90482 Orcus

Short description: Trans-Neptunian object and dwarf planet

90482 Orcus

Orcus and its moon Vanth imaged by the Hubble Space Telescope in 2006

Discovery[1][2]
Discovered by| M. E. Brown
C. Trujillo
D. Rabinowitz
Discovery date| 17 February 2004
Designations

MPC designation

| (90482) Orcus
Pronunciation| /ˈɔːrkəs/[7]
Named after| Orcus (Roman mythology)[3]

Alternative designations

| 2004 DW
Minor planet category| TNO[1] * plutino[4][5]
dwarf planet[6]
Adjectives| Orcean /ˈɔːrsiən/[8]
Orbital characteristics[1]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 2
Observation arc| 68.16 yr (24,894 days)
Earliest precovery date| 8 November 1951
|{{{apsis}}}|helion}}| 48.067 AU (7.1907 Tm)
|{{{apsis}}}|helion}}| 30.281 AU (4.5300 Tm)

Semi-major axis

| 39.174 AU (5.8603 Tm)
Eccentricity| 0.22701
Orbital period| 245.19 yr (89,557 days)
Mean anomaly| 181.735°
Mean motion| 0° 0m 14.472s / day
Inclination| 20.592°
Longitude of ascending node| 268.799°
|{{{apsis}}}|helion}}| ≈ 9 January 2143[9]
±4 days

|{{{apsis}}}|helion}}

| 72.310°
Known satellites| Vanth
Physical characteristics
Dimensions| 910+50
−40 km[10] 917±25 km[11]
Mass| (6.348±0.019)×1020 kg (system)[6]
Mean density| 1.53+0.15
−0.13 g/cm3[11]

Equatorial surface gravity

| ≈ 0.2 m/s2

Equatorial escape velocity

| ≈ 0.43 km/s
Geometric albedo| 0.231+0.018
−0.011[11]
Physics| < 44 K[12]

Spectral type

| (neutral)[12]
B–V =0.68[13]
V–R = 0.37[13]
Apparent magnitude| 19.1 (opposition)[14]
Absolute magnitude (H)| 2.31±0.03 (integral),[11] 2.41±0.05[15]

Orcus (90482 Orcus, provisional designation 2004 DW) is a trans-Neptunian dwarf planet with a large moon, Vanth.[6] It has a diameter of 910 km (570 mi). The surface of Orcus is relatively bright with albedo reaching 23 percent, neutral in color and rich in water ice. The ice is predominantly in crystalline form, which may be related to past cryovolcanic activity. Other compounds like methane or ammonia may also be present on its surface. Orcus was discovered by American astronomers Michael Brown, Chad Trujillo, and David Rabinowitz on 17 February 2004.

Orcus is a plutino, a trans-Neptunian object that is locked in a 2:3 resonance with the ice giant Neptune, making two revolutions around the Sun to every three of Neptune's.[4] This is much like Pluto, except that the phase of Orcus's orbit is opposite to Pluto's: Orcus is at aphelion (most recently in 2019) around when Pluto is at perihelion (most recently in 1989) and vice versa.[16] Orcus is the largest known plutino after Pluto itself. The perihelion of Orcus's orbit is around 120° from that of Pluto, while the eccentricities and inclinations are similar. Because of these similarities and contrasts, along with its large moon Vanth that recalls Pluto's large moon Charon, Orcus has been regarded as the anti-Pluto.[17] This was a major consideration in selecting its name, as the deity Orcus was the Roman/Etruscan equivalent of the Roman/Greek Pluto.[17]

## Contents

* 1 History
* 1.1 Discovery
* 1.2 Name and symbol
* 2 Orbit and rotation
* 3 Physical characteristics
* 3.1 Size and magnitude
* 3.2 Mass and density
* 3.3 Spectra and surface
* 3.4 Cryovolcanism
* 4 Satellite
* 5 See also
* 6 References
* 7 External links

## History

### Discovery

Discovery image of Orcus taken in 2004[18]

Orcus was discovered on 17 February 2004, by American astronomers Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University. Precovery images taken by the Palomar Observatory as early as 8 November 1951 were later obtained from the Digitized Sky Survey.[2]

