90377 Sedna

[taixyz1992]

For other uses, see Sedna (disambiguation).
90377 Sedna

Discovery image of Sedna (identified by the yellow arrow)
Discovery[1]
Discovered by Michael E. Brown,
C. Trujillo,
D. Rabinowitz
Discovery date November 14, 2003
Designations
MPC designation 90377 Sedna
Pronunciation /ˈsɛdnə/ SED-nə
Named after Sedna
Alternate name(s) 2003 VB12
Minor planet
category Trans-Neptunian object
detached object[2]
Orbital characteristics[3]
Epoch 2010-Jul-23 (JD 2455400.5)
Aphelion 1.437 × 1014 m
(960.78 AU)
Perihelion 1.142 3 × 1013 m
(76.361 AU)
Semi-major axis 7.757 6×1013 m
(518.57 AU)
Eccentricity 0.8527
Orbital period around 4,313,319 d
(11,809 yr)
Average orbital speed 1.04 km/s
Mean anomaly 358.01°
Inclination 11.927°
Longitude of ascending node 144.26°
Argument of perihelion 311.02°
Physical characteristics
Dimensions 1,200–1,600 km[4]
<1,600 km[5]
Mass 1.8–4.3 x 1021 kg[a]
Mean density 2.0? g/cm3[a]
Equatorial surface gravity 0.33–0.50 m/s2
Escape velocity 0.62–0.95 km/s
Sidereal rotation
period 0.42 d (10 h)[3][6]
Albedo 0.16–0.30[4]
Temperature ~12 K (see note w here)
Spectral type (red) B-V=1.24; V-R=0.78[7]
Apparent magnitude 21.1[8]
20.5 (Perihelic)[9]
Absolute magnitude (H) 1.58[3]
90377 Sedna is a trans-Neptunian object, discovered in 2003, which currently lies about three times as far from the Sun as Neptune. However, its farthest orbital distance from the Sun is estimated to be 960 astronomical units (AU), and thus it is, for the majority of its orbit, the most distant known object in the Solar System after long-period comets.[b]
Roughly two-thirds the size of Pluto, Sedna is hypothetically large enough to be rounded by its own gravity, and thus would qualify as a dwarf planet under current definitions. However, its distance from the Sun makes determining its shape difficult. Spectroscopy has revealed that Sedna's surface composition is similar to that of some other trans-Neptunian objects, being largely a mixture of water, methane and nitrogen ices with tholins. Its surface is one of the reddest in the Solar System.
Sedna's exceptionally long and elongated orbit, taking approximately 12,000 years to complete, and distant point of closest approach to the Sun, at 76 AU, have led to much speculation as to its origin. The Minor Planet Center currently places Sedna in the scattered disc, a group of objects sent into highly elongated orbits by the gravitational influence of Neptune. However, this classification has been contested, as Sedna never comes close enough to Neptune to have been scattered by it, leading some astronomers to conclude that it is in fact the first known member of the inner Oort cloud. Others speculate that it might have been tugged into its current orbit by a passing star, perhaps one within the Sun's birth cluster, or even that it was captured from another star system. Another hypothesis suggests that its orbit may be evidence for a large planet beyond the orbit of Neptune. Astronomer Mike Brown, who co-discovered Sedna as well as the dwarf planets Eris, Haumea, and Makemake, believes it to be the most scientifically important trans-Neptunian object found to date, as understanding its peculiar orbit is likely to yield valuable information about the origin and early evolution of the Solar System.[10]



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