Neptune has a new moon, and it’s also the gas giant’s smallest to date — only a little over 20 miles across. The brand new satellite is called Hippocamp.

Astronomers led by Mark Showalter of the SETI Institute discovered it using the Hubble Space Telescope combined with an innovative method to track dim and tiny objects as they orbit.

Because the object is so tiny, there’s still a lot astronomers don’t know about Hippocamp, named after a Greek sea monster in keeping with Neptune’s naut