
year=2005
accessdate=2006-09-15]

Sedna's and Triton's spectra have been recently compared suggesting the following common model of the surface: 24% Triton tholin, 7% amorphous carbon, 26% methanol ice with 33% methane.cite journal | author=M. A. Barucci, D. P. Cruikshank, E. Dotto, F. Merlin, F. Poulet, C. Dalle Ore, S. Fornasier and C. de Bergh| title=Is Sedna another Triton?| journal=Astronomy & Astrophysics | volume=439 | year=2005 | pages=L1–L4| doi=10.1051/0004-6361:200500144 ]

Classification

The discoverers have argued that Sedna is actually the first observed body belonging to the Oort cloud, saying that it is too far out to be considered a Scattered disk object. Because it is a great deal closer to the Sun than was expected for an Oort cloud object, and has an inclination roughly in line with the planets and the Kuiper belt, they described the planetoid as being an inner Oort cloud object, situated in the disc reaching from the Kuiper belt to the spherical part of the cloud.

A number of explanations for Sedna's unusual orbit have been put forward since, including a passing star [cite journal
journal=Nature
volume=432
pages=598&ndash;602
month=2 December
year=2004
title="Stellar encounters as the origin of distant Solar System objects in highly eccentric orbits"
first=Scott J.
last=Kenyon
coauthors=Benjamin C. Bromley
url=http://arxiv.org/abs/astro-ph?papernum=0412030
doi=10.1038/nature03136 ] and a distant, planet-sized object.Rodney S. Gomes, John J. Matese, and Jack J. Lissauer"A Distant Planetary-Mass Solar Companion May Have Produced Distant Detached Objects"To appear in Icarus (2006). [http://staff.on.br/rodneyg/companion/solar_companion.pdf Preprint] ]

Sedna, together with a few other objects (e.g. mpl|2000 CR|105), prompted suggestions of a new category of distant objects named "Extended scattered disc" (E-SDO), [http://www.obs-nice.fr/gladman/cr105.html "Evidence for an Extended Scattered Disk?"] ] "detached objects", D.Jewitt, A.Delsanti "The Solar System Beyond The Planets" in "Solar System Update : Topical and Timely Reviews in Solar System Sciences ", Springer-Praxis Ed., ISBN 3-540-26056-0 (2006) [http://www.ifa.hawaii.edu/faculty/jewitt/papers/2006/DJ06.pdf Preprint of the article (pdf)] ] "Distant Detached Objects" (DDO)Rodney S. Gomes, John J. Matese, and Jack J. Lissauer"A Distant Planetary-Mass Solar Companion May Have Produced Distant Detached Objects"To appear in Icarus (2006). [http://staff.on.br/rodneyg/companion/solar_companion.pdf Preprint] ] or "Scattered-Extended" in the formal classification by Deep Ecliptic Survey.J. L. Elliot, S. D. Kern, K. B. Clancy, A. A. S. Gulbis, R. L. Millis, M. W. Buie, L. H. Wasserman, E. I. Chiang, A. B. Jordan, D. E. Trilling, and K. J. Meech"The Deep Ecliptic Survey: A Search for Kuiper Belt Objects and Centaurs. II. Dynamical Classification, the Kuiper Belt Plane, and the Core Population."The Astronomical Journal, 129 (2006), pp. [http://alpaca.as.arizona.edu/~trilling/des2.pdf preprint] .]

The last classification, introduces a formal distinction between "Scattered-Near" objects (which could be scattered by Neptune) e.g. Eris from "Scattered-Extended" objects like Sedna. The distinction is made formally, using the orbital elements (see Tisserand's parameter).