### Name and symbol

The minor planet Orcus was named after one of the Roman gods of the underworld, Orcus. While Pluto (of Greek origin) was the ruler of the underworld, Orcus (of Etruscan origin) was a punisher of the condemned. The name was published by the Minor Planet Center on 26 November 2004 (M.P.C. 53177).[19] Under the guidelines of the International Astronomical Union's (IAU) naming conventions, objects with a similar size and orbit to that of Pluto are named after underworld deities. Accordingly, the discoverers suggested naming the object after Orcus, the Etruscan god of the underworld and punisher of broken oaths. The name was also a private reference to the homonymous Orcas Island, where Brown's wife had lived as a child and that they visit frequently.[20]

On 30 March 2005, Orcus's moon, Vanth, was named after a winged female demon, Vanth, of the Etruscan underworld. She could be present at the moment of death, and frequently acted as a psychopomp, a guide of the deceased to the underworld.[21]

Planetary symbols are no longer much used in astronomy, so Orcus never received a symbol in the astronomical literature. An Orcus symbol (), mostly used among astrologers,[22] is included in Unicode as U+1F77F.[23] The symbol was designed by Denis Moskowitz, a software engineer in Massachusetts; it is an OR monogram, designed to resemble both a skull and an orca's gape.[24]

## Orbit and rotation

Orcus is in a 2:3 orbital resonance with Neptune, having an orbital period of 245 years,[4][1] and is classified as a plutino.[2] Its orbit is moderately inclined at 20.6 degrees to the ecliptic.[1] Orcus's orbit is similar to Pluto's (both have perihelia above the ecliptic), but is oriented differently. Although at one point its orbit approaches that of Neptune, the resonance between the two bodies means that Orcus itself is always a great distance away from Neptune (there is always an angular separation of over 60 degrees between them). Over a 14,000-year period, Orcus stays more than 18 AU from Neptune.[16] Because their mutual resonance with Neptune constrains Orcus and Pluto to remain in opposite phases of their otherwise very similar motions, Orcus is sometimes described as the "anti-Pluto".[17] Orcus last reached its aphelion (farthest distance from the Sun) in 2019 and will come to perihelion (closest distance to the Sun) around 9 January 2143.[9] Simulations by the Deep Ecliptic Survey show that over the next 10 million years Orcus may acquire a perihelion distance (qmin) as small as 27.8 AU.[4]

The rotation period of Orcus is uncertain, as different photometric surveys have produced different results. Some show low amplitude variations with periods ranging from 7 to 21 hours, whereas others show no variability.[25] The rotational axis of Orcus probably coincides with the orbital axis of its moon, Vanth. This means that Orcus is currently viewed pole-on, which could explain the near absence of any rotational modulation of its brightness.[25][26] Astronomer José Luis Ortiz and colleagues have derived a possible rotation period of about 10.5 hours, assuming that Orcus is not tidally locked with Vanth.[26] If, however, the primary is tidally locked with the satellite, the rotational period would coincide with the 9.7-day orbital period of Vanth.[26]

Mean-motion resonance of Orcus (rotating frame with a period equal to Neptune's orbital period)

The orbits of Orcus (blue), Pluto (red) and Neptune (grey). Orcus and Pluto are shown in the April 2006 positions. The dates of their perihelia (q) and aphelia (Q) are also marked.

## Physical characteristics

### Size and magnitude

Orcus compared to Earth and the Moon

Long-exposure photograph of Orcus at visual magnitude 19.2

The absolute magnitude of Orcus is approximately 2.3.[11] The detection of Orcus by the Spitzer Space Telescope in the far infrared[27] and by Herschel Space Telescope in submillimeter estimates its diameter at 958.4 km (595.5 mi), with an uncertainty of 22.9 km (14.2 mi).[11] Orcus appears to have an albedo of about 21–25 percent,[11] which may be typical of trans-Neptunian objects approaching the 1,000 km (620 mi) diameter range.[28] The magnitude and size estimates were made under the assumption that Orcus is a singular object. The presence of a relatively large satellite, Vanth, may change them considerably. The absolute magnitude of Vanth is estimated at 4.88, which means that it is about 11 times fainter than Orcus itself.[15] The ALMA submillimeter measurements taken in 2016 showed that Vanth has a relatively large size of 475 km (295 mi) with albedo of about 8 percent while Orcus's has a slightly smaller size of 910 km (570 mi).[10] Using a stellar occultation by Vanth in 2017, Vanth's diameter has been determined to be 442.5 km (275.0 mi), with an uncertainty of 10.2 km (6.3 mi).[29] Michael Brown's website lists Orcus as a dwarf planet with "near certainty",[30] Tancredi concludes that it is one,[31] and is massive enough to be considered one under the 2006 draft proposal of the IAU,[32] but the IAU has not formally recognized it as such.[33][34]

