Ah, a happy little question! The plural possessive for "star" would be "stars'." Just add an apostrophe after the "s" when showing that multiple stars own something. Remember, there are no mistakes, just happy accidents in grammar!
The plural is stars. The plural possessive is stars'.
pLURAL ; orbits Possessive plural ; Orbits' (NB note the position of the apostrophe).
The plural possessive of "sun" is "suns'".
The plural form of the noun sky is skies.The plural possessive form is skies'.
The plural possessive form of "Zeus" is "Zeuses'."
The plural is stars. The plural possessive is stars'.
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
The plural is lads. The plural possessive is lads'.
The plural is relatives. The plural possessive is relatives'.
The plural form is suffixes. The plural possessive is suffixes'.
The plural form is stepsisters. The plural possessive is stepsisters'.
The plural form is Mexicans. The plural possessive is Mexicans'.
The plural form is echoes. The plural possessive is echoes'.
The plural form is inches. The plural possessive is inches'.
Studies' is the plural possessive of study.
The plural possessive is pals'.
Coaster's is singular possessive. The plural is coasters, the plural possessive is coasters'.