Want to name Pluto's two tiniest moons? Then you will need to dig deep into mythology.
Astronomers have announced a contest to name the moons discovered over the past two years.
Three Pluto moons already have names associated with Hades and the underworld. They are Charon, the ferryman of Hades; Nix for the night goddess; and the multi-headed monster Hydra.
The two unnamed moons need similar underworldly references. Right now, they go by the bland titles of P4 and P5. They're no more than 20 miles (32 kms) across.
Online voting will last two weeks. Twelve choices are available at the website Pluto Rocks. Choices include the hero who slew Hydra, Hercules; and Styx, the river to the underworld. Write-in suggestions are welcomed.
To vote, go online at www.plutorocks.com/.