In Starbound, coordinates only go up to 999999999, or 9 digits, but using the arrow keys, you can go beyond said limit. so, I decided to embark on a journey off the grid to see what was beyond the coordinate boundary... after five minutes I got bored. it still begs the question though... how far out do I have to travel to reach the end of the galaxy?
If I had to guess, coordinates are stored as signed long int, so between -2 147 483 648 and 2 147 483 647.