Portal:Astronomy
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Portal:Astronomy
The Astronomy Portal

Introduction

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

Astronomy (from Greek: ?) is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates outside Earth's atmosphere. Cosmology is a branch of astronomy. It studies the Universe as a whole.

Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Babylonians, Greeks, Indians, Egyptians, Chinese, Maya, and many ancient indigenous peoples of the Americas. In the past, astronomy included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars. Nowadays, professional astronomy is often said to be the same as astrophysics.

Professional astronomy is split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects. This data is then analyzed using basic principles of physics. Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. These two fields complement each other. Theoretical astronomy seeks to explain observational results and observations are used to confirm theoretical results.

Astronomy is one of the few sciences in which amateurs play an active role. This is especially true for the discovery and observation of transient events. Amateur astronomers have helped with many important discoveries, such as finding new comets.

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The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests that the Solar System formed from gas and dust orbiting the Sun. The theory was developed by Immanuel Kant and published in his Allgemeine Naturgeschichte und Theorie des Himmels ("Universal Natural History and Theory of the Heavens"), published in 1755 and then modified in 1796 by Pierre Laplace. Originally applied to the Solar System, the process of planetary system formation is now thought to be at work throughout the universe. The widely accepted modern variant of the nebular theory is the solar nebular disk model (SNDM) or solar nebular model. It offered explanations for a variety of properties of the Solar System, including the nearly circular and coplanar orbits of the planets, and their motion in the same direction as the Sun's rotation. Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded.

According to the nebular theory, stars form in massive and dense clouds of molecular hydrogen--giant molecular clouds (GMC). These clouds are gravitationally unstable, and matter coalesces within them to smaller denser clumps, which then rotate, collapse, and form stars. Star formation is a complex process, which always produces a gaseous protoplanetary disk (proplyd) around the young star. This may give birth to planets in certain circumstances, which are not well known. Thus the formation of planetary systems is thought to be a natural result of star formation. A Sun-like star usually takes approximately 1 million years to form, with the protoplanetary disk evolving into a planetary system over the next 10-100 million years. Read more...

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NGC 1300
Credit: NASA, ESA, and The Hubble Heritage Team STScI/AURA

NGC 1300 is a barred spiral galaxy about 61 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across; just slightly larger than our own galaxy, the Milky Way.

Astronomy News

28 July 2020 -
Astronomers at Pan-STARRS announce the discovery of a small near-Earth object (NEO) HLV2514, which is an Amor asteroid near Mars. The asteroid was first discovered in June 2020 by two 14-year-old Indian schoolgirls who were participating in a NASA project. (CNN)
20 April 2020 -
New data from the Atacama Large Millimeter Array and Hubble Space Telescope, published in the Nature Astronomy journal, suggests interstellar comet 2I/Borisov contains large amounts of carbon monoxide and hydrogen cyanide. The new findings suggest the object was formed in the cold outer region of its planetary system. (BBC)
7 April 2020 -
Astronomers report, via The Astronomer's Telegram, that comet C/2019 Y4 (ATLAS) appears to have disintegrated. (The Independent)
13 March 2020 - Planets beyond Neptune
Astronomers discover 139 new "minor planets" in the Solar System that are beyond the orbit of Neptune, which helps boost odds of finding Planet Nine. (NBC News)
28 February 2020 -
A meteor explodes over Croatia. The Croatian Astronomical Union say the meteor disintegrated at an altitude of at least 30 kilometers above sea level. The meteor was likely roughly 2 meters across. (Xinhuanet) (The Dubrovnik Times) (JPL)
27 February 2020 -
Astronomers discover the largest known explosion ever in the history of the Universe, which occurred in the Ophiuchus galaxy cluster. It replaces MS 0735.6+7421. As space and ground telescopes that study radio emissions improve (which are better than X-ray observations for detecting these), more similar explosions, or "giant radio fossils", may be found. (Phys) (CNN) (Astrophysics via arXiv at Cornell University)

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  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.

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