### Mass and density

Orcus and Vanth are known to constitute a binary system. The mass of the system has been estimated to be (6.348±0.019)×1020 kg,[6] approximately equal to that of the Saturnian moon Tethys (6.175×1020 kg).[35] Compared to the most massive known dwarf planet, Eris, the mass of the Orcus system is about 3.8 percent that of Eris (1.66×1022 kg).[15][36] How this mass is partitioned between Orcus and Vanth depends on their relative densities. If Vanth were 0.8 g/cm3 (typical for a TNO in this size range), it would be about 5% of Orcus's mass; if it had the same density of Orcus (that is, the system density of 1.53 g/cm3), then it would be about 20% of Orcus's mass. The low albedo of Vanth compared to Orcus suggests that their compositions are different and that Vanth's density is relatively low. Thus the mass of Orcus is likely to be close to the system mass.[10][29]

### Spectra and surface

Artistic comparison of Pluto, Eris, Haumea]], Makemake, Gonggong, Quaoar, Sedna, Orcus, Salacia, 2002 MS4, and Earth along with the Moon. [v * d * e]

The first spectroscopic observations in 2004 showed that the visible spectrum of Orcus is flat (neutral in color) and featureless, whereas in the near-infrared there were moderately strong water absorption bands at 1.5 and 2.0 μm.[37] The neutral visible spectrum and strong water absorption bands of Orcus showed that Orcus appeared different from other trans-Neptunian objects, which typically have a red visible spectrum and often featureless infrared spectra.[37] Further infrared observations in 2004 by the European Southern Observatory and the Gemini telescope gave results consistent with mixtures of water ice and carbonaceous compounds, such as tholins.[13] The water and methane ices can cover no more than 50 percent and 30 percent of the surface, respectively.[38] This means the proportion of ice on the surface is less than on Charon, but similar to that on Triton.[38]

Later in 2008–2010 new infrared spectroscopic observations with a higher signal-to-noise ratio revealed additional spectral features. Among them are a deep water ice absorption band at 1.65 μm, which is an evidence of the crystalline water ice on the surface of Orcus, and a new absorption band at 2.22 μm. The origin of the latter feature is not completely clear. It can be caused either by ammonia/ammonium dissolved in the water ice or by methane/ethane ices.[12] The radiative transfer modeling showed that a mixture of water ice, tholins (as a darkening agent), ethane ice and ammonium ion (NH4+) provides the best match to the spectra, whereas a combination of water ice, tholins, methane ice and ammonia hydrate gives a slightly inferior result. On the other hand, a mixture of only ammonia hydrate, tholins and water ice failed to provide a satisfactory match.[25] So, as of 2010, the only reliably identified compounds on the surface of Orcus are crystalline water ice and, possibly, dark tholins. A firm identification of ammonia, methane and other hydrocarbons requires better infrared spectra.[25]

Orcus sits at the threshold for trans-Neptunian objects massive enough to retain volatiles such as methane on the surface.[25] The reflectance spectrum of Orcus shows the deepest water-ice absorption bands of any Kuiper belt object that is not associated with the Haumea collisional family.[15] The large icy satellites of Uranus have infrared spectra quite similar to that of Orcus.[15] Among other trans-Neptunian objects, the large plutino 2003 AZ84 and Pluto's moon Charon both have similar surface spectra to Orcus,[12] with flat, featureless visible spectra and moderately strong water ice absorption bands in the near-infrared.[25]

