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A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. [1] The first constellations likely go back to prehistory. People used them to relate stories of their beliefs, experiences, creation, and mythology.
Star chart. A celestial map by the Dutch cartographer Frederik de Wit, 1670. A star chart is a celestial map of the night sky with astronomical objects laid out on a grid system. They are used to identify and locate constellations, stars, nebulae, galaxies, and planets. [1] They have been used for human navigation since time immemorial. [2]
Celestial cartography, [1] uranography, [2][3] astrography or star cartography[citation needed] is the aspect of astronomy and branch of cartography concerned with mapping stars, galaxies, and other astronomical objects on the celestial sphere. Measuring the position and light of charted objects requires a variety of instruments and techniques.
An aster is a cellular structure shaped like a star, consisting of a centrosome and its associated microtubules during the early stages of mitosis in an animal cell. [1]: 221 Asters do not form during mitosis in plants. Astral rays, composed of microtubules, radiate from the centrosphere and look like a cloud.
A star system consisting of exactly two stars orbiting around their common barycenter. The term is often used interchangeably with double star, though the latter can also refer to an optical double star, a type of optical illusion which is entirely distinct from true binary star systems. black hole.
Representative lifetimes of stars as a function of their masses The change in size with time of a Sun-like star Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right Chart of stellar evolution
The Northern Hemisphere page from Johann Bayer's 1661 edition of Uranometria - the first atlas to have star charts covering the entire celestial sphere Southern Hemisphere. The history of astronomy focuses on the contributions civilizations have made to further their understanding of the universe beyond earth's atmosphere. [1]
Astrocytes (from Ancient Greek ἄστρον, ástron, "star" and κύτος, kútos, "cavity", "cell"), also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical control of endothelial cells that form the blood–brain barrier, [ 1 ...