purple comets in super mario galaxy

[Emo]

Can any one tell what is purple comet in super mario galaxy? I started playing this game . So want to know what is this ?
Thanks

[p A p A]

About Purple Comets

Once you beat the game, Purple Comets start orbiting space making it so when you go in the galaxy, you need to collect 100 purple coins. Collect them all and you will get another star. Now you can get all 120 (until you do the Luigi story…)

[KoYI_Bat_NAhi]

Information from gamespot

A purple comet will begin making its way throughout the galaxy, offering you the opportunity to obtain 15 more power stars. In order to do so, you'll need to track down the purple comet and enter the galaxy where it's hanging around. Doing so will launch a new minigame where you have to obtain purple coins. Lots of purple coins.

Unfortunately specific walkthroughs for these missions are a bit outside the scope of this guide, especially since these missions aren't even available until you beat the game; they vary in difficulty from the relatively easy to the maddeningly difficult.They're mostly intended to get you up to 120 stars in order to unlock Luigi's playthrough, so if you intend to pursue that goal, then feel free to give them a whirl. If you're looking for detailed guides to these missions, check gamefaqs.com; we're sure that there'll be guides for these missions relatively soon.