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Portal:Astronomy

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Introduction

A man sitting on a chair mounted to a moving platform, staring through a large telescope.
Percival Lowell observing Venus from the Lowell Observatory telescope in 1914

Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, meteoroids, asteroids, 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 beyond 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 Egyptians, Babylonians, Greeks, Indians, 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.

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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White glowing ball with black sunspots
The Sun, viewed through a clear solar filter

The Sun is the star at the center of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light and infrared radiation with 10% at ultraviolet energies. It is by far the most important source of energy for life on Earth. The Sun has been an object of veneration in many cultures. It has been a central subject for astronomical research since antiquity.

The Sun orbits the Galactic Center at a distance of 24,000 to 28,000 light-years. From Earth, it is astronomical unit (1.496×108 km) or about 8 light-minutes away. Its diameter is about 1,391,400 km (864,600 mi), 109 times that of Earth. Its mass is about 330,000 times that of Earth, making up about 99.86% of the total mass of the Solar System. Roughly three-quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron. (Full article...)

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Credit: NASA JPL CalTech

WD 0145+234 is a white dwarf star approximately 95 ly (29 pc) from Earth in the constellation of Aries that has been associated with studies suggesting that a very large exoasteroid near the star was substantially disrupted, resulting in a considerable amount of dust and debris around the star. It was discovered in 2019.

Astronomy News

15 July 2024 – Mare Tranquillitatis pit
In the journal Nature Astronomy, American and Italian scientists announce the discovery of a lunar cave, approximately 250 miles (400 km) from the landing site of Apollo 11. (AP) (Nature Astronomy)

October anniversaries

Astronomical events

All times UT unless otherwise specified.

2 October, 18:46 New moon and annular solar eclipse
2 October, 19:40 Moon at apogee
14 October, 18:13 Moon occults Saturn
15 October, 17:32 Moon occults Neptune
17 October, 00:46 Moon at perigee
17 October, 11:26 Full moon
21 October, 05:58 Orionids peak
29 October, 22:50 Moon at apogee

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