A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. [1][2] The word is derived from the Greek galaxias (γαλαξίας), meaning 'milky', a reference to …

Feb 6, 2026 · Galaxies consist of stars, planets, and vast clouds of gas and dust, all bound together by gravity. The largest contain trillions of stars and can be more than a million light-years across. The …

6 days ago · The existence of galaxies was not recognized until the early 20th century. Since then, however, galaxies have become one of the focal points of astronomical investigation. The notable …

Feb 5, 2026 · Discover what a galaxy is explained in simple terms, how many galaxies exist, and how the universe size shapes our view of the cosmos—packed with clear, engaging science.

Astronomy.com is for anyone who wants to learn more about astronomy and space, including planets, galaxies, asteroids, and NASA.

With more than 100 billion galaxies in the observable universe, the exciting discoveries and unanswered questions are endless. Each one is unique, from ellipticals that have quenched their star formation to …

Mar 19, 2025 · Galaxies are the grand islands of the universe, each one a vast metropolis of stars, gas, dust, dark matter, and endless possibility. From tiny dwarfs to sprawling giants, galaxies tell the story …

Explore our cosmic neighborhood in an interactive 3D map featuring the Milky Way, Andromeda, Triangulum, and dozens of nearby dwarf galaxies. Built for curious learners, stargazers, and …

Define what a galaxy is and the broad characteristics of galaxies, including galaxy types. Explain the history of observing galaxies. Recognize Hubble’s Law and its implications in astronomy. This …

Apr 17, 2019 · Galaxies are sprawling systems of dust, gas, dark matter, and anywhere from a million to a trillion stars that are held together by gravity. Nearly all large galaxies are thought to also contain...