The Panoramic Survey Telescope and Rapid Response System, or Pan-STARRS 1, is a 1.8 metre telescope with a 1.4 gigapixel camera mounted on it, constantly surveying the sky. It hunts stars, galaxies and also anything that moves from moment to moment, specifically comets, trans-Neptunian objects and asteroids. Now it has managed to capture an asteroid that may or may not pose a future hazard.
2010 STS3 is a 45 metre wide asteroid, capable of causing regional disruption on a par with the object believed responsible for the Tunguska explosion, which flattened trees after a similar sized object exploded in the atmosphere above the sparsely inhabited region.
The object poses no immediate risk, but as it is passing close to us, it will be monitored and its orbital parameter derived from dedicated follow up observations to help determine more precisely where it will be. Presently, there is a small chance of an impact in 2098, but the margin of error on the orbital parameters is too high to make any warnings relevant.
The main significance of 2010 ST3 was that Pan-STARRS saw it first, proving its ability to detect these things when they appear. Pan-STARRS 1 is set to be supplemented by Pan-STARRS 4, a larger, more sensitive observatory, which will assist in surveying the skies.