Planet
The smallest known planet is PSR B1257+12A, one of the first extrasolar planets discovered, which was found in 1992 in orbit around a pulsar. Its mass is roughly half that of the planet Mercury. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b, with a mass (and radius) slightly higher than that of the Moon.
73 Klytia
Klytia ( ; minor planet designation: 73 Klytia) is a main-belt asteroid. It was the second and last asteroid discovery by the prolific comet discoverer Horace Tuttle, on April 7, 1862. It is named after Clytia, who loved Apollo in Greek mythology. Of the first one hundred numbered asteroids, Klytia is the smallest.