I want to do something like Pendragon, in spaaaaace!

Just randomly create a rock, or garden world...

Lesser of two d% rolls for hundreds stacked on the bigger roll; 54 and 29 becomes 2954 meter rock, a couple of miles. Or randomly plot three d%-d% for XYZ coordinates, +25, -73, +17, a total of 79 lyr from Sol... randomly pick a star by type and find a mass and luminousity.