Okay, I cheated.  It’s not the birthday of Ceres, it’s the anniversary of the discovery of Ceres, January 1st, 1801, by Guiseppe Piazzi.  Piazzi was looking for a star when he found Ceres, and initially thought it might be a comet (but had his suspicions he had discovered “something better”).

Named “Ceres” after the Roman goddess of motherly love and the harvest, Ceres is the largest object in the asteroid belt.  With a diameter of 590 miles, it contains fully a third of the belt’s mass.

Ceres (bottom left) to scale.  Image:  NASA/JPL

Ceres is believed to have a rocky core, overlaid by a thick mantle of water ice about 100 km thick.  That would mean that Ceres is carrying around about 200 million cubic km of water, more than the volume of fresh water on the Earth.  This is difficult to confirm, because water ice on Ceres would be expected to sublimate (go directly from a solid to a gas, bypassing the liquid form… happens on Earth all the time) instead of evaporate.  Hopefully when the Dawn Space Probe reaches Ceres in 2015 we will find out for sure.  Ceres has a rotational period of 9 hours, 4 min, and an orbital period of 4.6 Earth years.  The orbit is inclined 10.6 degrees.  Once thought to be a member of the Gefion asteroid family, it has since been proven to have an uncommon origin.

Image:  NASA/ESA  Hubble Space Telescope images of Ceres.  Nature of the “white spot” is unknown.

Spectral analysis of Ceres has shown some very interesting indicators for iron-rich phyllosilicates, making it the third object in our solar system discovered to have carbonates (the other two are Earth and Mars).

I’m looking forward to 2015.

If you’re interested, this is a link to a research paper on the surface composition of Ceres, published in 2006.