Celestia
FreeLeave the ground and fly to any planet, star or galaxy
Open-source real-time 3D space simulation. Select an object, press G and you fly there; orbit planets, moons and spacecraft, or keep going out of the Milky Way. Time can run faster, slower or backwards, bodies follow real orbital data, and community add-ons supply extra models and textures.
Why we picked it
GPL-2.0, 2,367 stars. First released in 2001 and still receiving commits.
It is often mentioned alongside Stellarium, but the viewpoint is the opposite. Stellarium looks up from the ground; Celestia puts you in space. Select Saturn, press G to fly there, right-drag to orbit the rings, then press H to return to the Sun. You can pull back light years away and watch the solar system shrink to a point.
It is good for showing children the scale of the solar system, far more directly than a textbook illustration, and for anyone who wants to see a probe's trajectory or what a particular moon looks like. The built-in Tour Guide lists interesting destinations and is a reasonable first stop.
To be clear about:
- The desktop stable release is still 1.6.4 (November 2023). 1.7 has been in development for a long time, with nightly Windows builds. The "new Celestia" on mobile and the Microsoft Store is based on 1.7.
- The mobile and Mac App Store builds have a subscription. Versions from the App Store and Google Play offer Celestia PLUS (subscription or one-time lifetime purchase), which adds extras such as custom fonts, add-on categories and add-on search. The space simulation itself is free. Android users can install from F-Droid instead.
- The App Store version collects crash data not linked to identity. The desktop version works fully offline.