Shoemaker-Levy 9: First of Its Kind
Shoemaker-Levy 9's (SL9) crash into Jupiter was the first time in the history of humankind that a comet and a planet were observed to collide. Amateur and professional astronomers, using every major telescope on Earth, viewed the impacts and recorded them. As the comet neared Jupiter, it began to speed up. Jupiter's powerful gravity then "captured" the comet, and it began orbiting the planet. Jupiter's gravitational tug was strongest on the part of the comet closest to the planet. This uneven gravitational force broke apart SL9.
An object moves faster when it comes close to the gravitational pull of another celestial object, such as a planet. If the object breaks up, the pieces stretch out into a line, just like the SL9 fragments. The piece closest to the planet experiences the greatest gravitational force. This fragment moves faster, and is the first to slam into the planet!