The Astéroïde (90482) Orcus was discovered the February 17th 2004 by Michael E. Brown, Chadwick Trujillo and David L. Rabinowitz. It is a member of the Ceinture of Kuiper.
With a diameter estimated at 1 600 km, it is one of largest the known objects transneptuniens. It is in orbital Résonance 3:2 with Neptune and is thus a Plutino.
Its magnitude is considered at 18,5, similar to that of (50000) Quaoar. Orcus being moved away more, with an average distance from 39,473 ua, it should be larger than this last.
Orcus was to bear the name of a divinity of the Hells, because its orbit and its size are comparable with those of Pluton. The discoverers proposed Orcus , which was adopted and promulgated the November 22nd 2004. Orcus is at the same time another name of the Greek god Hadès and a distinct Roman infernal divinity. J.R.R. Tolkien would have drawn the name from the bad creatures of the Seigneur of the Rings , the orc S ( Orcs in English), of that of Orcus.
Orbits
Orcus is the larger second Plutino (in orbital Résonance 2:3 with Neptune, like Pluton). Although it approaches the orbit of Neptune to a point1, resonance maintains a separation angular of more than 60 degrees between the two objects. Orcus follows an orbit similar to that of Pluto but differently directed as shown on the diagram (Orcus in blue, Pluton in red, Neptune in gray, the positions in April 2006). The Périhélie S of the two objects are located above the ecliptic . Orcus approaches its Aphélie (in 2019) while Pluton passed already its perihelion and goes down towards the ecliptic.1Orcus approaches the Sun with ~30.7ua (to be compared with the axis of Neptune of 30.07) but its perihelion is not the point nearest to the two orbits as it is located well above the écliptique.
The moon
The moon of approximately 220km has just been discovered at 0.25 seconds of arc of the transneptunien.
See too
Internal bonds
- Plutino
- (28978) Ixion
- Belt of Kuiper
- Object transneptunien
External bonds
- MPEC 2004-D09 announcing the discovery, allotted 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
- Page of Chad Trujillo on (90482) Orcus
- Applet of visualization of the orbits (Java)
Be-X-old: Аркус
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