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...)

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General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second order partial differential equations.

Newton's law of universal gravitation, which describes classical gravity, can be seen as a prediction of general relativity for the almost flat spacetime geometry around stationary mass distributions. Some predictions of general relativity, however, are beyond Newton's law of universal gravitation in classical physics. These predictions concern the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light, and include gravitational time dilation, gravitational lensing, the gravitational redshift of light, the Shapiro time delay and singularities/black holes. So far, all tests of general relativity have been shown to be in agreement with the theory. The time-dependent solutions of general relativity enable us to talk about the history of the universe and have provided the modern framework for cosmology, thus leading to the discovery of the Big Bang and cosmic microwave background radiation. Despite the introduction of a number of alternative theories, general relativity continues to be the simplest theory consistent with experimental data. (Full article...)

• ... that lenticular galaxy NGC 1553 is located at the center of the Dorado Group, and has a spiral feature that is only visible in X-rays?
• ... that giant diffuse galaxies, located in the centre of galaxy clusters, often possess a halo of devoured star matter extending as far out as 3 million light years?
• ... that the giant pulses of PSR B1937+21, the first discovered millisecond pulsar, are the brightest radio emission ever observed?
• ... that the star BX Circini is thought to have formed from the merger of two white dwarfs?
• ... that when astronomer Lacaille originally charted the constellation Caelum, it was recognized as an "engraver's chisel"?
• ... that the gamma-ray burst GRB 080319B was visible to the naked eye even though it was 7.5 billion light year away (z=0.937)?

• ... that examples of artificial planets in science fiction include Riverworld, the Well World, and the Death Star?
• ... that it took five years of observations to find the planet orbiting the star HD 175167?
• ... that Nandivada Rathnasree, who ran Delhi's planetarium, proposed that astronomers could be taught using India's stone-built observatories?
• ... that the Passive Seismic Experiment Package recorded one of the first instances of humans littering on another planetary body?
• ... that Jessen's icosahedron has been used for both the "Skwish" children's toy and a NASA proposal for a "super ball bot" to cushion space landers on other planets?
• ... that in early depictions of Uranus in fiction, the planet was portrayed as solid

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Messier 67 (also known as M67 or NGC 2682) is an open cluster in the southern, equatorial half of Cancer. It was discovered by Johann Gottfried Koehler in 1779. Image of Messier 67 (SDSS, optical and near-infrared).

20 February 2024 –

Astronomers identify the most luminous object ever observed, QSO J0529-4351, a quasar that accretes around one solar mass per day. (The Guardian) (Nature.com)

24 November 2023 –

Astronomers at the Telescope Array Project in Utah, United States, observe the second largest cosmic ray ever detected, the so-called Amaterasu particle, with an energy of 244 EeV. (Cosmos Magazine)

• 2 April 1968 – The epic science fiction film, 2001: A Space Odyssey is released
• 3 April 2014 – NASA announces that the Cassini orbiter has found evidence of an underground body of water on Enceladus, a moon of Saturn
• 7 April 2001 – Mars Odyssey orbiter is launched to map and search for water on Mars
• 12 April 1961 – Cosmonaut Yuri Gagarin becomes the first human to enter outer space when he is launched into orbital flight in Vostok 1
• 19 April 1971 – The first space station, Salyut 1, is launched into orbit
• 24 April 1990 – The Hubble Space Telescope, a powerful research tool and public relations boon for astronomy, is launched into orbit