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  1. Galaxy - Wikipedia

    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), literally …

  2. Galaxy | Definition, Formation, Types, Properties, & Facts | Britannica

    Nov 27, 2025 · A galaxy is any of the systems of stars and interstellar matter that make up the universe. Many such assemblages are so enormous that they contain hundreds of billions of …

  3. Galaxies - NASA Science

    May 2, 2025 · 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 …

  4. What’s a galaxy? All you need to know - EarthSky

    Mar 23, 2025 · A galaxy can contain hundreds of billions of stars and be many thousands of light-years across. Our own galaxy, the Milky Way, is around 100,000 light-years in diameter.

  5. What is a Galaxy? - sciencenewstoday.org

    Mar 19, 2025 · The Basics: What Is a Galaxy, Really? At its core, a galaxy is a massive, gravitationally bound system consisting of stars, stellar remnants, interstellar gas, dust, and …

  6. Galaxies—facts and information | National Geographic

    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...

  7. What is a galaxy? - BBC Sky at Night Magazine

    Jan 18, 2024 · A galaxy is a concentration of millions or billions of stars, gas clouds and pockets of dust, all bound by gravity and swathed in a cocoon of mysterious dark matter.

  8. How Galaxies Work | HowStuffWorks

    Nov 8, 2023 · A galaxy is a large system of stars, gas (mostly hydrogen), dust and dark matter that orbits a common center and is bound together by gravity — you can think of them as …

  9. What Is a Galaxy? | NASA Space Place – NASA Science for Kids

    Sep 25, 2025 · What Is a Galaxy? The Short Answer: A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems, all held together by gravity. We live on a planet …

  10. NASA's Chandra telescope uses 'X-arithmetic' to reveal how black …

    2 days ago · Stunning new images from NASA's Chandra X-ray Observatory reveal galaxy clusters in vivid colors, showing how supermassive black holes heat and shape surrounding …