https://www.theregister.co.uk/2020/01/10/lucy_nasa_eurybates_asteroid/

A relatively small rock was spotted orbiting asteroid Eurybates this month by scientists using the Hubble Space Telescope. Luckily enough, that's the same asteroid NASA's Lucy probe is aiming to fly past and inspect in 2027, so boffins will be able to get a closer look at both.

Eurybates is one of the Trojan asteroids, a cloud of cosmic boulders between the Sun and Jupiter that are held in a stable position. Eggheads first observed Eurybates with Hubble in 2018, and the existence of its natural satellite wasn't suspected until November 2019, when a Lucy team member clocked something odd in the asteroid's readings.