The basic structural unit of the universe appears to be the galaxy. A Galaxy is a collection of billions of stars an various amounts of gas and dust held together by gravity.

3 TYPES OF GALAXIES SPIRAL ELLIPTICAL IRREGULAR THERE ARE 100,000,000,000 GALAXIES THERE ARE 100,000,000,000 STARS IN EACH GALAXY 3 TYPES OF GALAXIES THAT’S 10,000,000,000,000,000,000,000 STARS IN THE WHOLE UNIVERSE The sun is one.

Spiral Galaxy (The Andromeda)

Blue color indicates very HOT stars Spiral Spiral Blue color indicates very HOT stars

Edge-on view of the Milk Way Galaxy

Barred Spiral

Elliptical M87 Much more massive than Milky Way. Mostly cool stars - gives it a yellowish color Elliptical

Elliptical NGC 5078 The smaller galaxy has been distorted into an 'S' shape by the interaction (gravity). Encounters between galaxies such as this are common, can lead to them merging into a single entity. 80 million light years away Elliptical The dust lane is warped and broadened, probably by interaction with the faint companion galaxy IC 879, which is itself distorted into an 'S' shape by the interaction. 80 million light years away

Irregular NGC 1313 Scattered patches of star formation –no real shape. 15 million light years away Irregular 15 million light years away

Colliding Galaxies Colliding Galaxies

Cartwheel Galaxy 500 million light years away. The Cartwheel itself was a galaxy about as big as the Milky Way probably with much the same spiral structure. However, one of the small companion galaxies has recently passed through its center. Cartwheel Galaxy 500 million light years away. The Cartwheel itself was a galaxy about as big as the Milky Way probably with much the same spiral structure. However, one of the small companion galaxies has recently passed through its center.

Galaxy cluster 3 Billion Light years away! 3 Billion Light years away!

MORE GALAXIES MORE GALAXIES

Approximately 100,000 light years across Milky Way Milky Way galaxy Approximately 100,000 light years across