### Cryovolcanism

Crystalline water ice on the surfaces of trans-Neptunian objects should be completely amorphized by the galactic and Solar radiation in about 10 million years.[12] Thus the presence of crystalline water ice, and possibly ammonia ice, may indicate that a renewal mechanism was active in the past on the surface of Orcus.[12] Ammonia so far has not been detected on any trans-Neptunian object or icy satellite of the outer planets other than Miranda.[12] The 1.65 μm band on Orcus is broad and deep (12%), as on Charon, Quaoar, Haumea, and icy satellites of giant planets.[12] Some calculations indicate that cryovolcanism, which is considered one of the possible renewal mechanisms, may indeed be possible for trans-Neptunian objects larger than about 1,000 km (620 mi).[25] Orcus may have experienced at least one such episode in the past, which turned the amorphous water ice on its surface into crystalline. The preferred type of volcanism may have been explosive aqueous volcanism driven by an explosive dissolution of methane from water–ammonia melts.[25]

## Satellite

Orcus and Vanth imaged by Hubble in 2006

Main page: Astronomy:Vanth (moon)

Orcus has one known moon, Vanth (full designation (90482) Orcus I Vanth). It was discovered by Michael Brown and T.-A. Suer using discovery images taken by the Hubble Space Telescope on 13 November 2005.[39] The discovery was announced in an IAU Circular notice published on 22 February 2007.[40] A spatially resolved submillimeter imaging of Orcus–Vanth system in 2016 showed that Vanth has a relatively large size of 475 km (295 mi), with an uncertainty of 75 km (47 mi).[10] That estimate for Vanth is in good agreement with the size of about 442.5 km (275.0 mi) derived from a stellar occultation in 2017.[29] Like Charon compared to Pluto, Vanth is quite large compared to Orcus, and is one reason for characterizing Orcus as the 'anti-Pluto'. If Orcus is a dwarf planet, Vanth would be the third-largest known dwarf-planet moon, after Charon and Dysnomia. The ratio of masses of Orcus and Vanth is uncertain, possibly anywhere from 1:33 to 1:12.[41]

## See also

* List of possible dwarf planets
* List of trans-Neptunian objects
* List of Solar System objects by size

