Mar 9, 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 …

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 …

Mar 10, 2026 · 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.

Mar 18, 2026 · Typically, galaxies are millions of light-years apart. Galaxies are the building blocks of our universe. Their distribution isn’t random, as one might suppose. Instead, galaxies reside along...

Feb 12, 2026 · Galaxies coverage from Scientific American, featuring news and articles about advances in the field.

Jul 13, 2022 · Here are some of the most promising theories of how galaxies form, how and why they merge, as well as the different varieties of galaxies that have been observed.

Jan 18, 2024 · Galaxies are among the largest and most beautiful objects in the night sky. These huge swirling masses are where almost every star in the Universe is born, lives and dies.

May 2, 2022 · Thus, we can define a galaxy as an astronomical object that contains millions to billions of stars from multiple generations, all of which are bound by gravity. Less than a century ago, our view …

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...