Super Mario Galaxy 2/Green Stars/World 1

World 1 had originally 17 golden ones, so it now have another 17 green ones.

Note that, while the green stars would be in their original level, its advised to pick in the Galaxy Star selection screen the empty green stars so the game will send you exactly to the level they are in, so you won't have to search level by level yourself. And by thus the lists will follow.

Sky Station Galaxy
Green Star 1

The Green Star here will be located at Yoshi's house roof near the green pipe. There's two ways to gain it - short way and long way. The short way is simply locate Mario beneath the green star, make an backward jump and add a spin. The longest is going through the green pipe, break the crystal on the hill, and then drop from the roof on the Green Star.

Green Star 2

This Green Star is located on the 2nd platform. Do the level as usual (you may collect more 1-Ups on the way) until reaching the peak of the tower. There, behind the fence you will see the Green Star shine. Drop behind the tower to get it. You may as well moving the camera to get a better look.

Green Star 3

Go through the first platform. In the second one, move to the second elevator (the one that's going down) and wait 'till you get to the level where the blue disc is, make backward jump to reach it. Hovering upon it one the side, you will find the Green Star. To reach it, make either wall jump to its side and add a spin, or a backward jump with a spin.

Yoshi Star Galaxy
Green Star 1

This green star will be shown on the level cutscene, high above the hill to the northwest of the first area. Eliminate the Magikoopa to release Yoshi, and take him above the hill (it's also the hill where the Comet Shard is). A regular floating jump won't reach it, to actually reach it, make Yoshi a float jump, and once in the air press Z+A to make Mario jump from Yoshi, and he will reach the star.

Green Star 2

Like Green Star 1, this one also can be seen in the open cutscene. But only if you look at the right side of the screen. Upon entering the level also it can be seen when you go little forward and look on the right side - it is located on the mouth cliff of the volcano. To get there, do the level as usual to take Yoshi. Upon encountering the huge fruit, got to the right side of it and you should see the star. Make Yoshi it's floating jump to get to that cliff (be careful not to slip), and take the star.

Green Star 3

This time, the green star will be on the last level platform. So just make your way through this level until you get to where the star usual is, but instead landing on the golden star land, continue the flower jumping to the left side. Once there you will see the green star hovering up in the air. To reach it, make Yoshi float higher from where the flower get you, but that won't be enough either, so press A+Z on the highest float, and Mario will jump from Yoshi toward the green star.

Spin-Dog
Green Star 1

Go through the first platform to the second one. There, the Green Star will hang above the fence on the middle of the planet. To reach the top of the fence itself, locate Mario close to the fence and make a backward jump, if Mario doesn't hang on it, add a spin. Once on the fence, locate Mario beneath the star to it's left or right, face Mario to the other side and make a backward jump and a spin to collect the star.

Green Star 2

In the third platform, proceed to where Luma is making a Star Launcher for you, and there, above the row of transforming platforms, the Green Star will hover very high in the air. To reach it there's need to make a perfect triple jump without falling when the platforms disappear. Make Mario start the triple jump before the first row of the transforming platform to make sure that Mario will be jumping toward the star. Once made the third jump, add a spin, and Mario will collect it. It's advised to eliminate the Flying Goomba before doing it.

Green Star 3

Go through the levels until you enter the green pipe to the 2D cave. In the second room the star will hover close to the wall. To reach it you must make Mario ditch the digger by getting hurt by the digger enemy. Now, locate Mario with the back to the wall facing the star, make a backward jump and make a wall jump with a spin to get the star.