Astronomer Steve Ruhl will examine the worlds outside our solar system — exoplanets — at the planetarium show “E is for Exoplanet” on Saturday, Sept. 8 at the Edwin E. Ritchie Observatory at Battle Point Park.

How do we see them, what do exoplanets tell us about our solar system and are there other habitable worlds out there?

The show starts at 7:30 p.m. and is free to members of the Battle Point Astronomical Association; a $2 donation suggested for nonmembers, $5 for families.

There will also be a special “Alien Invasion” Kids Show at 4 to 6 p.m. with Dr. Erica Saint Clair.

If the sky is clear, astronomers will be on hand with telescopes for public star gazing afterward.

The Battle Point Astronomical Association is a nonprofit amateur astronomy organization that operates the Ritchie Observatory and John H. Rudolph Planetarium in the Helix House at Battle Point Park.

For more information, call 206-842-9152 or visit www.bpastro.org.