The Astronomy Portal


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

Astronomy (from Greek: ἀστρονομία, 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 that 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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Location of Tau Ceti

Tau Ceti, Latinized from τ 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...)

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Flaming Star Nebula
Credit: User:Hewholooks

IC 405, also Sharpless 229 (Sh2-229), Caldwell 31 and The Flaming Star Nebula, is an emission/reflection nebula and a Caldwell object in the constellation Auriga, surrounding the bluish star AE Aurigae. It shines at magnitude +6.0. The nebula is about 5 light-years across. This is a white light image of the Flaming Star Nebula showing the "smoke" of reflection nebula.

Astronomy News

17 February 2021 – Discoveries of exoplanets
Astronomers announce the discovery of HD 110082 b, a sub-Neptune exoplanet that is three times larger than Earth and which orbits a relatively young star. (
1 December 2020 – 2020 SO
Unknown astronomical object 2020 SO makes its closest approach to Earth at a perigee distance of approximately 0.13 lunar distances (50,000 km; 31,000 mi). Researchers, who discovered 2020 SO on September 17, 2020, are still unsure whether the object is a small near-Earth asteroid or an artificial object. The booster of Surveyor 2's Atlas-Centaur rocket, launched by NASA in 1966, is suspected by the Jet Propulsion Laboratory. (CNET)

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Astronomical events

All times UT unless otherwise specified.

5 May, 01:30 Eta Aquariids peak
11 May, 19:00 New moon
11 May, 21:54 Moon at apogee
12 May, 22:03 Moon occults Venus
17 May, 05:59 Mercury at greatest eastern elongation
26 May, 01:52 Moon at perigee
26 May, 11:19 Full moon and total lunar eclipse


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