What did Galileo resolve the Milky Way into?

Galileo resolved the Milky Way into a multitude of stars. Using his improved telescope in 1610, he showed that the hazy band of light was made from countless faint stars packed too closely together for the unaided eye to distinguish.

He described these observations in Sidereus Nuncius, or The Starry Messenger, published in March 1610. The telescope also revealed many previously invisible stars in constellations such as Orion and in the Pleiades. What looked like a smooth, cloudy substance was therefore an enormous collection of separate stars.

Galileo did not yet understand that the Milky Way is a galaxy, or that the Sun lies inside it. That broader interpretation developed centuries later. The observation nevertheless transformed astronomy by providing direct evidence that the night sky contained far more stars than human vision could detect.