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: ἀστρονομία) 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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Known objects in the Kuiper belt beyond the orbit of Neptune. (Scale in AU; epoch as of January 2015.)
  Sun
  Jupiter trojans
  Giant planets:
  Centaurs
  Neptune trojans
  Resonant Kuiper belt
  Classical Kuiper belt
  Scattered disc
Distances but not sizes are to scale
Source: Minor Planet Center, www.cfeps.net and others

The Kuiper belt (/ˈkpər, ˈkʊɪ-/), occasionally called the Edgeworth–Kuiper belt, is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger – 20 times as wide and 20–200 times as massive. Like the asteroid belt, it consists mainly of small bodies or remnants from when the Solar System formed. While many asteroids are composed primarily of rock and metal, most Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water. The Kuiper belt is home to three officially recognized dwarf planets: Pluto, Haumea and Makemake. Some of the Solar System's moons, such as Neptune's Triton and Saturn's Phoebe, may have originated in the region.

The Kuiper belt was named after Dutch-American astronomer Gerard Kuiper, though he did not predict its existence. In 1992, minor planet (15760) Albion was discovered, the first Kuiper belt object (KBO) since Pluto and Charon. Since its discovery, the number of known KBOs has increased to thousands, and more than 100,000 KBOs over 100 km (62 mi) in diameter are thought to exist. The Kuiper belt was initially thought to be the main repository for periodic comets, those with orbits lasting less than 200 years. Studies since the mid-1990s have shown that the belt is dynamically stable and that comets' true place of origin is the scattered disc, a dynamically active zone created by the outward motion of Neptune 4.5 billion years ago; scattered disc objects such as Eris have extremely eccentric orbits that take them as far as 100 AU from the Sun. Read more...

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Cassiopeia A
Cr: Digitized Sky Survey, ESA/ESO/NASA FITS Liberator

Orion's Belt or The Belt of Orion is an asterism in the constellation Orion. It consists of the three bright stars: ζ Ori (Alnitak), ε Ori (Alnilam), and δ Ori (Mintaka).

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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