solar system

Orcus - 2004DW

Orcus is also know as DW2004 and is a large plutino (an object in 2:3 orbital resonance with Neptune). Orcus's 247 year orbit is shaped similarly to Pluto's .

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90482 Orcus (2004 DW)


Orcus is also know as DW2004 and is a large plutino (an object in 2:3 orbital resonance with Neptune).[2] Orcus's 247 year 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). Over a 14,000 year period Orcus stays more than 18 AU from Neptune.[9] Because their mutual resonance with Neptune constrains Orcus and Pluto to remain on opposite sides of the Sun in their otherwise very similar motions, Orcus is sometimes described as the "anti-Pluto".

A new planet in the outer Solar System was discovered on 17 February 2004 by an automated sky survey telescope in California. At present the planet is designated 2004 DW and was found by California Institute of Technology astronomers Chad Trujillo and Mike Brown, and David Rabinowitz of Yale University. The same team discovered the planet Quaoar in 2002

Physical characteristics

Physical characteristics
Discovered by M. Brown,
C. Trujillo,
D. Rabinowitz
Discovery date February 17, 2004
Alternate name 2004 DW
Minor planet category Plutino,
Plutoid candidate
Dimensions 946.3 +74.1-72.3 km (diameter)[4]
Mass ~7×1020 kg
Mean density ~1.6 g/cm³
(comparable to that of Charon)
Equatorial surface gravity ~0.2 m/s²
Escape velocity ~0.44 km/s
Rotation period 10.08 + 0.01 hr
Albedo 19.75 +3.40-2.76 %[4]
Temperature ~44 K[5]
Spectral type B-V=0.68; V-R=0.37
(neutral color)
Apparent magnitude 19.1 (opposition)[7][8]
Absolute magnitude 2.3

2004 DW could even be larger than Pluto's moon, Charon which is 1,300km (810 miles) across. It has an orbit that is much larger than Pluto's, being, on average, 2.4 billion km (1.5 billion miles) further out.

Astronomers believe that there are many more so-called "Kuiper Belt Objects" awaiting discovery in the cold, dark, outer reaches of the Solar System.

The Kuiper Belt (KB) is a region inhabited by small worlds of rock and ice. It is similar in some ways to the Asteroid Belt - a region of rocky debris between Mars and Jupiter. However, the KB contains a hundred times more material than all the asteroids put together.

About The Dwarf Planet

2004 DW Orcus One thing astronomers want to stress is that 2004 DW is not a major planet. Although it is probably slightly larger than half the size of Pluto, there are other objects of a similar size out there which do not, by the current definition, qualify as a planet.

But that is not to say that a new planet could not be found. Experts say there could be a Pluto-sized object lurking in the darkness awaiting discovery. 2004 DW could be a type of object called a "Plutino." Such objects have an orbit related to Pluto's path around the Sun.

Looking back in their archives astronomers have already picked up the new object in images taken in 2002. They will use this observation, and any others they may find further back, to determine its orbit more accurately.

90482 Orcus (2004 DW) Orbital characteristics

Orcus - DW 2004
Aphelion 7 188.17 Gm (48.05 AU)
Perihelion 4 535.80 Gm (30.32 AU)
Semi-major axis 5 862.44 Gm (39.188 AU)
Eccentricity 0.226 18
Orbital period 89 606 d (245.33 yr)
Average orbital speed 4.68 km/s
Mean anomaly 164.68°
Inclination 20.593°
Longitude of ascending node 268.722°
Argument of perihelion 72.474°
Satellites 1 (92-432 km)

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