Dawn Arrives at Ceres

March 2015  :  Francine Jackson

Can you believe it’s been four years since we first started thinking Vesta Fiesta, when little space craft Dawn approached, then began to orbit, our fourth discovered asteroid, Vesta? After one year of discovery, we have images of this bright member of the asteroid belt such as could never have been gotten from Earthbound telescopes. 

And, now, the scene has shifted. After a three-year voyage through the asteroid region, Dawn is now ready to begin another yearlong session, at what is now one of our five dwarf planets: Ceres, the first discovered in this region, and the largest within this part of our solar system.

Ceres was first observed in 1801 by Guiseppe Piazzi, who believed he had found the “missing” planet, the object that closed the mathematics chart first proposed by Titius of Wittenberg in 1766. But, then, other objects became known within that separation between Mars and Jupiter – the next three also by telescope, then the explosion of discoveries courtesy of photography. Although Ceres continued to be the largest body found there, its diameter was too small to keep the title of planet, so it became known, at about 590 miles in diameter, as the largest asteroid, at least until last decade, when it became promoted to dwarf status. 

Already the images are flowing from Ceres. Dawn has arrived at the vicinity, and is working toward mapping the entire body, much as it did with Vesta. In addition to its topographic mapping, Dawn is equipped with instrumentation to measure its gravitational field, its mineralogical composition, and any gamma ray and neutron presence. It is hoped the exploration of Ceres will be another step forward in our knowledge of the beginning of our solar system.