The discovery of Sedna resurrected the question of which astronomical objects should be considered planets and which should not. On March 15, 2004, articles in the popular press reported that "the tenth planet has been discovered". This question was answered under the new International Astronomical Union definition of a planet, adopted on August 24, 2006. It is unknown whether or not Sedna is in hydrostatic equilibrium. If, as currently suspected,citeweb
url=http://web.gps.caltech.edu/~mbrown/dwarfplanets/
title=The Dwarf Planets
author=Michael E. Brown
publisher=California Institute of Technology, Department of Geological Sciences
accessdate=2008-02-16] it is, then it would qualify as a dwarf planet. Sedna has a Stern&ndash;Levison parameter estimated at between 8e|−5 and 6e|−3 times that of Pluto, [Stern&ndash;Levison parameter (using unlikely highest estimated mass) = ((7e|21) / (5.9736e|24))^2 / 12,059 yr = 1.14e|−10
(Sedna 1.14e|−10) / (Pluto 1.95e|−8) = 5.8e|−3] and therefore cannot be considered to have cleared the neighbourhood of its orbit, even though no other objects have yet been discovered in its vicinity.

ee also

*Scattered disk
*Asteroid
*Kuiper belt
*Oort cloud
*Planet
*Definition of planet
*Planet X &ndash; a hypothetical planet beyond Neptune which does not match the characteristics of Sedna
*Plutino
*protoplanetary disc &ndash; Sedna's orbit appears to imply a similar origin to the planets and asteroids.
*50000 Quaoar &ndash; a planetoid beyond Pluto's orbit, discovered in 2002.
*Trans-Neptunian object &ndash; an object beyond Neptune's orbit

References

Bibliography

* [http://www.gps.caltech.edu/~mbrown/papers/ps/sedna.pdf Discovery of a candidate inner Oort cloud planetoid] (Brown et.al., submitted to ApJ Letters, 16 March 2004)
*Hurt, Robert. [http://www.spitzer.caltech.edu/Media/releases/ssc2004-05/ssc2004-05b.shtml Artist's Concept of Sedna] . California, USA: "Infrared Processing and Analysis Center". 15 March 2004.
*Hurt, Robert. [http://www.spitzer.caltech.edu/Media/releases/ssc2004-05/ssc2004-05d.shtml Sedna's Orbit Comparisons] . California, USA: "Infrared Processing and Analysis Center". 15 March 2004.
*JPL. [http://www.spitzer.caltech.edu/Media/releases/ssc2004-05/release.shtml Most Distant Object in Solar System Discovered] . Press release: "Jet Propulsion Laboratory". 15 March 2004.
*Whitehourse, David. [http://news.bbc.co.uk/1/hi/sci/tech/3625233.stm Sedna has no moon, say astronomers] . BBC News. 14 April 2004.

External links

* [http://www.nasa.gov/vision/universe/solarsystem/planet_like_body.html NASA's Sedna page] (Discovery Photos)
* [http://www.gps.caltech.edu/~mbrown/sedna/ Mike Brown's Sedna page]
* [http://www.spitzer.caltech.edu/Media/releases/ssc2004-05/release.shtml Official press release by NASA JPL/SCC]
* [http://antwrp.gsfc.nasa.gov/apod/ap040604.html Astronomy Picture of the Day 04 July 2004 &ndash; Artist's rendering of view from Sedna]
* [http://www.boulder.swri.edu/~hal/CR105.html Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects mp|2000 CR|105 and mp|2003 VB|12 (Sedna)] by Alessandro Morbidelli and Harold F. Levison
* [http://cfa-www.harvard.edu/mpec/K04/K04S73.html MPEC 2004-S73: Comment on the naming of Sedna]
* [http://www.washingtonpost.com/wp-dyn/articles/A21549-2005Feb13.html Distant Object Could Hold Secrets to Earth's Past]
* [http://seds.lpl.arizona.edu/nineplanets/nineplanets/sedna.html Sedna] on [http://seds.lpl.arizona.edu/nineplanets/nineplanets/nineplanets.html The Nine Planets Solar System Tour]
* [http://hubblesite.org/newscenter/archive/releases/2004/14/text/ Hubblesite image April 14, 2004]
* [http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Sedna;orb=1;view=Far Orbital simulation] from JPL (Java) / [http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=Sedna Ephemeris]