Chinese martial arts are generally known for assigning flowery names to it's various postures, techniques and excercises. While quite often the names are similar across styles and lineages, their actual meaning is subject to the particular style, lineage or school.
From this web site (I could not find more authoritative web reference at the moment):
The seven brightest stars of the constellation are Ursa Major, the Great Bear, also called the Big Dipper.
In Eastern Asia, these stars compose the Northern Dipper. They are colloquially named "The Seven Stars of the Northern Dipper" (Chinese: 北斗七星; pinyin: běidǒu qīxīng).
Taoist believe that this star constellation is the seat of the celestial bureaucracy of the gods.
Essentially, Seven Stars is a term that has it's root in Chinese Taoist symbolism. In martial arts context, this can mean almost anything and it usually varies from lineage to lineage.
This is very well illustrated by the variety of interpretations of the term Seven stars in the answers given to this question.
In conclusion. If you want to know, what Seven stars refers to in a particular martial art, you must ask the practitioner of that art.