The “Great Nebula” in Andromeda is one of the most awe-inspiring naked-eye objects in the northern sky. From a dark site it appears as a faint smudge perhaps half the size of the full Moon, lying about 20° from the Milky Way. Though probably known since antiquity, it was first noted in the 10th century by the Persian astronomer A. al-Sufi. In his Book of the Fixed Stars, he called it the “Little Cloud” at the mouth of the “Big Fish.
”We now know that this faint ellipse is actually a great spiral galaxy — the Andromeda Galaxy, or Messier 31 — an island of hundreds of billions of stars about 2.5 million light-years away. It is the most distant object you can easily see with your naked eye. Remarkably, the light we see began its journey at the dawn of humanity... ... Take a "Swift" Tour of the Andromeda Galaxy