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 "JPL Small-Body Database Browser: 90482 Orcus (2004 DW)". Jet Propulsion Laboratory. 29 January 2020. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2090482.
2. ↑ 2.0 2.1 2.2 "90482 Orcus (2004 DW)". Minor Planet Center. http://www.minorplanetcenter.net/db_search/show_object?object_id=90482.
3. ↑ Schmadel, Lutz D. (2006). "(90482) Orcus [39.5, 0.22, 20.5]". Dictionary of Minor Planet Names – (90482) Orcus, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 236. doi:10.1007/978-3-540-34361-5_2818. ISBN 978-3-540-34361-5.
4. ↑ 4.0 4.1 4.2 4.3 Buie, Marc W. (22 December 2007). "Orbit Fit and Astrometric record for 90482". SwRI (Space Science Department). http://www.boulder.swri.edu/~buie/kbo/astrom/90482.html.
5. ↑ "MPEC 2009-E53 :Distant Minor Planets (2009 MAR. 30.0 TT)". Minor Planet Center. 11 March 2009. http://www.minorplanetcenter.net/mpec/K09/K09E53.html.
6. ↑ 6.0 6.1 6.2 6.3 Grundy, Will M.; Noll, Keith S.; Roe, Henry G.; Buie, Marc W.; Porter, Simon B.; Parker, Alex H.; Nesvorný, David; Levison, Harold F. et al. (2019). "Mutual Orbit Orientations of Transneptunian Binaries". Icarus 334: 62–78. doi:10.1016/j.icarus.2019.03.035. ISSN 0019-1035. Bibcode: 2019Icar..334...62G. http://www2.lowell.edu/users/grundy/abstracts/preprints/2019.TNB_orbits.pdf. Retrieved 2019-11-13.
7. ↑ "Orcus". Dictionary.com Unabridged. Random House. https://www.dictionary.com/browse/Orcus.
8. ↑ Angley (1847) De Clifford, the philosopher
9. ↑ 9.0 9.1 JPL Horizons Observer Location: @sun (perihelion occurs when deldot changes from negative to positive)
10. ↑ 10.0 10.1 10.2 10.3 Brown, Michael E.; Butler, Bryan J. (22 January 2018). "Medium-sized satellites of large Kuiper belt objects". The Astronomical Journal 156 (4): 164. doi:10.3847/1538-3881/aad9f2.
11. ↑ 11.0 11.1 11.2 11.3 11.4 11.5 11.6 Fornasier, S. 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. doi:10.1051/0004-6361/201321329. Bibcode: 2013A&A...555A..15F.
12. ↑ 12.0 12.1 12.2 12.3 12.4 12.5 12.6 12.7 Barucci, M. A. et al. (2008). "Surface composition and temperature of the TNO Orcus". Astronomy and Astrophysics 479 (1): L13–L16. doi:10.1051/0004-6361:20079079. Bibcode: 2008A&A...479L..13B.
13. ↑ 13.0 13.1 13.2 de Bergh, C.; A. Delsanti; G. P. Tozzi; E. Dotto; A. Doressoundiram; M. A. Barucci (2005). "The Surface of the Transneptunian Object 9048 Orcus". Astronomy & Astrophysics 437 (3): 1115–1120. doi:10.1051/0004-6361:20042533. Bibcode: 2005A&A...437.1115D.
14. ↑ "HORIZONS Web-Interface". JPL Solar System Dynamics. http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=Orcus.
15. ↑ 15.0 15.1 15.2 15.3 15.4 Brown, M.E.; Ragozzine, D.; Stansberry, J.; Fraser, W.C. (2010). "The size, density, and formation of the Orcus-Vanth system in the Kuiper belt". The Astronomical Journal 139 (6): 2700–2705. doi:10.1088/0004-6256/139/6/2700. Bibcode: 2010AJ....139.2700B.
16. ↑ 16.0 16.1 "MPEC 2004-D15 : 2004 DW". Minor Planet Center. 20 February 2004. http://www.minorplanetcenter.net/mpec/K04/K04D15.html.
17. ↑ 17.0 17.1 17.2 Michael E. Brown (23 March 2009). "S/2005 (90482) 1 needs your help". Mike Brown's Planets (blog). http://www.mikebrownsplanets.com/2009/03/s1-90482-2005-needs-your-help.html.
18. ↑ "Distant Planetoid". NASA. https://solarsystem.nasa.gov/resources/401/distant-planetoid/.
19. ↑ "MPC/MPO/MPS Archive". Minor Planet Center. http://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html.
20. ↑ Michael E. Brown (6 April 2009). "Orcus Porcus". Mike Brown's Planets (blog). http://www.mikebrownsplanets.com/2009/04/orcus-porcus.html.
21. ↑ Wm. Robert Johnston (4 March 2007). "(90482) Orcus". Johnston's Archive. http://www.johnstonsarchive.net/astro/astmoons/am-90482.html.
22. ↑ Miller, Kirk (26 October 2021). "Unicode request for dwarf-planet symbols". https://www.unicode.org/L2/L2021/21224-dwarf-planet-syms.pdf.
23. ↑ Proposed New Characters: The Pipeline
24. ↑ Anderson, Deborah (4 May 2022). "Out of this World: New Astronomy Symbols Approved for the Unicode Standard". The Unicode Consortium. http://blog.unicode.org/2022/05/out-of-this-world-new-astronomy-symbols.html.
