galaxy
Sign in to saveA galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek '''' (), meaning 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100million stars, range in size from dwarfs with less than a thousand stars to the largest galaxies known—supergiants with one hundredtrillion 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 s
AI overview
A galaxy is a vast system of stars, gas, dust, and dark matter all held together by gravity, ranging from small collections of fewer than a thousand stars to enormous supergiant galaxies containing up to one hundred trillion stars. Galaxies matter because they are the fundamental structures of the universe—our own Solar System is located within the Milky Way galaxy—and most of their mass consists of mysterious dark matter, making them key to understanding how the cosmos is organized.
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Wikidata facts
- Subclass of
- deep-sky object
- Part of
- galaxy group or cluster
- Named after
- Milky Way
- Image
- NGC 4414 (NASA-med).jpg
Show 6 more facts
- P1424
- Template:Galaxy
- P5008
- Wikipedia:Vital articles/Level/4 (2022)
- P5869
Article
43 sectionsContents
- Etymology
- Nomenclature
- Observation history
- Milky Way
- Distinction from other nebulae
- Multi-wavelength observation
- Modern research
- Types and morphology
- Ellipticals
- Type-cD galaxies
- Shell galaxy
- Spirals
- Barred spiral galaxy
- Super-luminous spiral
- Other morphologies
- Dwarfs
- Variants
- Interacting
- Starburst
- Radio galaxy
- Active galaxy
- Seyfert galaxy
- Quasar
- Other AGNs
- Luminous infrared galaxy
- Physical diameters
- Angular diameter
- Isophotal diameter
- Effective radius (half-light) and its variations
- Petrosian magnitude
- Near-infrared method
- Larger-scale structures
- Magnetic fields
- Formation and evolution
- Formation
- Evolution
- Future trends
- Gallery
- See also
- Notes
- References
- Bibliography
- External links
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek '''' (), meaning 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100million stars, range in size from dwarfs with less than a thousand stars to the largest galaxies known—supergiants with one hundredtrillion 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 centers of galaxies.
Galaxies are categorised according to their visual characteristics such as elliptical, spiral, or irregular. The Milky Way is an example of a spiral galaxy. In addition to shape, galaxies may be notable due to special properties, such as interacting with another galaxy, producing stars at an unusual rate, or having an active galactic nucleus. It is estimated that there are between 200billion () and 2trillion galaxies in the observable universe. Most galaxies are 1,000 to 100,000 parsecs in diameter (approximately 3,000 to 300,000 light years) and are separated by distances in the order of millions of parsecs (or megaparsecs). For comparison, the Milky Way has a diameter of at least 26,800 parsecs (87,400 ly). Its nearest large neighbour, the Andromeda Galaxy, is just over 750,000 parsecs (2.4 million ly) away.