Where can I find data on planetary positions and velocities?
March 17, 2008 1:33 PM   Subscribe

I'm working on a computer simulation of the solar system, but I need data on the positions and velocities on planets and their moons. (more inside)

For a class project, I'm working on a 3D simulation of the solar system. However, I need to get good data on the positions and velocities of planets and their moons. I've managed to find a lot of sites with information about planetary positions as viewed from earth, but the way I'm constructing it, I need to be able to locate them by x, y, and z coordinates with the Sun at the origin.

Any ideas where I might find any good data? Also, anywhere with an analytical solution to the position of a planet with respect to the Sun would be helpful as well.

posted by deansfurniture5 to Science & Nature (5 answers total) 5 users marked this as a favorite
posted by Guy_Inamonkeysuit at 1:40 PM on March 17, 2008

Best answer: You might also check JPL's ephemeris[?] generator, available here (or more generally here)--this is the most detailed data, the sort used to make trajectories for interplanetary spacecraft, and accounts for gravitational interactions between the smaller bodies. They offer a number of types of data through the main SSD page as well--they can give you orbital elements if you just want to do a simple Keplerian model.
posted by Upton O'Good at 2:12 PM on March 17, 2008

Stellarium is open source. Would it be cheating to use its data? Come to think of it, it may assume an earth-centric coordinate system. Howzabout Celestia?
posted by mumkin at 2:15 PM on March 17, 2008

If you have vectors for the sun and for the planets relative to earth, just subtract the position and velocity vector for the sun from the vectors for each planet to move to the sun's frame.

There is no analytical solution to the problem of n bodies interacting gravitationally... (not to mention effects from general relativity, solar wind interacting with planetary magnetospheres, asteroid belts and other nastiness). If you neglect everything besides gravitational interaction with the sun you get Keplerian orbits-check you favorite classical mechanics text for solutions.
posted by njgo at 3:49 PM on March 17, 2008

Response by poster: Thanks everyone for your help, I'll definitely be checking out the sites you suggested.

@njgo: I was looking for some way to predict the position of a planet x amount of time in the future so I can see how good my simulation is. I'm sure the basic orbits will be fine, which I found info on between posting the question and checking back. Thanks!
posted by deansfurniture5 at 4:23 PM on March 17, 2008

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