Physical Characteristics

Selected physical characteristics of planets, planetary satellites, comets and asteroids are available. Links to these data are provided in each body's corresponding section below.


In addition, we provide a table representing astrodynamic constants (both defining and derived) useful in the field of solar system dynamics. Radar astrometry for selected solar system bodies is also provided on a separate page.



Selected physical parameters for the planets such as mass, mean radius, density, absolute magnitude, geometric albedo, surface gravity, and escape velocity are available in a table with references.


Planetary Satellites

Select ed physical parameters such as GM, mean radius, mean density, magnitude, and geometric albedo are available for some planetary satellites. These parameters are presented in a table with references. In addition, there is JPL lunar constants and models technical document available in PDF format.


Comets and Asteroids

Physical parameters for asteroids are not well known primarily because these bodies are so small and there are so many. The only parameter determined for nearly all asteroids is the absolute magnitude (H) which can be used to obtain a very rough estimate of an asteroid's size. However, a few asteroids have other parameters determined including rotation period, geometric albedo, colours (B-V, U-B, I-R), spectral taxonomic type, mass (GM), and bulk density.


Physical parameters for comets are even less well known than those for asteroids. Not only are comets difficult to observe because they are small, but while close enough to observe, they are typically active and thus their surface is obscured by a coma of gas and dust.


Known physical parameters for any given small body are available via our small-body database browser. Alternatively, you can generate custom tables of physical (and other) parameters for sets of small-bodies using our custom small-body database search engine.