This week in apps features the anticipated release of Journey to the Exoplanets, which takes users on an unprecedented look at the mysterious planets outside our Solar System. Also, two Mercer Mayer storybook apps: Where Is My Frog? and Little Critter's Little Red Riding Hood, which make his books interactive. Where Is My Frog? is a hide-and-seek story and Little Red Riding Hood is the classic tale retold in Mayer's signature style. Also this week is My Little Pony: Twilight Sparkle, Teacher for a Day, which brings players to the world of Equestria, the Kingdom of Princess Celestia.

Title: Journey to the Exoplanets

Publisher: HPHLP

Release date: September 14, 2011

Price: $9.99

Background: Scientific American and Farrar, Straus and Giroux have partenered for this iPad app that explores the planets outside our Solar System.

Features: View over 100 images illustrated by Hugo-award-winning illustrator Ron Miller, an accelerometer and gyroscope allow you to get a panoramic view of the planets' surfaces, create you own planet with the Planet Builder feature, see how different types of stars change the appearance of the planets, 3D Star feature, audio tour guide, timeline, planet size chart.

Title: Where Is My Frog?

Publisher: Sterling

Release date: September 12, 2011

Price: $4.99

Background: An app in Mercer Mayer's Little Critter series, based on his lift-the-flap book. The story is a hide-and-seek tale.

Features: Choice for players to read the story themselves or be read to, word, image and counting games designed to build children's logical and perceptual skills and prepare them for reading and math, a secret game that players can unlock, every page includes a built-in counter that gives players coins for each hidden animation they uncover.

Title: Little Critter's Little Red Riding Hood

Publisher: Sterling

Release date: September 12, 2011

Price: $4.99

Background: The classic is retold in Mercer Mayer's signature style, as part of his Little Critter series.

Features: Players can choose to read the story themselves or be read to, pages feature a built-in counter that rewards players with coins when they discover hidden animations. The coins are redeemable for more activities centered around the characters. Also includes word, image and counting games to build logical and perceptual skills.

Title: My Little Pony: Twilight Sparkle, Teacher for a Day

Publisher: Ruckus

Release date: September 22, 2011

Price: $0.99

Background: Features characters Twilight Sparkle, Spike the Dragon, Applejack, Rainbow Dash, and other Ponyville friends in a story that tells players the history of Equestria, the Kingdom of Princess Celestia.

Features: Players move the adventure forward with activities like mazes and spot the difference games that teach word recognition, picture/word association and basic problem solving skills. Also includes customize-your-own-story activity, touch-driven animations and a "Meet the Poines" feature.