90482 Orcus

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90482 Orcus
Discovery A
Discoverer M. Brown,
C. Trujillo,
D. Rabinowitz
Discovery date February 17, 2004
Alternate
designations
B
2004 DW
Category Plutino
Orbital elements C
Epoch November 10, 1951 (JD 2433960.5)
Eccentricity (e) 0.22552
Semi-major axis (a) 5896.946 Gm (39.419 AU)
Perihelion (q) 4567.091 Gm (30.53 AU)
Aphelion (Q) 7226.801 Gm (48.31 AU)
Orbital period (P) 90396.4 d (247.492 a)
Mean orbital speed 4.68 km/s
Inclination (i) 20.55233°
Longitude of the
ascending node
(Ω)
268.586°
Argument of
perihelion
(ω)
73.8325°
Mean anomaly (M) 79.561°
Physical characteristics D
Dimensions 840 - 1880 km
Mass 6.2 - 7.0×1020 kg
Density 2.0? g/cm³
Surface gravity 0.2348 - 0.5254 m/s²
Escape velocity 0.4441 - 0.9939 km/s
Rotation period  ? d
Spectral class B-V=0.68; V-R=0.37 [1]
Absolute magnitude 2.3
Albedo (geometric) 0.09 (assumed)
Mean surface
temperature
~45 K
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90482 Orcus (originally known by the provisional designation 2004 DW) is a Kuiper Belt object (KBO) that was discovered by Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University. The discovery images of this object were acquired on February 17, 2004. Precovery images as early as November 8, 1951 were later identified.

Contents

[edit] Orbit

This diagram shows the orbits of Orcus (blue), Pluto (red) and Neptune (grey). The three objects are shown in the current positions (as of April 2006). The dates of their perihelia (q) and aphelia (Q) are also marked.
Enlarge
This diagram shows the orbits of Orcus (blue), Pluto (red) and Neptune (grey). The three objects are shown in the current positions (as of April 2006). The dates of their perihelia (q) and aphelia (Q) are also marked.

Orcus is a typical plutino (an object in 2:3 orbital resonance with Neptune). Orcus's orbit is shaped similarly to Pluto's (both have perihelia above the ecliptic), but is differently oriented. 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).

[edit] Physical characteristics

[edit] Size and magnitude

Orcus compared to Eris, Pluto, 2005 FY9, 2003 EL61, Sedna, Quaoar, Varuna, and Earth.
Enlarge
Orcus compared to Eris, Pluto, 2005 FY9, 2003 EL61, Sedna, Quaoar, Varuna, and Earth.

The absolute magnitude of Orcus is 2.3 (comparable with the 2.6 of another KBO, 50000 Quaoar). Using an assumed albedo of 0.09, Trujillo estimates its diameter to be approximately 1600 km, which makes Orcus the largest known plutino after Pluto/Charon and the sixth-largest known trans-Neptunian object, after Eris, Pluto, (136472) 2005 FY9, (136108) 2003 EL61 and 90377 Sedna.

[edit] Colours and spectra

Observations in infrared by the European Southern Observatory give results consistent with mixtures of water ice and carbonaceous compounds. Further, the infrared spectra taken with the Gemini telescope confirmed a modest water ice signature, compatible with a cover of 15–30%, but no more than 50% of the surface. This means there is less ice than on Charon, but a similar amount to that on Triton. Limitations were also placed on the amount of methane ice (less than 30%) leaving open the possibility for discovery of other components in the future.

KBOs display a diversity of colours and spectra even among objects with similar orbits. Orcus presents a neutral colour in comparison with the redness of an object like Ixion.

[edit] Name

Under the guidelines of the International Astronomical Union's 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, a god of the dead in Roman mythology. The name was approved and published on November 22, 2004.

