attacking planets problem

white stars? i've never seen that before or im not sure what you mean.

a possible problem might be that your ships are out of ordnance and cant attack.

the "stars" are the mark for mines, to make your ships get into that sector you can right click and toggle "known minefield", then attack, .. better sweep those mines first

so the ship goin to attack a planet and do nothing?
are you sure the ships still ordenance?
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Every great fall begins with a single mistake, YOU just made your's........

I would second the above the fleet is either out of ordinance out of supply or avoiding the mine field which the AI has just deployed. Check that and note it as a known minefield and attack if you have sweepers if not pull back till you do as the mines will wreck your fleet otherwise

Just right click the planet and unmark it as a mine feild (remove those stars). If you look at the planet it should tell you how many mines are there. Usually mines can do at least 200 damage per mine (more for larger mines but look at the tech of the ships you are fighting to guess how advanced you think they are.

Use mine sweepers if you want, or use the Russian approach, send in your naff old ships to sweep the area for you by exploding. Or use lots of very heavily sheilded / armoured ships.