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c. 560 BCE – Anaximander is arguably the first to conceive a mechanical model of the world, although highly inaccurate: a cylindrical Earth [11] floats freely in space surrounded by three concentric wheels turning at different distances: the closest for the stars and planets, the second for the Moon and the farthest for the Sun, all conceived ...
The first generation of stars, known as Population III stars, formed within a few hundred million years after the Big Bang. [49] These stars were the first source of visible light in the universe after recombination. Structures may have begun to emerge from around 150 million years, and early galaxies emerged from around 180 to 700 million years.
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 ...
The Hubble Space Telescope, the first large optical telescope in orbit, is launched using the Space Shuttle, but astronomers soon discovered that it is crippled by a problem with its mirror. A complex repair mission in 1993 allows the telescope to start producing spectacular images of distant stars, nebulae, and galaxies.
c. 840 — Al-Farghani's Compendium of the Science of the Stars; c. 900 — Al-Battani's Az-Zij as-Sabi; 964 — Abd al-Rahman al-Sufi (Azophi)'s star catalog Book of the Fixed Stars; 1031 — Al-Biruni's al-Qanun al-Mas'udi, making first use of a planisphere projection, and discussing the use of the astrolabe and the armillary sphere.
1929 — George Gamow proposes hydrogen fusion as the energy source for stars; 1938 — Hans Bethe and Carl von Weizsäcker detail the proton–proton chain and CNO cycle in stars; 1939 — Rupert Wildt realizes the importance of the negative hydrogen ion for stellar opacity; 1952 — Walter Baade distinguishes between Cepheid I and Cepheid II ...
A graphical view of the Cosmic Calendar, featuring the months of the year, days of December, the final minute, and the final second. The Cosmic Calendar is a method to visualize the chronology of the universe, scaling its currently understood age of 13.8 billion years to a single year in order to help intuit it for pedagogical purposes in science education or popular science.
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