The co-star is an astrology social app that allows you to learn knowledge about astrology and also socialize with other people. Under Robert Cialdini’s six principles, it provides social proof, for people could be influenced if their friends are using it and invite them to pair up to see how compatible you are. It also provides a commitment to consistency, for it has everyday updates for you to see. Due to the common beliefs in the close connection between astrology and individual personalities, people like this app. Also, it has some astronomical scientific data provided by NASA and also astrology history supports, which provides authority to the app.