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 'milky', a reference to the Milky Way galaxy that contains the Solar System.

Aug 15, 2025 · What is a galaxy? 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 stars. Galaxies usually exist in clusters, some of which measure hundreds of millions of light-years across.

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-years across. The smallest can contain a few thousand stars and span just a few hundred light-years.

May 9, 2025 · In modern times, though, we use “galaxy” more generically to refer to any large system of stars, gas, dust and dark matter, all held together by their mutual gravity.

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 dark matter.

Nov 8, 2023 · So much about galaxies remains a mystery. We know what they're made of and that we live in one (the Milky Way), but how many galaxies are in the universe?

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.

May 29, 2018 · Galaxy A galaxy is a large collection of stars similar to the Milky Way galaxy in which our solar system is located. Astronomers classify galaxies according to their shape as either spiral , elliptical, or irregular. Spiral galaxies are further subdivided into normal and barred spirals. Elliptical galaxies can be either giant or dwarf ellipticals, depending on their size. …

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 …

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...