Largest Asteroid in the Solar System
Written by Fraser Cain
The largest asteroid in the Solar System isn't an asteroid any more. I know, this all sounds a little confusing.
Okay, a few years ago, the largest asteroid was Ceres, with a diameter of 950 km. But in 2006, the International Astronomical Union redefined the term planet. At that point, Pluto was no longer a planet, but now it was a dwarf planet. The asteroid Ceres and the newly discovered Kuiper Belt object Eris also became dwarf planets. Since Ceres is now a dwarf planet, what's the largest asteroid?
That distinction falls to Vesta. It's the second most massive object in the asteroid belt (after Ceres), but it's actually classified as an asteroid. Vesta measures 530 km across, and contains about 9% of the total mass of the entire asteroid belt.
Vesta was discovered in 1807 by the German astronomer Heinrich Wilhelm Olbers, and it was named after the Roman goddess of home and hearth. Astronomers think that Vesta has a metallic iron-nickel core, with an overlying rocky olivine mantle and a surface crust.
NASA's Dawn spacecraft will reach Vesta in 2010, and orbit the asteroid for 9 months before flying off to Ceres and other objects in the asteroid belt.
Here's an article about how Vesta formed fast and early in the Solar System, and some Hubble images of the asteroid.
Here's more on Vesta from Solar Views, and some images from NASA.
We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.
Filed under: Astronomy
