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.
List of slow rotators (minor planets)
The periods given in this list are sourced from the "Light Curve Data Base" (LCDB), which contains lightcurve data for more than 15,000 bodies. Most minor planets have rotation periods between 2 and 20 hours. , a group of approximately 650 bodies, typically measuring 1–20 kilometers in diameter, have periods of more than 100 hours or 4 days. Among the , there are currently 14 bodies with a period longer than 1000 hours. According to the Minor Planet Center, the sharp lower limit of approximately 2.2 hours is due to the fact that most smaller bodies are thought to be rubble piles – conglomerations of smaller pieces, loosely coalesced under the influence of gravity – that fly apart if the period is shorter than this limit. The few minor planets rotating faster than 2.2 hours, therefor, can not be merely held together by self-gravity, but must be formed of a contiguous solid.