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The Astronomy Portal

Introduction

Astronomy (from Greek: ?, literally meaning the science that studies the laws of the stars) 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. (Full article...)

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Tau Ceti, Latinized from ? Ceti, is a single star in the constellation Cetus that is spectrally similar to the Sun, although it has only about 78% of the Sun's mass. At a distance of just under 12 light-years (3.7 parsecs) from the Solar System, it is a relatively nearby star and the closest solitary G-class star. The star appears stable, with little stellar variation, and is metal-deficient.

Observations have detected more than ten times as much dust surrounding Tau Ceti as is present in the Solar System. Since December 2012, there has been evidence of at least four planets--all confirmed being super-Earths--orbiting Tau Ceti, with two of these being potentially in the habitable zone. There are an additional four unconfirmed planets, one of which is a Jovian planet between 3 and 20 AU from the star. Because of its debris disk, any planet orbiting Tau Ceti would face far more impact events than Earth. Despite this hurdle to habitability, its solar analog (Sun-like) characteristics have led to widespread interest in the star. Given its stability, similarity and relative proximity to the Sun, Tau Ceti is consistently listed as a target for the Search for Extra-Terrestrial Intelligence (SETI) and appears in some science fiction literature. (Full article...)

List of featured articles

Did you know - show different entries

... that Oscar Monnig donated one of the largest private collections of meteorites to Texas Christian University?
... that at first light in 1987, the William Herschel Telescope was the third largest single optical telescope in the world, and is still the second largest in Europe?
... that a Bok globule is a dark cloud of dense dust and gas, first observed by astronomer Bart Bok in the 1940s, in which star formation is taking place within the H II region?
... that the aerial telescope is a type of very long focal length refracting telescope built in the second half of the 17th century that did not use a tube?
... that the galaxy pair Arp 147 contains a ring of nine black holes?

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Subcategories

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WikiProjects

WikiProject Astronomy	WikiProject Solar System



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Credit: NASA / JPL-Caltech / Space Science Institute

Mimas is a moon of Saturn. It was discovered in 1789 by William Herschel, after whom the large crater in the image is named. It is the twentieth-largest moon in the Solar System, and the smallest astronomical body that is known to be rounded in shape because of self-gravitation. This photograph of Mimas was taken by the unmanned spacecraft Cassini in 2010.

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Astronomy News

4 November 2020 - SGR 1935+2154: Astronomers announce the discovery of the first fast radio burst (FRB) signal detected in the Milky Way galaxy. The signal is believed to be coming from a magnetar. (The Independent)
13 October 2020 -: As Mars lines up with Earth and the Sun, it is expected to shine at its biggest and brightest during the night. (ITV) (NBC News)
7 October 2020 -: Starman, a Tesla Roadster that was launched on a Falcon Heavy rocket three years ago by Elon Musk, makes its closest approach to Mars at a distance of 0.05 astronomical units. (CNN)
28 September 2020 - Water on Mars: Scientists in a paper published to Nature Astronomy confirm the existence of four underground saltwater lakes spread out over 75,000 square kilometres (29,000 sq mi) near Mars' south pole. Depending on their salt content, these lakes could be potential holders of life. (Nature)
23 September 2020 -: Astronomers announce the crescent shadow of Messier 87's supermassive black hole is wobbling. Back in April 2019, the Event Horizon Telescope captured the crescent shadow of the [[Messier 87#Supermassive black hole M87;23 September 2020 -; |black hole]], making it the first image ever taken of a black hole. (Sci News)
22 September 2020 -: Astronomers find glowing auroras around 67P/Churyumov-Gerasimenko. This is the first comet discovered to have them. (CBS News)

November anniversaries

2 November 1917 – The Hooker Telescope at Mount Wilson Observatory, the largest telescope in the world from 1917 until 1948, sees first light
14 November 1971 – Unmanned probe Mariner 9 arrives at Mars and becomes the first spacecraft to orbit around another planet
18 November 1989 – Explorer 66, a satellite designed to study cosmic microwave background radiation and supply evidence in support of the Big Bang theory, is launched
20 November 1998 – Zarya, the first module of the International Space Station, is launched
28 November 1967 – PSR B1919+21 becomes the first pulsar to be observed when it is discovered by Jocelyn Bell Burnell and Antony Hewish

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Space-related Portals

Study Guides

These books may be in various stages of development. See also the related Science and Mathematics bookshelves.

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Solar System

Astronomical events

All times UT unless otherwise specified.

10 November, 16:59	Mercury at greatest western elongation
14 November, 11:48	Moon at perigee
15 November, 05:07	New moon
17 November, 11:24	Leonids peak
27 November, 00:29	Moon at apogee
30 November, 09:44	Full moon and penumbral lunar eclipse