Complex sentence: Asteroid is the smallest solar system object ever studied in detail and with a rotational period of 10.7 minutes, was the fastest spinning object observed at the time of its discovery; most asteroids with established rotational rates have periods measured in hours.
Split into simpler sentences: Asteroid is the smallest solar system object ever studied in detail and was the fastest spinning object observed at the time of its discovery. Most asteroids with established rotational rates have periods measured in hours.