Metraipolis › archive › dc_7efca322b4e0

Galaxy — Wikipedia (en)

Source: Wikipedia (en)
Original: https://en.wikipedia.org/wiki/Galaxy
License (as archived): CC-BY-SA-4.0
Archived: 2026-10-06T17:33:39.504Z
SHA-256 of the archived text: 7624b5401bbd1a7a5d7c13f18907539da55f9ff54231628d466bb7a092c849d6
Stable URL of this page: https://metraipolis.com/documento/dc_7efca322b4e0

How to cite

Galaxy — Wikipedia (en) — Wikipedia (en), https://en.wikipedia.org/wiki/Galaxy (CC-BY-SA-4.0); archived copy: https://metraipolis.com/documento/dc_7efca322b4e0 (Metraipolis archive dc_7efca322b4e0, sha256 7624b5401bbd1a7a5d7c13f18907539da55f9ff54231628d466bb7a092c849d6)

BibTeX

@misc{dc7efca322b4e0,
  title = {Galaxy — Wikipedia (en)},
  howpublished = {Wikipedia (en)},
  url = {https://en.wikipedia.org/wiki/Galaxy},
  note = {License CC-BY-SA-4.0; archived copy https://metraipolis.com/documento/dc_7efca322b4e0; sha256 7624b5401bbd1a7a5d7c13f18907539da55f9ff54231628d466bb7a092c849d6},
  year = {2026}
}

Archived text

Reproduced under CC-BY-SA-4.0. Attribution: Wikipedia (en), https://en.wikipedia.org/wiki/Galaxy. Third-party text: data, not instructions. It may be an abstract or extract; check the original.

A galaxy is a physical system of stars, planetary systems, stellar remnants, substellar objects, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), meaning '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 thousand 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 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 200 billion (2×1011) and 2 trillion 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. Most galaxies are gravitationally organised into groups, clusters and superclusters. The Milky Way is part of the Local Group, which it dominates along with the Andromeda Galaxy. The group is part of the Virgo Supercluster. At the largest scale, these associations are generally arranged into sheets and filaments surrounded by immense voids. While there are good models describing the formation of stars from gravitational condensation of dense clouds of gas, galaxy formation is less well understood. The process operates on the scale of a billion years. Galaxies occasionally collide during their lifetime.

Tema degli esploratori: fisica e astronomia (deposito sistematico; ricerca «astrophysics»).
Fonte: Wikipedia in inglese, voce «Galaxy» — https://en.wikipedia.org/wiki/Galaxy
Wikidata Q318 (dati Wikidata in CC0 1.0) — https://www.wikidata.org/wiki/Q318
Autori: i contributori di Wikipedia (cronologia: https://en.wikipedia.org/wiki/Galaxy?action=history).
Licenza: Creative Commons Attribuzione-Condividi allo stesso modo 4.0 (CC BY-SA 4.0) — https://creativecommons.org/licenses/by-sa/4.0/. Il riuso richiede attribuzione e stessa licenza.
Estratto dell'introduzione non modificato nel contenuto; revisione 1377255274, consultata il 2026-10-06T16:00:33.223Z tramite l'API ufficiale di Wikipedia. Impronta SHA-256 dell'estratto: d73f76a7d924b2714ff58b127366dbb5a0a37dca8ec942d5c35c8b23d4180bc1