Autonoe’s colour mystery

A light-red moon in a mostly grey family.

Published 2026-10-23

Colour is a key clue to where small moons came from.^[1]

The numbers

Pasiphae: B−V 0.74, V−R 0.38 (grey). Autonoe: B–V 0.72, V–R 0.51 (light red).^[1]

Company

Autonoe’s colour class matches Megaclite and Sinope.^[1] NASA notes Sinope is itself suspected of starting out as an independent asteroid.^[2]

Two possibilities

Autonoe may be a fragment of the Pasiphae parent body, or an independent object captured separately.^[1]

Hard to study

At magnitude 22, it can be observed only with very large telescopes, and its shape is unknown.^[1]

Numbered citations link to the sources list on the Autonoe overview page.