Dimorphos

Dimorphos is a satellite asteroid of the larger asteroid Didymos. The two asteroids comprise a binary asteroid system within the solar system, with Dimorphos accounting for roughly 1% of the mass of the system.

Properties

Dimorphos is roughly 160 meters (520 feet) in diameter. It orbits Didymos every 11.9 hours, with an orbital radius of approximately 1.2 kilometers (0.7 miles). As such, it has an orbital speed of about 17 centimeters per second relative to Didymos.

References

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

Info from the European Space Agency (ESA): https://www.esa.int/Safety_Security/Hera/Target_asteroid2

Johnston, Wm. Robert. "(65803) Didymos and Dimorphos" Oct 9, 2021. Johnston's Archive [ http://www.johnstonsarchive.net/astro/astmoons/am-65803.html ]