Instead of driving onward to Jupiter in our tour of the solar system, we are instead going take a quick pit stop at Ceres. Ceres is a one of the little oddballs of our solar system. This almost spherical asteroid was discovered in 1801 by Giuseppe Piazzi. Piazzi was among a group of 24 astronomers that set out on a search for a planet thought to exist between that gap between Mars and Jupiter.
What he found was a tiny speck of of light in the sky and over a period of time Piazzi was able to plot its course and determine and orbit for this little object. Debate raged over the the ensuing years as to whether this little 950 km diameter object was a planet, asteroid, or comet.
Piazzi himself was pretty sure the he has discovered a comet, as he wrote about it in a series of letters to a fellow astronomer. Early on, Ceres was designated as a planet and it appeared as such in the literature of the day. As it became apparent that the solar system is littered with objects just like Ceres, astronomers backed off on planetary status for Ceres and it was relegated to being called an asteroid. In recent years, the status of Ceres was revisited in light of the controversy over the planetary status of Pluto. Ceres is either mentioned as an asteroid or dwarf planet in todays astronomy literary circles.
NASA launched the Dawn mission towards Ceres in 2007. The Dawn probe made a couple of wide loops around the sun and got a gravity assist by slinging itself around Mars to reach Vesta, the largest known asteroid in our solar system. This spacecraft is currently maintaining an orbit at Vesta. In 2012, it will use its ion drive and push itself outwards to match the orbit of Ceres. Dawn is expected to reach Ceres in 2015,to provide some closeup images.
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