Sedna – Our Solar System Planet No_10





90377 Sedna is a trans-Neptunian object and a likely dwarf planet discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. It is currently 88 AU from the Sun, about three times as distant as Neptune.
For most of its orbit Sedna is farther from the Sun than any other known dwarf planet candidate. Sedna has a highly elliptical orbit, with its aphelion estimated at 975 AU and its perihelion at about 76.16 AU. At its discovery it was approaching perihelion and about 89.6 AU from the Sun. At the time of its discovery it was the most distant object in the solar system yet observed; although the orbits of some objects—like long-period comets—extend farther than that of Sedna, they are basically too dim to be observed except near perihelion. Eris was later detected at 97 AU.
Sedna’s precise orbital period is not yet known, but it is calculated at between 10.5 and 12.0 thousand years. It should reach perihelion in late 2075 to mid 2076. Sedna will overtake Eris as the farthest known spheroid orbiting the Sun in 2114. When first discovered, Sedna was believed to have an unusually long rotational period (20 to 50 days). A search was thus made for a natural satellite, the most likely cause for such a long rotation, but investigation by the Hubble Space Telescope in March 2004 observed no such object orbiting the planetoid. New measurements from the MMT telescope suggest a much shorter rotation period, only about 10 hours, rather typical for bodies of its size.

Discovered by M. Brown,
C. Trujillo,
D. Rabinowitz
Discovery date November 14, 2003
MPC designation 90377 Sedna
Pronunciation /ˈsɛdnə/ SED-nə
Alternate name(s) 2003 VB12
Minor planet
category Trans-Neptunian object
detached object
Orbital characteristics
Epoch September 26, 1990 (JD 2 448 160.5)
Aphelion 1.459 × 1014 m (975.56 AU)
Perihelion 1.139 3 × 1013 m (76.156 AU)
Semi-major axis 7.866 8×1013 m (525.86 AU)
Eccentricity 0.855
Orbital period around 4,404,480 d (12,059.06 a)
Average orbital speed 1.04 km/s
Mean anomaly 357.457°
Inclination 11.934°
Longitude of ascending node 144.514°
Argument of perihelion 311.123°
Physical characteristics
Dimensions 1,2001,600 km
Mass 8.3 × 10207.0 × 1021 kg, (0.050.42 Eris)
Mean density 2.0? g/cm³
Equatorial surface gravity 0.330.50 m/s²
Escape velocity 0.620.95 km/s
Sidereal rotation period 0.42 d (10 h) 1
Albedo 0.160.30[3]
Temperature below 33 K
Spectral type (red) B-V=1.24; V-R=0.78
Apparent magnitude 21.1
20.4 (Perihelic)[8]
Absolute magnitude (H) 1.56

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Originally posted 2010-12-10 13:43:14. Republished by Blog Post Promoter

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