Celestia is a free space simulation that lets you explore our universe in three dimensions. The program is based on the Hipparcos Catalogue and allows users to travel through an extensive universe, modeled after reality, at any speed, in any direction and at any time in history. Celestia displays and interacts with objects ranging in scale from artificial satellites to entire galaxies, from perspectives which would not be possible from a classic planetarium or other ground based display.
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.
— Celestia displays the Hipparcos Catalogue (HIP) of almost 120 000 stars.
— Celestia uses the very accurate VSOP87 theory of planetary orbits. Display the orbital paths of planets (including extrasolar planets), dwarf planets, moons, asteroids, comets, artificial satellites, and spacecraft.
— The user can vary the number of stars that are visible on the screen and have them drawn in different styles.
— Celestia users can travel through the Celestia universe using simple keyboard controls, at any speed from 0.001m/s to millions of light years/s.
— The time simulated by Celestia can be set at any point in the future or past, although planetary orbits are only accurate within a few thousand years of the present day, and date arithmetic overflows at the year 5874774.
— The names and positions of multitudes of objects in space can be displayed, from galaxies, star clusters, nebula, constellations and stars to planets, moons, asteroids, comets and artificial satellites.
— Celestia displays such features as detailed atmospheres on planets and moons, planet shine on orbiting satellites, sunsets and sunrises, moving clouds, planetary rings, eclipse and ring shadows, constellation lines, borders and illustrations, night-side lights, detailed surface textures, specular reflections off water and ice, nebula gases and star flares.
— Information about the objects that Celestia draws can also be displayed: the radius, the distance, length of the sidereal day and average temperature of the planets are shown and the distance, luminosity relative to the sun, spectral class, surface temperature and radius of stars are indicated.
— The user can change Celestia’s field of view from as wide as 120 degrees to a highly magnifying 3.4 seconds of arc.
— Graphic screen-shots and movies can be captured in classic or HD resolutions (up to 1920×1080).
— Celestia’s support for game pads and joysticks is relatively limited, employing many keyboard shortcuts instead.
— Celestia can be extended with new objects and there are hundreds of third-party, user-created add-ons available for installation, both fictional and realistic.