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The Milky Way is the galaxy that includes the Solar System, with a diameter of 26.8 ± 1.1 kiloparsecs (87,400 ± 3,600 light-years ). It is a barred spiral galaxy with a supermassive black hole at its center and many satellite galaxies.
In astronomy, galactocentrism is the theory that the Milky Way Galaxy, home of Earth ' s Solar System, is at or near the center of the Universe. [1] [2]Thomas Wright and Immanuel Kant first speculated that fuzzy patches of light called nebulae were actually distant "island universes" consisting of many stellar systems. [3]
Learn about the Sun and the objects that orbit it, including the eight planets, the nine dwarf planets, and the small bodies such as asteroids, comets, and moons. Explore the formation, evolution, and features of the Solar System and its place in the Milky Way galaxy.
5th century BC — Democritus proposes that the bright band in the night sky known as the Milky Way might consist of stars. 4th century BC — Aristotle believes the Milky Way to be caused by "the ignition of the fiery exhalation of some stars which were large, numerous and close together" and that the "ignition takes place in the upper part of the atmosphere, in the region of the world which ...
Galactic astronomy is the study of the Milky Way galaxy and all its contents, in contrast to extragalactic astronomy. Learn about the subcategories, topics, and methods of galactic astronomy, as well as its history and applications.
The galactic year, also known as a cosmic year, is the duration of time required for the Sun to orbit once around the center of the Milky Way Galaxy. Learn about the origin, orientation, and events of the galactic year, and see a timeline of the universe and Earth's history in galactic years.
This web page lists the largest cosmic structures in the observable universe, such as superclusters, galaxy filaments and quasar groups, based on their longest dimension in light-years. It also explains the challenges and uncertainties of measuring and defining these structures, and provides references and links to related topics.
Modified Newtonian dynamics (MOND) is a theory that modifies Newton's law of gravity to explain galaxy rotation curves without dark matter. It was proposed by Mordehai Milgrom in 1983 and has some successes and failures in explaining various astronomical observations.