What did the Milky Way used to be thought of as?

The Milky Way was historically thought to be a nebula, which refers to a cloud of gas and dust in space. This concept emerged from early astronomical observations when the Milky Way appeared as a milky band of light across the night sky. Astronomers initially lacked powerful telescopes and advanced methodologies to explore the galaxy's structure, leading them to believe that the Milky Way was merely a vast accumulation of gas and dust rather than a collection of stars organized in a spiral structure.

Over time, advances in astronomy have revealed that the Milky Way is, in fact, a barred spiral galaxy that contains hundreds of billions of stars, along with planets, gas, and dust. This understanding has fundamentally shifted the perception of the Milky Way from a nebulous entity to a complex structure, highlighting the importance of technological advancement in the field of astrophysics.