I was just thinking about how this is done. I have looked online and I can't find a none mathematical explanation. If I am getting it right, we get the orbits by measuring the radial and tangential velocities of several stars relative to our sun. I thought the tangential velocity was unobtainable. Wouldn't you have to wait a century or two to be able to measure the tangential velocity. I am sure the answer is easy. I am just not getting it off of the explanation I was given. Can anyone explain this better to me.. or correct if I am misinformed.