To sign planet, form your non-dominant hand into a fist and keep it steady. Then form the ASL letter P sign with your dominant hand. Finally, take your 'P' hand and rotate it around your fist like a Ferris wheel rotating on its axis, up and down then up again.
This mimics a planet revolving around the Sun.
Teach your toddler the planet sign when you are watching a science show or cartoon, when you're visiting a science museum, or when you are reading their planetary picture book together.
This is a useful flash card taught best in conjunction with other science flash cards.