Portal:Astronomy

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...)

Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker and denser than Earth and any other rocky body in the Solar System. Its atmosphere is composed of mostly carbon dioxide (CO₂), with a global sulfuric acid cloud cover and no liquid water. At the mean surface level the atmosphere reaches a temperature of 737 K (464 °C; 867 °F) and a pressure 92 times greater than Earth's at sea level, turning the lowest layer of the atmosphere into a supercritical fluid. Venus is the third brightest object in Earth's sky, after the Moon and the Sun, and, like Mercury, appears always relatively close to the Sun, either as a "morning star" or an "evening star", resulting from orbiting closer (inferior) to the Sun than Earth.

The orbits of Venus and Earth make the two planets approach each other in synodic periods of 1.6 years. In the course of this Venus comes closer to Earth than any other planet, while on average Mercury stays closer to Earth (and any other planet) due to its more inferior orbit. Venus is frequently used for gravity assists, as a waypoint for interplanetary flights. Venus has no moons and has a very slow retrograde rotation about its axis, a result of competing forces of solar tidal locking and differential heating of Venus's massive atmosphere. As a result a Venusian day is 116.75 Earth days long, about half a Venusian solar year, which is 224.7 Earth days long. (Full article...)

• ... that Caroline Moore was 14 years old when she discovered supernova 2008ha?
• ... that although Charles Messier discovered the galaxy M91 in 1781, it was added to his catalogue only two centuries later?
• ... that the fall of the Neuschwanstein meteorite in 2002 was observed by the European Fireball Network and outdoor witnesses through most of Central Europe?
• ... that AG Pegasi has been described as the slowest nova ever recorded?

• ... that a profile of artist Mark Hearld said his "wrens and squirrels, field mice and owls" help a child care about the planet better than telling them it is burning?
• ... that the star TRAPPIST-1 has seven planets, several of which may have temperatures that would allow the existence of liquid water (artist's impression depicted)?
• ... that novelist Hal Clement created the planet Mesklin in 1953 based on the real-world suspected detection of an extrasolar planet?
• ... that the active galaxy 3C 120 was given the variable-star designation BW Tauri because of its variability in the visible spectrum?
• ... that in early depictions of Uranus in fiction, the planet was portrayed as solid
• ... that 1ES 1927+654, a galaxy in Draco, exhibited such extreme nuclear activity that it challenged conventional models of black-hole environments?

Hubble Space Telescope image of NGC 6052, discovered on 11 June 1784 by William Herschel. The two components of NGC 6052 are designated NGC 6052A and NGC 6052B are attracted by each other's gravity, have collided and are interacting with each other.

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• 2 June 1966 – Surveyor 1 lands on the Moon, first US spacecraft to do so
• 3 June 1966 – Gemini 9 (Gemini Titan 9A) launch from Cape Canaveral, Florida
• 19 June 1976 – The Viking 1 orbiter arrives in Mars orbit
• 24 June 2004 – First private spaceflight, SpaceShipOne piloted by Mike Melvill
• 27 June 1996 – Galileo probe, flyby of Ganymede (Jupiter's largest moon)
• 30 June 2001 – The NASA Explorer mission, MAP (Microwave Anisotropy Probe), is launched to measure the temperature of cosmic background radiation (remnant heat from the Big Bang)