Portal:Astronomy

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The Astronomy Portal

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A man sitting on a chair mounted to a moving platform, staring through a large telescope.

Astronomy is a natural science that is the study of celestial objects (such as moons, planets, stars, nebulae, and galaxies), the physics, chemistry, and evolution of such objects, and phenomena that originate outside the atmosphere of Earth, including supernovae explosions, gamma ray bursts, and cosmic background radiation.

Astronomy is one of the oldest sciences. Prehistoric cultures have left astronomical artifacts such as the Egyptian monuments and Nubian monuments, and early civilizations such as the Babylonians, Greeks, Chinese, Indians, Iranians and Maya performed methodical observations of the night sky. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars, but professional astronomy is nowadays often considered to be synonymous with astrophysics. Template:/box-footer

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This illustration compares the rapidly rotating Vega (left) to the smaller Sun (right).
Vega (α Lyr / α Lyrae / Alpha Lyrae) is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus. It is a relatively nearby star at only 25 light-years from Earth, and, together with Arcturus and Sirius, one of the most luminous stars in the Sun's neighborhood. It is 3.845 times hotter than the Sun.

Vega has been extensively studied by astronomers, leading it to be termed "arguably the next most important star in the sky after the Sun." Historically, Vega served as the northern pole star around 12,000 BCE and will do so again at 13,727 CE when the declination will be +86°14'. Vega was the first star other than the Sun, to have its photograph taken and the first to have its spectrum photographed. It was also one of the first stars to have its distance estimated through parallax measurements. Vega has served as the baseline for calibrating the photometric brightness scale, and was one of the stars used to define the mean values for the UBV photometric system.

In terms of years, Vega is only about a tenth the age of the Sun, but it is evolving so quickly that it has already approached the midpoint of its life expectancy, as has the Sun. It has an unusually low abundance of the elements with a higher atomic number than that of helium. Vega is also a suspected variable star that may vary slightly in magnitude in a periodic manner. It is rotating rapidly with a velocity of 274 km/s at the equator. This is causing the equator to bulge outward because of centrifugal effects, and, as a result, there is a variation of temperature across the star's photosphere that reaches a maximum at the poles. From Earth, Vega is being observed from the direction of one of these poles.

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Template:/box-header Astronomy : Archaeoastronomy - Astrophysics - Calendars - Catalogues - Celestial coordinate system - Celestial mechanics - Cosmology - Images - Large-scale structure of the cosmos - Observatories - Planetary science - Telescopes - Universe

Biographies : Astronomers - Other people - Amateur Astronomers

Astronomical objects : Lists - Galaxies - Nebulae - Planets - Stars

Spaceflight : Human spaceflight - Satellites - SETI - Spacecraft Template:/box-footer

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WikiProject Astronomy WikiProject Solar System

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WikiProject Cosmology WikiProject Spaceflight

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Star Spaceflight Moon
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Space Solar System Mars
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X-ray astronomy Cosmology Jupiter

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M82 HST ACS 2006-14-a-large web.jpg
Credit: NASA / ESA / Hubble Heritage Team (STScI/AURA)

Messier 82, also known as NGC 3034, Cigar Galaxy, and M82, is the prototype starburst galaxy about 12 million light-years away in the constellation Ursa Major. The starburst galaxy is five times more luminous than the whole Milky Way, and one hundred times more luminous than our galaxy's center. This mosaic image, taken by the Hubble Telescope, is the sharpest wide-angle view ever obtained of Messier 82.

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Template:/box-header All times UT unless otherwise specified. Portal:Astronomy/Events/September 2019

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