Didymos

The asteroid Didymos and its smaller, satellite asteroid Dimorphos comprise a binary asteroid system within the solar system. Didymos was discovered in 1996, and is estimated to contain roughly 99% of the mass of the Didymos-Dimorphos system.

Properties

Didymos is only roughly spherical in shape, with an approximate diameter of 780 meters (slightly less than half a mile). It rotates about its axis about every 2.3 hours.

References

Info from NASA: https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/didymos/in-depth/