To begin with, planets form via accretion around an already existing sun. This is basic cosmology. Thus, there is no physical way that our earth could have existed before our sun.
Secondly, the Hebrew text of Gen 1 never says that our sun was 'created' on 'day' four....if that was the intent, then the creation verb 'bara' would have been employed....but, instead, a new creation verb is used 'haya' (i.e. be or exist).
Secondly, the Hebrew text of Gen 1 never says that our sun was 'created' on 'day' four....if that was the intent, then the creation verb 'bara' would have been employed....but, instead, a new creation verb is used 'haya' (i.e. be or exist).