* Astronomy

Daniel Kirkwood (September 27, 1814 - June 11, 1895) was an American astronomer.
Kirkwood's most significant contribution came from his study of asteroid orbits. When arranging the then-growing number of discovered asteroids by their distance from the Sun, he noted several gaps,[2] now named Kirkwood gaps in his honor, and associated these gaps with orbital resonances with the orbit of Jupiter. Further, Kirkwood also suggested a similar dynamic was responsible for Cassini Division in Saturn's rings, as the result of a resonance with one of Saturn's moons. In the same paper, he was the first to correctly posit that the material in meteor showers is cometary debris.
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