Tidal forces - Comet Shoemaker/Levy
1993 comet noticed
- broken into ~ 26 fragments HST image
- Orbiting around Jupiter
- must have been captured by Jupiter sometime in past
- Passed too close to Jupiter, and tidal forces ripped nucleus apart
- recall tides on Earth
- tidal bulges from Moon’s tidal force board
- When tidal force exceeds self-gravity, object can be ripped apart
- The distance of approach for this to happen called the Roche limit, which is about 2 times the radius of a planet
- Explains why major satellites are invariably found outside the Roche limit
- inside the Roche limit are found rings (i.e. Saturn, Jupiter, Neptune, and Uranus) -- remains of objects ripped apart
- spacecraft can safely go inside the Roche limit
- held together by chemical forces (bolts, etc.), not gravity