90482 Orcus
Encyclopedia : 9 : 90 : 904 : 90482 Orcus
| Orbital elements | |
|---|---|
| Eccentricity (orbit)>e | |
| Inclination>i | ° |
| Perihelion>q |
|
| Argument of perihelion>ω | ° |
| Semi-major axis>a | AU |
| Longitude of the ascending node>ω | ° |
| Aphelion>Q |
|
| Mean anomaly>M | ° |
| Orbital period>P | years |
| Mean motion>n | °/day |
| Time of perihelion passage>TP | |
Orbit
Orcus is a typical plutino. Although at one point1 it approaches Neptune’s orbit, the orbital resonance keeps an angular separation of more than 60 deg between the two bodies.
Orcus and Pluto follow similar but differently oriented orbits as shown on the diagram (Orcus in blue, Pluto in red, Neptune in grey, positions as of April 2006). Both perihelia are above the ecliptic. Orcus is approaching the aphelion (2019) while Pluto has passed the perihelion (1989) and is descending toward the ecliptic.
1Orcus’s perihelion is ~30.7AU to be compared with Neptune’s axis of 30.07 but the perihelion is not the closest point of the two orbits as it is situated well above the ecliptic.
Size and magnitude
The absolute magnitude of the object is 2.3 to compare with 2.6 for 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 and the sixth-largest discovered KBO, after 2003 UB313, Pluto, 2005 FY9, 2003 EL61 and 90377 Sedna.Physical characteristics
Observations in infrared by ESO give results consistent with mixtures of water ice and carbonaceous compounds. Further, the infrared spectra taken with Gemini telescope confirmed a modest water ice signature, compatible with a cover of 15–30%, but no more than 50% of the surface. It is less than found on Charon, but similar to 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.The diversity of colours and spectra even for objects following currently similar orbits is puzzling. Orcus presents a neutral colour as opposed to the second largest known plutino, Ixion (<820km) which is red, had no water ice discovered so far and has albedo higher than Orcus.
Name
Since it shares a similar size and orbit to that of Pluto, it too must be named after a deity of the underworld. In accordance with International Astronomical Union astronomical naming conventions, the discoverers' suggested name of Orcus was approved and published November 22, 2004. Orcus is both another name for the Greek deity Hades and a separate god of the dead in Roman mythology.Possible satellite
A recent proposal for Hubble Space Telescope observations submitted by Michael Brown mentions, in the abstract, "the Pluto-Charon analog system of Orcus and its satellite", which indicates that Orcus has a large satellite.External links and sources
- [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 F. Helin and Robert Thicksten / NEAT
- [MPEC 2004-D13] correcting MPEC 2004-D09
- [Chad Trujillo's page on 2004 DW]
- [First BBC article]
- [First New Scientist article]
- [Updated orbital elements from Lowell Observatory]
- [AstDys] orbital elements
- [Orbit simulation] from JPL (Java).
References
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| Trans Neptunian Objects [[http://encycl.opentopia.com/ edit ]] | |||||||
|---|---|---|---|---|---|---|---|
| Planet : Pluto | 2003 UB313 Plutino : Pluto* | 1993 RO | 1993 RP | | 1993 SC | 1994 TB | 1995 QZ9 | 1996 SZ4 | 1996 TP66 | 38083 Rhadamanthus | 38628 Huya | 28978 Ixion | 2003 VS2 | 90482 Orcus Cubewanos: 1992 QB1 | 1994 GV9 | 1994 JQ1 | 1994 VK8 | 1996 TO66 | 19521 Chaos | 53311 Deucalion | 2002 AW197 | 50000 Quaoar | 2002 MS4 | 2002 TX300 | 2002 UX25 | 1997 CQ29 = 58534 Logos | 2003 AZ84 | 2003 EL61 | 2003 QW90 | 2005 FY9 Twotino: 1996 TR66 | 1998 SM165 | 1997 SZ10 | 1999 RB216 | 2000 JG81 Scattered disk object: 1995 TL8 | 1996 GQ21 | 1996 TL66 | 2000 OO67 | 2000 OM67 | 2001 KC77 | 2001 UR163 | 2002 CY224 | 2002 GX32 | 2003 UB313** 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 WW31 | 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) | S/2000 (1998 WW31) 1 | S/2005 (2003 EL61) 1 | S/2005 (2003 EL61) 2 | S/2005 (2003 UB313) 1 |}
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