A simple guide to finding every secret star in Super Mario Galaxies. The stars are listed by galaxy and level as well as a description of the turnoff and screenshots. Rows highlighted in green are the green stars. Also, I mainly focussed on the turnoff towards each star, because after that it is usually a pretty straightforward path.
Luigi Stars*
| Galaxy | Level | Description
| Screenshots |
Good Egg Galaxy (Terrace) | Dino Piranha | Walk behind the house at the beginning of the level. From there walk to the reverse side of the planet and go down the orange tube to get to Luigi | |
| Honeyhive Galaxy (Terrace) | Bee Mario Takes Flight
| Go to where the boulders are coming down and grab the bee suit. From there fly on top of the branch the trapeze is hanging from nearby. Then fly up to where the piranha plans are. You'll have a clear-cut path to Luigi from there | |
Battlerock Galaxy (Fountain) | Battlerock Barrage | When you reach the normal star for this section, go to the bottom of the planet. Incased in glass is Luigi. Lead a bullet bill there to get Luigi and his star | |
Fountain
| Galaxy | Level | Description
| Screenshots |
| Space Junk Galaxy | Tarantox's Tangled Web | Collect 50 star bits for the hungry luma, which will send you to a planet shaped like yoshi's head. Kill all the goombas on this planet for the star. | |
Battlerock Galaxy
| Breaking into the Battlerock
| Collect all the star bits at the beginning. You should have plenty to feed the hungry luma, which leads you towards the garbage dump. throw the bombs on the coin slots on the ground to clear the garbage | |
Kitchen
| Galaxy | Level | Description
| Screenshots |
| Buoy Base Galaxy | The Floating Fortress | This one is easy. Swim to the bottom of the water to find a pipe encased in glass. Have a bullet bill chase you into this, then take the pipe to a green star | |
Beach Bowl Galaxy
| The Secret Undersea Cavern
| Find the big waterfall where the penguin says "press z to slow down while shell swimming". go around the waterfall and you'll find a chest. Break open this chest to find a launch pad which will take you on the path to the star. Use the Ice Man suit to wall jump on the waterfalls |  |
| Ghostly Galaxy | A Very Spooky Sprint | Take the launch pad from the starting point, then break the glittery block to find the path to the star. From here it’s a fun game of stay in the spotlight to the next star | |
Bedroom
| Galaxy | Level | Description
| Screenshot
|
| Freezeflame | The Frozen Peak of Baron Brrr | When you first get the ice Mario suit, use it to jump on the fountains in front of you. Once you reach the top you are a trek of snowman killing and ice bat avoiding away from the star |
|
Gusty Garden Galaxy
| Gusty Garden's Gravity Scramble
| Gusty Garden's Gravity Scramble - Collect all the large coins on you're way to the island with the golden chomper. This will get you an invincibility star, which you can use on the chomper. Kill the chomper to collect you're star |
|
| Dusty Dune Galaxy | Blasting Through the Sand | On the bottom of the second planet you land on you'll find a hungry luma. Feed the luma to get to the next planet, where you'll collect 5 silver stars to get a green star | |
| Dusty Dune Galaxy | Sun baked Sand Castle | Go to the third planet (the one after the annoying sand castle). You'll notice the sand goes up and down, which reveals a stump. Butt smash the stump, then collect the notes. This will take you to another (sigh) sand castle that goes up and down. Get a bullet bill to follow you into the glass to collect the star | |
Engine Room
| Galaxy | Level | Description
| Screenshots |
Sea Slide Galaxy | The Silver Stars of Sea Slide | Grab the Bee suit and feed the hungry luma by the cannon. Shoot yourself with the cannon onto the new planet, and grab all the notes to get your star | |
| Gold Leaf Galaxy | Cataquack to the Skies
| Get launched by the first cataquak to the big tree. As you walk around it you will notice a bubble get shot into the air. Jump into it, hit the bell on the tree, and collect the notes to get your star |
|
Toy Time Galaxy | Mario Meets Mario | This one is pretty straightforward. When you launch from the train to the giant screw, just launch from the star that is already there, instead of collecting the shards. This will take you to a planet of thwomps and a straightforward path to the star | |
Garden
| Galaxy | Level | Description
| Screenshots |
Dreadnought Galaxy | Revenge of the Topman Tribe | As soon as you enter the galaxy, just walk to the other side of the first planet you land on. A tube will take you to a minigame of blowing up garbage. Place the bombs on the coins to take it all out | |
| Melty Molten Galaxy | The Sinking Lava Spire
| Collect 80 star bits for the hungry luma you will find after the volcano. If need be, die repeatedly at the start of the level after collecting a few at a time for an easy go at this | |
Deep Dark Galaxy | The Underground Ghost Ship | Underwater you will find a large anchor with what appear to be mines around it. hit it with a turtle shell and it will open up a launch star to take you towards your next star | |
Notes
*Luigi stars are extra stars Luigi helps you find after you rescue him from the mansion. You can ONLY find these stars after receiving a letter from him, then going to that location.
As a side note, if there are any items I'm not clear on, or anything you feel should be added, feel free to mention them in the forums. I'll be happy to update this guide with anything that might be more helpful. Thanks!