There are several astronomy songs on the album: What is a Shooting Star?, How Many Planets?, Why Does the Sun Shine?, Why Does the Sun Really Shine? ROY G. BIV
How Many Planets? is the only song I know of that mentions Eris. Are there others?
Thanks to CaptainCaustic for letting me know about this.
You can read a review of the project here from Wired and can buy it on iTunes and