Asteroids are obstacles that act as hazards that can disrupt and damage ships.
While a ship executes a maneuver, if it moves through or overlaps an asteroid it rolls one attack die. On a 
result, the ship suffers one damage; on a 
result, it suffers one damage. Then the ship skips its Perform Action step this round. The Adaptive Ailerons maneuver of the TIE/sk Striker and the TIE Reaper is the exception to this, as FFG has explicitly stated that these ships do not skip their Perform Action step after they overlap a ship or asteroid.
While a ship is moving, but not executing a maneuver, if it moves through or overlaps an asteroid, it executes its move as normal but suffers the same effect as if it executed a maneuver through the asteroid.
While a ship is at range 0 of an asteroid it cannot perform attacks.
While a ship performs an attack, if the attack is obstructed by an asteroid, the defender rolls one additional defense die.
Huge Ship Effects
After a huge ship overlaps an obstacle, the obstacle is removed from the play area. Then the huge ship suffers an effect according to the type of obstacle it overlapped.
For Asteroids (and Debris Clouds), the huge ship suffers one damage and gains one stress token.
Then the huge ship continues to resolve its activation. It does not skip its Perform Action step.