Galaxy

A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek galaxias, literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a hundred million stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies. Galaxies are categorized according to their visual morphology as elliptical, spiral, or irregular. Many are thought to have supermassive black holes at their centers. The Milky Way's central black hole, known as Sagittarius A, has a mass four million times greater than the Sun.

Read more in the app

Galaxy Caught Turning on Lights at Cosmic Dawn, Stunning Astronomers

Astronomers Find Giant Dinosaur of a Galaxy

Webb telescope sees galaxy in mysteriously clearing fog of early universe

NASA’s Webb Sees Galaxy Mysteriously Clearing Fog of Early Universe

'Space tornadoes' discovered at the center of our galaxy

A 'Star Grinder' Swarm of Black Holes Could Lurk in Our Galaxy's Dusty Core

M51 - The Whirlpool galaxy

Oxygen Found in a Galaxy Just 300 Million Years After the Big Bang

Stellar nursery sparkles at the edge of our galaxy in gorgeous Hubble Telescope image

The 10 best space RPGs of all time: Explore the galaxy in these stellar role-playing games

Hubble Focuses on Star-Studded Region in Neighbor Galaxy

A U-Michigan led team of researchers has discovered Andromeda XXXV, the smallest and faintest known galaxy orbiting Andromeda, the Milky Way's major galactic neighbor. The find challenges past theories on evolution and star formation in satellite galaxies.

Mysterious phenomenon at center of galaxy could reveal new kind of dark matter - EurekAlert

Mysterious phenomenon at center of galaxy could reveal new kind of dark matter

Mysterious phenomenon at center of galaxy could reveal new kind of dark matter

Hidden monster black hole in the galaxy next door fired stars at us like million mph cosmic bullets

Black Hole at The Center of Our Galaxy Seen 'Bubbling' With Activity

Astronomers spot flares of light near the black hole at the center of our galaxy

Webb Space Telescope Tracks Fireworks Around Our Galaxy’s Black Hole

NASA’s Webb Captured Something Strange Happening at the Heart of Our Galaxy