Battle Stars are located by unlocking the Season 9 Loading Screens within the Utopia Event. Loading Screens are unlocked by completing the Weekly Challenges which are part of the Battle Pass.
The Battle Stars can only be discovered after you have completed the Weekly Challenges and unlocked the applicable Loading Screen. If you go to their location without unlocking the Loading Screen first, then the Battle Star will not appear.
How to find the Week 1 Hidden Battle Star
The Week 1 Battle Star location can be unlocked by completing all challenges in any week of the Battle Pass Weekly Challenges. This will reward you with Loading Screen #1 which has the coordinates for the Battle Star on it.
The location of the Week 1 Battle Star can be seen on the mini gun, which reads I5, I6, J5, J6. This will lead you to the location circled in red on the map below, which is located between the racing track and Lonely Lodge on the right hand side of the map.
The Battle Star is in the grass right next to a hill. You should see a transforming truck in front of you if you’re facing the race track.
How to find the Week 2 Hidden Fortbyte
The Week 2 Hidden Fortbyte (Fortbyte #13) can be found at a location which is hidden within Loading Screen #2, which can be seen below.
This will lead you to bottom right corner of the map, which is circled in blue.
Once you get there, you will see three dinosaurs and a small house close to the road. Go behind the small house where you will find a port-a-potty. Approach the portable restroom and you will see the Week 2 Hidden Fortbyte.
How to find the Week 3 Hidden Battle Star
The Week 3 Hidden Battle Star can only be found once players have completed all of the Weekly Challenges from Weeks 1-3. If you have already done that, then keep reading to figure out how to find the Week 3 Hidden Battle Star!
The location of the Week 3 Battle Star can be found in loading screen #3, which can be seen above. As you can see, there a a blue arrow on the concrete block and to the left arrow is a pile of cars with a shiny object on top.
This should lead you to Junk Junction, where you can find the exact same pile of cars (see image below). Build up to the top of the cars and you’ll find the Week 3 Hidden Battle Star waiting for you!
There are plenty of materials around junk junction to give you the mats needed to build your way up to the battle star.