Welcome to Celestia

... The free space simulation that lets you explore our universe in three dimensions. Celestia runs on Windows, Linux, and Mac OS X.

Unlike most planetarium software, Celestia doesn't confine you to the surface of the Earth. You can travel throughout the solar system, to any of over 100,000 stars, or even beyond the galaxy.

All movement in Celestia is seamless; the exponential zoom feature lets you explore space across a huge range of scales, from galaxy clusters down to spacecraft only a few meters across. A 'point-and-goto' interface makes it simple to navigate through the universe to the object you want to visit.

Celestia is expandable. Celestia comes with a large catalog of stars, galaxies, planets, moons, asteroids, comets, and spacecraft. If that's not enough, you can download dozens of easy to install add-ons with more objects.

Features:

* Added light from secondary sources (i.e. "planetshine")
* Implemented depth sorting for markers so that they are correctly occluded
by foreground objects.
* Implemented code package rendering globular clusters
* Implemented new cel URL version with observer position and orientation stored
in frame coordinates (for forward compatibility)
* Added a long term (+-5000 centuries) precession model for Earth based on
work by Jan Vondrak
* Improved celestial coordinate grids:
- Added new grid types: ecliptic, horizontal, and galactic
- Made grid resolution adapt to the field of view
- Positioned coordinate labels at edges of field of view
* Added animated selection indicator
- Switches to direction pointer when the selection is off screen
- Changes color when the selected object is occluded
* Implemented more flexible system for reference marks and added new
reference marks:
- Planetographic grid
- Terminator
- VisibleRegion
* Enabled display of the phase angle for the currently selected object
* Improved eclipse rendering: correctly calculate depth and umbra radius
for eclipses.
* Improved star handling code so that stars can be placed more than 16k light
years from Earth.
* Switched to using sd prefix for hot subdwarfs per arXiv:0805.2567v1
* Added symbols for locations