Portal:Astronomy
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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: ?, 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 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 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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The Venusian symbol, a circle with a small equal-armed cross beneath it

Venus is the second planet from the Sun. It is named after the Roman goddess of love and beauty. As the brightest natural object in Earth's night sky after the Moon, Venus can cast shadows and can be, on rare occasions, visible to the naked eye in broad daylight. Venus lies within Earth's orbit, and so never appears to venture far from the Sun, either setting in the west just after dusk or rising in the east a little while before dawn. Venus orbits the Sun every 224.7 Earth days. It has a synodic day length of 117 Earth days and a sidereal rotation period of 243 Earth days. As a consequence, it takes longer to rotate about its axis than any other planet in the Solar System, and does so in the opposite direction to all but Uranus. This means the Sun rises in the west and sets in the east. Venus does not have any moons, a distinction it shares only with Mercury among the planets in the Solar System.

Venus is a terrestrial planet and is sometimes called Earth's "sister planet" because of their similar size, mass, proximity to the Sun, and bulk composition. It is radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is about 92 times the sea level pressure of Earth, or roughly the pressure at 900 m (3,000 ft) underwater on Earth. Even though Mercury is closer to the Sun, Venus has the hottest surface of any planet in the Solar System, with a mean temperature of 737 K (464 °C; 867 °F). Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. It may have had water oceans in the past, but these will have vaporized as the temperature rose under a runaway greenhouse effect. The water has probably photodissociated, and the free hydrogen has been swept into interplanetary space by the solar wind because of the lack of a planetary magnetic field. (Full article...)

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Ngc2392.jpg
Credit: NASA / ESA / Andrew Fruchter (STScI) / ERO team (STScI + ST-ECF)

The Eskimo Nebula (NGC 2392), also known as the Clown-faced Nebula, Lion Nebula or Caldwell 39, is a bipolar planetary nebula (PN) discovered by astronomer William Herschel in 1787. Image of NGC 2392, the Eskimo Nebula is by HST in 1999.

Astronomy News

26 May 2021 - May 2021 lunar eclipse
A total lunar eclipse occurs, the second-shortest of the 21st century, with totality lasting for only 14 minutes. Nicknamed the Super Flower Blood Moon, the eclipse was visible over the Pacific Ocean and Oceania, with South and East Asia seeing the eclipse at moonrise, and the Americas seeing the eclipse at moonset. (Space.com)
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. (Phys.org)

July anniversaries

Space-related Portals

Astronomical events

All times UT unless otherwise specified.

3 July, 11:41 Close approach of Venus and M44
4 July, 19:59 Mercury at greatest western elongation of 21.6 degrees from the Sun
5 July, 14:48 Moon at apogee
6 July, 02:59 Earth at aphelion
7 July, 04:39 Conjunction of the Moon and Mercury
10 July, 01:17 New moon
21 July, 10:24 Moon at perigee
24 July, 02:37 Full moon
28 July, 03:17 Peak of Delta Aquariids meteor shower

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  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.

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