Stellarium: Point Your Phone at Any Star and Learn What It Is

Stellarium is a free, open-source planetarium application that turns your smartphone into a window on the universe. When you hold your phone up toward the night sky, Stellarium uses your GPS location, the device's compass, and the current time to show you an accurate map of exactly what is above you. Stars, planets, constellations, nebulae, and satellites are all labeled and positioned correctly for your location at that exact moment.

The app is often described as a "sky map," and that is the most accurate way to think about it. Unlike a static star chart from a book, Stellarium moves in real time as you tilt and rotate your phone. Pan left, and the display shows what is to your west. Tilt the phone toward the ground, and you can see what the sky looks like on the other side of the Earth.

Stellarium is available as a free web app at stellarium-web.org and as a more feature-rich mobile app. The mobile version is called Stellarium Plus on iPhone and Android, with a small one-time purchase for the full feature set — but the free web version is excellent for most casual stargazers.

Stellarium is developed by a community of astronomers and software developers who have maintained it since 2001. It is used by professional planetariums around the world as well as by amateur astronomers who want a reliable and accurate sky guide. The database includes more than 600,000 stars, all of the major planets, hundreds of deep-sky objects (distant galaxies and nebulae), and real-time satellite tracking.