25. ↑ 25.0 25.1 25.2 25.3 25.4 25.5 25.6 25.7 A. DelsantiExpression error: Unrecognized word "etal". (2010). "Methane, ammonia, and their irradiation products at the surface of an intermediate-size KBO? A portrait of Plutino (90482) Orcus". Astronomy and Astrophysics 627 (2): 1057. doi:10.1051/0004-6361/201014296. Bibcode: 2010A&A...520A..40D.
26. ↑ 26.0 26.1 26.2 Ortiz, J. L.; Cikota, A.; Cikota, S.; Hestroffer, D.; Thirouin, A.; Morales, N.; Duffard, R.; Gil-Hutton, R. et al. (2010). "A mid-term astrometric and photometric study of trans-Neptunian object (90482) Orcus". Astronomy & Astrophysics 525: A31. doi:10.1051/0004-6361/201015309. Bibcode: 2011A&A...525A..31O.
27. ↑ Stansberry, J.; Grundy, W.; Brown, M.; Cruikshank, D.; Spencer, J.; Trilling, D.; Margot, J.-L. (2008). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from the Spitzer Space Telescope". in M. A. Barucci. The Solar System Beyond Neptune. Tucson: University of Arizona Press. pp. 161–179. ISBN 978-0816527557. Bibcode: 2008ssbn.book..161S.
28. ↑ Wm. Robert Johnston (17 September 2008). "TNO/Centaur diameters and albedos". Johnston's Archive. http://www.johnstonsarchive.net/astro/tnodiam.html.
29. ↑ 29.0 29.1 29.2 Sickafoose, A.A.; Bosh, A.S.; Levine, S.E.; Zuluaga, C.A.; Genade, A.; Schindler, K.; Lister, T.A.; Person, M.J. (21 October 2018). "A stellar occultation by Vanth, a satellite of (90482) Orcus". Icarus 319: 657–668. doi:10.1016/j.icarus.2018.10.016. Bibcode: 2019Icar..319..657S.
30. ↑ Michael E. Brown (23 Sep 2011). "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. http://www.gps.caltech.edu/~mbrown/dps.html.
31. ↑ Tancredi, G.; Favre, S. (2008). "Which are the dwarfs in the solar system?". Asteroids, Comets, Meteors. http://www.lpi.usra.edu/meetings/acm2008/pdf/8261.pdf.
32. ↑ "The Path to Defining Planets". Harvard-Smithsonian Center for Astrophysics and IAU EC Planet Definition Committee chair. 16 August 2006. p. 4. https://www.iau.org/static/publications/ga_newspapers/20060812.pdf.
33. ↑ "Planetary Names: Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. International Astronomical Union (Working Group for Planetary System Nomenclature). http://planetarynames.wr.usgs.gov/Page/Planets#DwarfPlanets.
34. ↑ NASA. "List of Dwarf Planets". http://solarsystem.nasa.gov/planets/profile.cfm?Object=Dwarf&Display=Sats.
35. ↑ Jacobson, R. A.; Antreasian, P. G.; Bordi, J. J.; Criddle, K. E.; Ionasescu, R.; Jones, J. B.; Mackenzie, R. A.; Meek, M. C. et al. (December 2006). "The Gravity Field of the Saturnian System from Satellite Observations and Spacecraft Tracking Data". The Astronomical Journal 132 (6): 2520–2526. doi:10.1086/508812. Bibcode: 2006AJ....132.2520J.
36. ↑ Brown, Michael E.; Schaller, Emily L. (15 June 2007). "The Mass of Dwarf Planet Eris". Science 316 (5831): 1585. doi:10.1126/science.1139415. PMID 17569855. Bibcode: 2007Sci...316.1585B. http://hubblesite.org/pubinfo/pdf/2007/24/pdf.pdf.
37. ↑ 37.0 37.1 Fornasier, S.; Dotto, E.; Barucci, M.A.; Barbieri, C. (2004). "Water ice on the surface of the large TNO 2004 DW". Astronomy & Astrophysics 422 (2): L43–L46. doi:10.1051/0004-6361:20048004. Bibcode: 2004A&A...422L..43F.
38. ↑ 38.0 38.1 Trujillo, Chadwick A.; Brown, Michael E.; Rabinowitz, David L.; Geballe, Thomas R. (2005). "Near-Infrared Surface Properties of the Two Intrinsically Brightest Minor Planets: (90377) Sedna and (90482) Orcus". The Astrophysical Journal 627 (2): 1057–1065. doi:10.1086/430337. Bibcode: 2005ApJ...627.1057T.
39. ↑ Daniel W. E. Green (22 February 2007). "IAUC 8812: Sats OF 2003 AZ_84, (50000), (55637),, (90482)". International Astronomical Union Circular. http://www.cbat.eps.harvard.edu/iauc/08800/08812.html.
40. ↑ Wm. Robert Johnston (4 March 2007). "(90482) Orcus". Johnston's Archive. http://www.johnstonsarchive.net/astro/astmoons/am-90482.html.
41. ↑ Carry, B.; Hestroffer, D.; Demeo, F. E.; Thirouin, A.; Berthier, J.; Lacerda, P.; Sicardy, B.; Doressoundiram, A. et al. (2011). "Integral-field spectroscopy of (90482) Orcus-Vanth". Astronomy & Astrophysics 534: A115. doi:10.1051/0004-6361/201117486. Bibcode: 2011A&A...534A.115C.

