asterism

noun3

1. •
   An unofficial constellation (small group of stars that forms a visible pattern).

   • The Big Dipper, Summer Triangle, and Orion's Belt are asterisms.
2. •
   A rarely used typographical symbol of three asterisks arranged in a triangle, ⁂, used to call attention to a passage or to separate subchapters in a book. Distinct from a dinkus which also uses asterisks to separate.
3. •
   A star-shaped figure exhibited by some crystals by reflected light (as in a star sapphire) or by transmitted light (as in some mica).