Today the minor planet 4 Vesta will pass through opposition.
4 Vesta is one of the largest objects orbiting between Mars and Jupiter, a region often referred to as the Asteroid Belt. This is the second largest asteroid, at 530km (329miles) in diameter. It is also usually the brightest asteroid that can seen by earthbound observers. When Vesta is at opposition it is bright enough to be just visible to the unaided eye, usually around 6th magnitude.
This year Vesta will reach magnitude 5.7 at opposition. This magnitude requires a dark site to view without the aid of a telescope. Precise knowledge of the location is also helpful. Given these two items it becomes possible to see an asteroid with the unaided eye.
The minor planet is currently located in Virgo about 2.5° northwest of τVir. Interestingly enough the dwarf planet 1 Ceres will be located about 2° east and a touch south of Vesta. Despite being much larger than Vesta it will be over a full magnitude dimmer at about 6.9 magnitude.
Vesta was visited by the Dawn spacecraft during 2011 and 2012. Dawn is now on course for Ceres with a planned rendevouz in February 2015.