Ceres (dwarf planet)

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Ceres  

Ceres
Discovery
Discovered by: Giuseppe Piazzi
Discovery date: January 1, 1801
Orbital characteristics
Epoch November 26, 2005
(JD 2453700.5)[1]
Aphelion 447,838,164 km
2.987 AU
Perihelion: 381,419,582 km
2.544 AU
Semi-major axis: 414,703,838 km
2.765 956 424 AU[2]
Eccentricity: 0.07976017[2]
Orbital period: 1679.819 days
4.599 years
Avg. orbital speed: 17.882 km/s
Mean anomaly: 108.509°
Inclination: 10.586712°[2]
Longitude of ascending node: 80.40696°[2]
Argument of perihelion: 73.15073°[2]
Physical characteristics
Equatorial radius: 487.3 ± 1.8 km[3]
Polar radius: 454.7 ± 1.6 km[3]
Flattening: 0.067 ± 0.005
Mass: 9.46 ± 0.04×1020 kg[4][5]
Mean density: 2.08 g/cm³[3]
Equatorial surface gravity: 0.27 m/s²
0.028 g
Escape velocity: 0.51 km/s
Sidereal rotation period: 0.3781 d
9.074 h[6]
Albedo: 0.113 (geometric)[7]
Surface temp.:
   Kelvin
min mean max
~167 K[8] 239 K[8]
Spectral type: G[9]
Apparent magnitude: 6.7 to 9.32
Absolute magnitude: 3.34[7]
Angular size: 0.84"[10] to 0.33"

Ceres (IPA: /ˈsɪəriz/, Latin: Cerēs), also known as 1 Ceres, is the smallest dwarf planet in the Solar System and the only one in the main asteroid belt. It was discovered on January 1, 1801, by Giuseppe Piazzi,[11] and is named after the Roman goddess Ceres—the goddess of growing plants, the harvest, and of motherly love. After about 200 years from its discovery, the International Astronomical Union decided to upgrade Ceres from an asteroid (or minor planet) to dwarf planetary status in 2006.

With a diameter of about 950 km, Ceres is by far the largest and most massive object in the asteroid belt, and has about a third of the belt's total mass. Recent observations have discovered that the asteroid is spherical, unlike the irregular shapes of smaller bodies with lower gravity. At its brightest it is still too dim to be seen with the naked eye.[12]

On September 27, 2007, NASA launched the Dawn Mission space probe to explore Ceres and Vesta.

[change] See also

[change] References

  1. ↑ Ted Bowell, Bruce v (January 2, 2003). Asteroid Observing Services. Lowell Observatory. Retrieved on 17 January 2007.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Yeomans, Donald K. (July 5, 2007). 1 Ceres. JPL Small-Body Database Browser. Retrieved on 5 July 2007.—The listed values were rounded at the magnitude of uncertainty (1-sigma).
  3. ↑ 3.0 3.1 3.2 Thomas, P.C, Parker J.Wm.; McFadden, L.A.; et.al. (2005). "Differentiation of the asteroid Ceres as revealed by its shape". Nature 437: 224-226. DOI:10.1038/nature03938.
  4. ↑ Pitjeva, E.V. (2005). "High-Precision Ephemerides of Planets—EPM and Determination of Some Astronomical Constants" (PDF). Solar System Research 39 (3): 176. DOI:10.1007/s11208-005-0033-2.
  5. ↑ D. T. Britt et al Asteroid density, porosity, and structure, pp. 488 in Asteroids III, University of Arizona Press (2002).
  6. ↑ Harris, A. W.; Warner, B.D.; Pravec, P.; Eds. (2006). Asteroid Lightcurve Derived Data. EAR-A-5-DDR-DERIVED-LIGHTCURVE-V8.0.. NASA Planetary Data System. Retrieved on 15 March 2007.
  7. ↑ 7.0 7.1 Tedesco, E.F.; Noah, P.V.; Noah, M.; Price, S.D. (2004). IRAS Minor Planet Survey. IRAS-A-FPA-3-RDR-IMPS-V6.0.. NASA Planetary Data System. Retrieved on 15 March 2007.
  8. ↑ 8.0 8.1 Saint-Pé, O., Combes, N.; Rigaut F. (1993). "Ceres surface properties by high-resolution imaging from Earth". Icarus 105: 271-281. DOI:10.1006/icar.1993.1125.
  9. ↑ Neese, C.; Ed. (2005). Asteroid Taxonomy.EAR-A-5-DDR-TAXONOMY-V5.0.. NASA Planetary Data System. Retrieved on 15 March 2007.
  10. ↑ Ceres Angular Size @ Feb 2009 Opposition: 974km dia / (1.58319AU * 149 597 870km) * 206265 = 0.84"
  11. ↑ Piazzi, Giuseppe (1801). Risultati delle osservazioni della nuova Stella scoperta il dì 1 gennajo all'Osservatorio Reale di Palermo (in Italian). 
  12. ↑ Ceres at Solarviews.com
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