I love this song- it's from the new moon soundtrack.
Play the Bb/G like this:  
e|---3-------------------|
B|---3-------------------|
G|---3-------------------|
D|---3-------------------|
A|---1-------------------|
E|---1-------------------|

Intro: ~F  Bb  Bb/G  Cm  F#  F~

Verse:

Bb (x1333x@1)       Bb/GAll (20222x@1)of the astronauts
             CmChampagne (x3101x@1)in plastic cups
        F# (244322@1)        F (133211@1)     BbWaiting (x1333x@1)for the big hero to show.
Bb (x1333x@1)        Bb/GOutside (20222x@1)the door he stands
         CmHis (x3101x@1)head in his hands
        F# (244322@1)         Fand (133211@1)his heart in his throat.

Chorus:

Eb (x43121@3)        BbWhat (x1333x@1)can he tell them now?
Eb (x43121@3)    CSorry (x32010@1)I let you down
Eb (x43121@3)     F (133211@1)          BbSorry (x1333x@1)it wasn't quite true.
    Eb (x43121@3)      BbBut (x1333x@1)don't get hung up on it
Eb (x43121@3)         CJust (x32010@1)soldier on with it.
    Eb (x43121@3)           F (133211@1)          BbAnd (x1333x@1)good luck with shooting the moon.

Repeat for other verse and chorus.
Enjoy!