Asteroid Ceres
Written by Jerry Coffey
Ceres as seen by the Hubble Space Telescope in 2004 (HST)
Ceres is the largest asteroid in the Solar System, orbiting at an average distance of 413 million km from the Sun. Ceres was discovered on New Years Day in 1801 by Giuseppe Piazzi, a monk and astronomer in Sicily, and the founding director of the Palermo Astronomical Observatory. Ceres was discovered using the Titius-Bode Law that predicts the position of planets based on a mathematical equation of their distance from the Sun. This law predicted the position of Uranus and led to the false belief that Ceres was a planet. Today, Ceres falls into the new classification of dwarf planet.
Ceres is by far the largest and most massive asteroid in the belt between Mars and Jupiter. It's approximately the size of Texas or 975 km by 909 km with a mass of 9.5 x 1020 kg. It actually represents 1/3 of all of the mass of the asteroid belt. It has enough mass to pull itself into a sphere; a major requirement to be considered a dwarf planet. Ceres revolves around the sun every 1679.819 days with a very small axial tilt. The surface is relatively warm. The high temperature is thought to be in the neighborhood of -38°C (235 K). Ceres has a visual brightness magnitude of +6.9 to +9. When it is at the brightest point possible, Ceres is nearly bright enough to be seen with the unaided eye. It can be seen with binoculars, however, whenever it's above the horizon on a completely dark night.
The Dawn space mission is scheduled to visit Ceres in 2015 after stopping by Asteroid Vesta in 2011. There had been some problems with Dawn's ion propulsion system, but it was reignited on June 8, 2009. As of June 15, 2009 (when this article was written), Dawn was only 801 days away from Vesta on its way to Ceres. This space mission hopes to be the first to orbit and observe two planetary bodies, and will make space exploration history if successful.
Although Ceres has not been considered a planet for a very long time, it generates a great deal of interest. The easy visibility of the asteroid and the dark and light spots on its surface make it great fodder for amateur astronomers and their professional counterparts, alike. Hopefully, the upcoming orbital evaluation of Ceres by the Dawn space mission will clear some of the mystery. Whatever the outcome, Giuseppe Piazzi presented astronomers with quite a bit of excitement over the last 200 years.
We have written many articles about Ceres for Universe Today. Here's an article about how Ceres could be the root of life in the Solar System. And here's an article about how there could be liquid water on Ceres.
Want more resources on asteroids? Here's NASA's Lunar and Planetary Science Page on asteroids. And here's NASA's World Book on Asteroids.
We have recorded two episodes of Astronomy Cast about asteroids. There's Episode 55: The Asteroid Belt, and here's Episode 29: Asteroids Make Bad Neighbors.
Filed under: Astronomy
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