Portal:Astronomy

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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, Nubians, Iranians, 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.

Amateurs play an active role in astronomy. It is one of the few sciences in which this is the case. 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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SDO's Ultra-high Definition View of 2012 Venus Transit (171 Angstrom Full Disc).jpg

A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus can be seen from Earth as a small black dot moving across the face of the Sun. The duration of such transits is usually several hours (the transit of 2012 lasted 6 hours and 40 minutes). A transit is similar to a solar eclipse by the Moon. While the diameter of Venus is more than three times that of the Moon, Venus appears smaller, and travels more slowly across the face of the Sun, because it is much farther away from Earth.

Transits of Venus are among the rarest of predictable astronomical phenomena. They occur in a pattern that generally repeats every 243 years, with pairs of transits eight years apart separated by long gaps of 121.5 years and 105.5 years. The periodicity is a reflection of the fact that the orbital periods of Earth and Venus are close to 8:13 and 243:395 commensurabilities. Read more...

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Cassiopeia A
Credit: NASA/JPL-Caltech

Cassiopeia A (Cas A) is a supernova remnant in the constellation Cassiopeia and the brightest astronomical radio source in the sky, with a flux of 2720 Jy at 1 GHz. The supernova occurred approximately 11,000 light-years (3.4 kpc) away in the Milky Way.

Astronomy News

7 October 2019 –
Astronomers announce the discovery of 20 new moons around Saturn, adding to the 62 previously known. The new moons comprise 17 retrograde moons in the Norse group and three prograde moons, two of which belong to the Inuit group. (Phys.org)
12 September 2019 – Interstellar objects
C/2019 Q4 (Borisov), a second interstellar comet after ʻOumuamua in 2017, is discovered by an amateur astronomer. (BBC)
19 August 2019 –
Astronomers led by a team from McGill University in Montreal announce the detection of eight new repeating fast radio bursts (FRBs) using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope. The astronomers report they also found complex morphologies and downward-drifting sub-bursts in some of the eight new FRBs. (Phys.org)
1 August 2019 – List of nearest exoplanets
Astronomers from the Max Planck Institute for Astronomy announce the discovery of red dwarf star GJ 357 and its three confirmed exoplanets in the Hydra constellation, one of which (GJ 357 d) is highly likely to be a super-Earth planet located in the system's circumstellar habitable zone where life can exist. The discovery was made using NASA's Transiting Exoplanet Survey Satellite (TESS). (The Independent)
17 July 2019 –
Astronomers rule out the chances of ~30-meter asteroid 2006 QV89's impacting Earth in September 2019 by eliminating the possibility of its passing through an area where it would have to be if it were on an impacting orbit. Prior to this, the asteroid had been given a one-in-7,000 chance of impacting Earth. (phys.org)
31 January 2019 –
Astronomers announce, through the Monthly Notices of the Royal Astronomical Society journal, the accidental discovery of dwarf spheroidal galaxy Bedin I in the Pavo constellation in September 2018. (Space Telescope)

December anniversaries

  • 14 December 1962 - Mariner 2 becomes the first space probe to perform a flyby of a planet, when it passes within 35,000 kilometers of Venus
  • 19 December 2013 - Gaia was launched. Its mission is to study billions of stars in the Milky Way
  • 21 December 1968 - Apollo 8, the first crewed spacecraft to leave Earth orbit, reach the Moon, orbit it, and return safely to Earth, is launched

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Astronomical events

All times UT unless otherwise specified.

5 December, 04:07 Moon at apogee
12 December, 05:12 Full moon
14 December, 16:00 Geminids peak
18 December, 20:27 Moon at perigee
22 December, 04:19 Earth southern solstice
26 December, 05:18 New moon and annular solar eclipse
26 December, 07:30 Moon occults Jupiter
27 December, 14:31 Moon occults Pluto
27 December, 18:25 Jupiter at conjunction, occultation
29 December, 01:31 Moon occults Venus

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