You can't make your own star system. There are three extrasolar systems that have templates for the planets in those systems. You can make planets, but the system behind making planets is that for the three extrasolar star systems that have a predefined set of planet types. However, they are unnamed and lack any detail to speak of. So you make a planet when you claim worlds in a extrasolar star system and fill out the lore sheet for the worlds you claimed to explain what the world's properties are.

As for races, assuming you are referring to intelligent aliens than yes and no. For while there is the option, me and iso will be extremely picky about the subject as it has been decided there should only be one alien species with intelligence in the RP. I should also note said alien species would have to be inferior to humans technologically, be alien-aliens and not have spaceship tech on contact. 

This is because a advanced alien race is setting breaking and the player who controlled those aliens would be as powerful as all the other players in the RP combined which isn't fair at all to everybody else.