## External links

* MPEC 2004-D09 announcing the discovery but attributing it to Raymond J. Bambery, Steven H. Pravdo, Michael D. Hicks, Kenneth J. Lawrence, Daniel MacDonald, Eleanor Helin and Robert Thicksten / NEAT
* MPEC 2004-D13 correcting MPEC 2004-D09
* Chad Trujillo's page on 2004 DW
* Orcus of the Outer Solar System, Astronomy Picture of the Day, 25 March 2009
* New world found far beyond Pluto, David Whitehouse, BBC News, 3 March 2004
* A New Kuiper Belt Giant, Stuart Goldman, Sky & Telescope, 24 February 2004
* 90482 Orcus at the JPL Small-Body Database
* Close approach * Discovery * Ephemeris * Orbit diagram * Orbital elements * Physical parameters

* v
* t
* e

Dwarf planets

* List of possible dwarf planets
* Former dwarf planets
* Phoebe
* Triton
* Vesta
* Mesoplanet
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Asteroid belt|

| IAU|

* Ceres

|

Possible|

* Hygiea
* Interamnia

Centaurs|

| Possible|

* Ceto
* Chariklo
* Chiron
* 1995 SN55
* 2010 TY53

|

Plutinos|

| IAU|

* Pluto

|

Possible|

* Huya
* Ixion
* Orcus
* 2001 QF298
* 2002 VR128
* 2002 XV93
* 2003 AZ84
* 2003 UZ413
* 2003 VS2
* 2007 JH43

Twotinos|

| Possible|

* 2002 WC19

|

Cubewanos|

| IAU|

* Makemake

|

Possible|

* Altjira
* Chaos
* Praamzius
* Quaoar
* Rhadamanthus
* Salacia
* Sila–Nunam
* Varda
* Varuna
* 1998 SN165
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* 2004 GV9
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* 2005 RN43
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* 2005 UQ513
* 2007 JJ43
* 2010 FX86
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Scattered disc|

| IAU|

* Eris

|

Possible|

* Dziewanna
* Gǃkúnǁʼhòmdímà
* 1996 GQ21
* 1996 TL66
* 1999 CC158
* 2001 UR163
* 2002 TC302
* 2004 XA192
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* 2005 RM43
* 2006 QH181
* 2007 OR10
* 2008 OG19
* 2010 KZ39
* 2010 RE64
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* 2010 TJ
* 2010 VZ98
* 2012 HH2
* 2013 FY27
* 2018 VG18

Detached objects|

| Possible|

* 1995 TL8
* 2000 CR105
* 2003 FY128
* 2003 QX113
* 2004 VN112
* 2004 XR190
* 2005 TB190
* 2008 ST291
* 2010 GB174

|

Sednoids|

| Possible|

* Sedna
* 2015 TG387
* 2012 VP113

|

Other / unknown
resonances|

| IAU|

* Haumea

|

Possible|

* FarFarOut
* V774104
* 1999 CD158
* 1999 DE9
* 1999 KR16
* 2000 YW134
* 2001 YH140
* 2002 XW93
* 2010 VK201
* 2011 FW62
* 2011 GM27
* 2013 FZ27
* 2014 UM33

* Category

* v
* t
* e

Trans-Neptunian objects

TNO classes|

* Cubewanos
* Scattered-disc objects
* Detached objects
* Resonant objects
* Neptune trojans
* Plutinos
* Twotinos
* TNO moons

Dwarf planets (moons)|

* Pluto
* Charon
* Styx
* Nix
* Kerberos
* Hydra
* Haumea
* Namaka
* Hiʻiaka
* Makemake
* S/2015 (136472) 1
* Eris
* Dysnomia

