Ceres

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Ceres
Date of discovery January 1, 18011 January 1801
16 Teveth 5561 H
16 Teveth 5959 AM
Name of discoverer Giuseppe Piazzi
Name origin Roman goddess of agriculture
Orbital characteristics
Celestial class Dwarf planet
Primary Sun
Order from primary 5
Perihelion 2.545 AU380,726,579.15 km
236,572,528.403 mi
Aphelion 2.987 AU446,848,837.69 km
277,658,995.025 mi
Semi-major axis 2.765956424 AU413,781,189.543 km
257,111,711.072 mi
Titius-Bode prediction 2.8 AU
Orbital eccentricity 0.07976017
Sidereal year 4.599 a1,679.785 da
Avg. orbital speed 17.882 km/s64,375.2 km/h
11.111 mi/s
40,000.895 mph
Inclination 10.586712°0.185 rad
11.763 grad to the ecliptic
Rotational characteristics
Sidereal day 9.074 h0.378 da
Axial tilt 3°0.0524 rad
3.333 grad
Physical characteristics
Mass 9.46 * 1020 kg1.583e-4 M⊕
0.0129 M☾
Mean density 2,077 kg/m³2.077 g/ml
129.663 lb/ft³
Equatorial radius 487.3 km302.794 mi
Polar radius 454.7 km282.537 mi
Surface gravity 0.27 m/s²0.886 ft/s²
0.0275 g
Escape speed 0.51 km/s1,836 km/h
0.317 mi/s
1,140.838 mph
Surface area 11,151,000 km²4,305,425.17 mi²
0.0219 A⊕
0.294 A☾
Mean temperature 167 K-106.15 °C
-159.07 °F
300.6 °R
Maximum temperature 239 K-34.15 °C
-29.47 °F
430.2 °R
Number of moons 0
Composition Rock and water
Color #FFC9A0

Ceres is the first identified object in the asteroid belt, and the largest. Giuseppe Piazzi discovered it on January 1, 1801. Recently, in the wake of the Eris-Pluto controversy, the International Astronomical Union has declared that it is more than a mere asteroid and qualifies as a dwarf planet.

Contents

Discovery

Piazzi was searching for the "missing planet" that, according to Bode's law, should exist between Mars and Jupiter. Bode's law predicted an object having a semi-major axis of 2.8 AU, remarkably close to the actual semi-major axis of Ceres.

When Piazzi first observed Ceres, he thought he was looking at a comet. But comets normally move much faster than Ceres does, a fact Piazzi appreciated. He observed Ceres 24 times and reported his discoveries to Bode and other astronomers.

Shortly after the publication of Piazzi's findings, Ceres was lost in the glare of the sun. Karl Friedrich Gauss, then 24 years old, predicted Ceres' path and suggested where to look to reacquire Ceres. On December 31, 1801, the astronomer Baron von Zach found Ceres very near where Gauss said he might.

Status

For many years Ceres was listed as a planet, even after the asteroids Pallas, Juno, and Vesta were discovered. With the discovery of yet more objects in what would later be known as the Asteroid Belt, Ceres was reclassified as an asteroid, the largest of all such bodies. But Ceres, unlike any other object in the asteroid belt, has a hydrostatic-equilibrium shape, characteristic of an object sufficiently massive that its self-gravity forces such a shape despite the rigid-body forces that normally hold a solid object's shape.

In 2006, the discovery of Eris provoked a fresh look at all the bodies of the solar system, and in particular what constituted a planet and what didn't. As a result of the debate, Eris and Pluto, an object even smaller than Eris, were classed as dwarf planets—a new classification with definite criteria. Ceres meets these criteria, and thus Ceres is considered a dwarf planet—the smallest of three known bodies of that class.

Composition

Recent observations made by the Hubble Space Telescope suggest that Ceres might be very rich in water ice. Specifically, astronomers have concluded that Ceres has a layered interior, with a rocky inner core, a thick layer of water ice, and a dusty outer crust. McFadden specifically says that Ceres is an "embryonic planet," one that (according to evolutionary theory) tried to form a planet but could not because Jupiter, being so close, so perturbed the local gravitational field that Ceres could not grow any larger than it is. Findings supporting the water-ice theory include:

  1. Most objects having hydrostatic-equilibrium or round shape have differentiated, or layered, interiors.
  2. Spectrography of the surface shows evidence of water-bearing minerals.

Parker and his colleagues speculate that Ceres might be composed of 25% water and thus have more fresh water than in all the fresh-water sources on earth.

Satellites

Ceres has no known satellites.

References


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See also

Facts about CeresRDF feed
Apoapsis 446,848,837.69 km (2.987 AU, 277,658,995.025 mi)  +
Axial tilt 0.0524 rad (3 °, 3.333 grad)  +
Color #FFC9A0  +
Composition Rock and water  +
Date of discovery 1 January 1801  +
Discoverer Giuseppe Piazzi  +
Dwarf planet mass 9.46e+20 kg (1.583e-4 M⊕, 0.0129 M☾)  +
Dwarf planet surface area 11,151,000 km² (4,305,425.17 mi², 0.0219 A⊕, 0.294 A☾)  +
Equatorial radius 487.3 km (302.794 mi)  +
Escape speed 0.51 km/s (1,836 km/h, 0.317 mi/s, 1,140.838 mph)  +
Inclination 0.185 rad (10.587 °, 11.763 grad)  +
Maximum temperature 239 K (-34.15 °C, -29.47 °F, 430.2 °R)  +
Mean temperature 167 K (-106.15 °C, -159.07 °F, 300.6 °R)  +
Member of Dwarf planet  +
Orbital eccentricity 0.0798  +
Orbital speed 17.882 km/s (64,375.2 km/h, 11.111 mi/s, 40,000.895 mph)  +
Order 5  +
Periapsis 380,726,579.15 km (2.545 AU, 236,572,528.403 mi)  +
Planet density 2,077 kg/m³ (2.077 g/ml, 129.663 lb/ft³)  +
Polar radius 454.7 km (282.537 mi)  +
Primary Sun  +
Satellites 0  +
Semi-major axis 413,781,189.543 km (2.766 AU, 257,111,711.072 mi)  +
Sidereal day 9.074 h (0.378 da)  +
Sidereal period 1,679.785 da (4.599 a)  +
Surface gravity 0.27 m/s² (0.886 ft/s², 0.0275 g)  +
Titius-Bode prediction 2.8 AU  +
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