Ahu Akivi at night with the milky way. Polynesians used the stars to navigate and orient themselves at sea.
The 7 Moai (5 pictured) represent the 7 explorers sent to scout the island before the arrival of Hotu Matu'a. Constructed around 1450 ce (Complete Guide to Easter Island, Shawn McLaughlin p 135)
There is a Polynesain legend that agrees with the Rapa Nui one