Sednoids|

* 90377 Sedna
* 2012 VP113
* 2015 TG387

* v
* t
* e

Solar System

* Sun
* Mercury
* Venus
* Earth
* Mars
* Ceres
* Jupiter
* Saturn
* Uranus
* Neptune
* Pluto
* Haumea
* Makemake
* Eris

| Planets|

* Terrestrial planets
* Mercury
* Venus
* Earth
* Mars

* Giant planets
* Jupiter
* Saturn
* Uranus
* Neptune

* Dwarf planets
* Ceres
* Pluto
* Haumea
* Makemake
* Eris

|

Rings|

* Jovian
* Saturnian (Rhean)
* Charikloan
* Chironean
* Uranian
* Neptunian
* Haumean

Moons|

* Terrestrial
* Moon
* other near-Earth objects
* Martian
* Phobos
* Deimos
* Jovian
* Ganymede
* Callisto
* Io
* Europa
* all 79
* Saturnian
* Titan
* Rhea
* Iapetus
* Dione
* Tethys
* Enceladus
* Mimas
* Hyperion
* Phoebe
* all 82
* Uranian
* Titania
* Oberon
* Umbriel
* Ariel
* Miranda
* all 27
* Neptunian
* Triton
* Proteus
* Nereid
* all 14
* Plutonian
* Charon
* Nix
* Hydra
* Kerberos
* Styx
* Eridian
* Dysnomia
* Haumean
* Hiʻiaka
* Namaka
* Makemakean
* S/2015 (136472) 1

Exploration
(outline)|

* Colonization
* Discovery
* astronomy
* historical models
* timeline
* Human spaceflight
* space stations
* list
* Space probes
* timeline
* list

* Mercury
* Venus
* Moon
* mining
* Mars
* Ceres
* Asteroids
* mining
* Comets
* Jupiter
* Saturn
* Uranus
* Neptune
* Pluto
* Deep space

Hypothetical
objects|

* Fifth giant
* Nemesis
* Phaeton
* Planet Nine
* Planet V
* Planet X
* Theia
* Tyche
* Vulcan
* Vulcanoids
* Subsatellites

Lists|

* Comets
* Dwarf planets (possible)
* Gravitationally rounded objects
* Minor planets
* names
* Natural satellites
* Solar System models
* Solar System objects
* by size
* by discovery date

| Small Solar
System bodies|

* Comets
* Damocloids
* Meteoroids
* Minor planets
* moons
* Planetesimal

* Mercury-crossers
* Venus-crossers
* Venus trojans
* Near-Earth objects
* Earth-crossers
* Earth trojans
* Mars-crossers
* Mars trojans

* Asteroid belt
* Asteroids
* Ceres
* Pallas
* Juno
* Vesta
* first 1000
* families
* exceptional
* Kirkwood gap
* Main-belt comets

* Jupiter-crossers
* Jupiter trojans
* Centaurs
* Saturn-crossers
* Uranus-crossers
* Uranus trojans
* Neptune-crossers
* Neptune trojans
* Cis-Neptunian objects
* Trans-Neptunian objects

* Plutoids
* Kuiper belt
* Cubewanos
* Plutinos
* Detached objects
* Hills cloud
* Oort cloud
* Scattered disc
* Sednoids

|

Formation
and evolution|

* Accretion
* Accretion disk
* Asteroid belt
* Circumplanetary disk
* Circumstellar disc
* Circumstellar envelope
* Cosmic dust
* Debris disk
* Detached object
* Disrupted planet
* Excretion disk
* Exoplanetary Circumstellar Environments and Disk Explorer
* Exozodiacal dust
* Extraterrestrial materials
* Extraterrestrial sample curation
* Giant-impact hypothesis
* Gravitational collapse
* Hills cloud
* Interplanetary dust cloud
* Interplanetary medium
* Interplanetary space
* Interstellar cloud
* Interstellar dust
* Interstellar medium
* Interstellar space
* Kuiper belt
* List of interstellar and circumstellar molecules
* Merging stars
* Molecular cloud
* Nebular hypothesis
* Oort cloud
* Outer space
* Planetary migration
* Planetary system
* Planetesimal
* Planet formation
* Protoplanetary disk
* Ring system
* Rubble pile
* Sample-return mission
* Scattered disc
* Star formation

* Outline of the Solar System
*   *   *

Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe
Each arrow (→) may be read as "within" or "part of".

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Original source: https://en.wikipedia.org/wiki/90482 Orcus. Read more

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