Is Vesta A Giant Asteroid Or A Protoplanet? Damned If I Know!

Straight-up: I don’t know the definition of a protoplanet, but people who do aren’t sure if the largest asteroid we’ve visited happens to be one.

io9:

Giant asteroid Vesta is so enormous, many astronomers don’t even refer to it as an asteroid, preferring to call the celestial body a “protoplanet.” This image, which compares Vesta to eight other asteroids that we’ve sent spacecraft to investigate, helps illustrate the reason such a distinction exists.

A hi-res version of the image up top (one where you can actually see 25143 Itokawa) is available  here.

At roughly 330 miles in diameter, Vesta is not only the largest asteroid we’ve ever visited (NASA’s Dawn spacecraft  has been orbiting Vesta since July), it’s nearly the largest asteroid in our entire Solar System. Second in size only to  Ceres, the two bodies are estimated to account for over 40% of the mass  in the entire  main asteroid belt.

Dawn, which recently  maneuvered into its closest orbit  around Vesta, is scheduled to continue investigating the protoplanet until the middle of 2012, when it will set course for Ceres. By investigating these massive celestial bodies, scientists hope to acquire a better understanding of what conditions were like during our Solar System’s infancy.

Two bodies counting for 40% of the mass in in the main asteroid belt? Talk about hogging it the fuck  up.