For ten points, name this Local Group galaxy that contains the Solar System.
Harlow Shapley argued that this entity was the entire Universe at a 1920 "Great Debate," shortly before Edwin Hubble proved him wrong. Hubble then estimated the distance from this entity to its nearest neighbor, which was wrongly listed as a spiral nebula in the (*) Messier catalog. The Orion Arm is part of this system, which is on a collision course with Andromeda. For ten points, name this Local Group galaxy that contains the Solar System.
Harlow Shapley argued that this entity was the entire Universe at a 1920 "Great Debate," shortly before Edwin Hubble proved him wrong.
Milky Way (prompt on "the galaxy" before "galaxy" is read; do not accept or prompt on the solar system)