[edit] External links and sources

[edit] References

  1. ^ Tegler, Stephen C. (2006-01-26). Kuiper Belt Object Magnitudes and Surface Colors. Retrieved on 2006-11-05.
  • C. de Bergh, A. Delsanti, G. P. Tozzi, E. Dotto, A. Doressoundiram and M. A. Barucci (2005). "The Surface of the Transneptunian Object 9048 Orcus". TAstronomy & Astrophysics 437: 1115-1120. Abstract
  • Chadwick A. Trujillo, Michael E. Brown, David L. Rabinowitz, Thomas R. Geballe (2005). "Near Infrared Surface Properties of the Two Intrinsically Brightest Minor Planets (90377) Sedna and (90482) Orcus". The Astrophysical Journal 627: 1057–1065. Preprint on arXiv.


Minor planets
Previous minor planet 90482 Orcus Next minor planet



 v  d  e 
Trans-Neptunian objects
Plutinos : Pluto* | 1993 RO | 1993 RP | 1993 SB | 1993 SC | 1994 TB | 1995 QZ9 | 1996 SZ4 | 1996 TP66 | 38083 Rhadamanthus | 1999 TC36 | 38628 Huya | 28978 Ixion | 2002 VR128 | 2003 VS2 | 90482 Orcus | Unnumbered: 2003 AZ84

Cubewanos: 1992 QB1 | 1994 GV9 | 1994 JQ1 | 1994 VK8 | 1996 TO66 | 58534 Logos| 1998 WW31 | 19521 Chaos | 53311 Deucalion | 20000 Varuna | 2001 KP77 | 2002 AW197 | 50000 Quaoar | 2002 MS4 | 2002 TX300 | 2002 UX25 | 2003 EL61 | 2004 GV9| 2005 FY9 | Unnumbered: | 2003 MW12 | 2003 QW90 | 2005 RN43

Twotinos: 2002 WC19 | 1996 TR66 | Unnumbered: 1998 SM165 | 1997 SZ10 | 1999 RB216 | 2000 JG81

Scattered disc objects: Eris* | 1995 TL8 | 1996 GQ21 | 1996 TL66 | 1999 DE9 | 2000 OO67 | 2000 OM67 | 2001 KC77 | 2001 UR163 | 2002 CY224 | 2002 GX32 | 2002 RP120 | 2002 TC302 | 90377 Sedna** Unnumbered: 2000 CR105 | 2000 EE173 | 2004 XR190 | 2005 TN74

Unclassified Objects : 1994 JS | 1994 JR1 | 1995 DA2 | 1995 SM55 | 1996 TQ66 | 1997 CR29 | 1997 CS29 | 1997 CU29 | 1997 QJ4 | 1998 HJ151 | 1998 HK151 | 1998 HP151 | 1998 HM151 | 1998 KR65 | 1998 SM165 | 1998 SN1651998 US43 | 1998 VG44 | 1998 WW24 | 1998 WA31 | 1998 WU31 | 1998 WA25 | 1999 CP133 | 1999 CL158 | 1999 CC158 | 1999 DF9 | 1999 HT11 | 1999 HB12 | 1999 HC12 | 1999 KR16 | 1999 OY3

Natural satellites : Charon (Pluto) | Hydra (Pluto) | Nix (Pluto) | Dysnomia (Eris) | S/2000 (1998 WW31) 1 | S/2005 (2003 EL61) 1 | S/2005 (2003 EL61) 2 | (58534) Logos I Zoe

* - Also classified as a dwarf planet   ** - Currently classified as an SDO, though may be part of the Inner Oort Cloud
 v  d  e 
Large trans-Neptunian objects
Kuiper belt: Orcus | Pluto (Charon) | Ixion | 2002 UX25 | Varuna | 2002 TX300 | 2003 EL61 | Quaoar | 2005 FY9 | 2002 AW197
Scattered disc: 2002 TC302 | Eris | 2004 XR190 | Sedna
 See also Triton, astronomical objects and the solar system's list of objects, sorted by radius or mass
For pronunciation, see: Centaur and TNO pronunciation.
 v  d  e 
Small Solar System bodies
Vulcanoids | Near-Earth asteroids | Main belt | Jupiter Trojans | Centaurs | Damocloids | Comets | Trans-Neptunians (Kuiper belt · Scattered disc · Oort cloud)
For other objects and regions, see: asteroid groups and families, binary asteroids, asteroid moons and the Solar system
For a complete listing, see: List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names.