Free Astronomy Magazine May-June 2019

42 MAY-JUNE 2019 SPACE CHRONICLES by NASA/ESA Hubble helps uncover origin of Neptune’s smallest moon Hippocamp A team of astronomers, led by Mark Showalter of the SETI Institute, have used the NASA/ESA Hubble Space Telescope to study the origin of the smallest known moon orbiting the planet Neptune, discovered in 2013. “The first thing we realised was that you wouldn’t expect to find such a tiny moon right next to Neptune’s biggest inner moon,” said Mark T his artist’s animation shows how the smallest known moon of Neptune, now named Hippocamp, might look close up. In the animation the camera rotates once around the tiny moon, showing first the distant Sun and at the end the planet Neptune, which the moon is orbit- ing. [ESA/Hubble, L.Calçada] Showalter. The tiny moon, with an estimated diameter of only about 34 km, was named Hippocamp and is likely to be a fragment from Proteus, Neptune’s second-largest moon and the outermost of the inner moons. Hippocamp, formerly known as S/2004 N 1, is named after the sea creatures of the same name from Greek and Roman mythology. The orbits of Proteus and its tiny