Astronomy 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, 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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Apollo 8 (December 21–27, 1968) was the first crewed spacecraft to leave low Earth orbit and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times without landing, and then departed safely back to Earth. These three astronauts—Frank Borman, James Lovell, and William Anders—were the first humans to witness and photograph the far side of the Moon and an Earthrise.

Apollo 8 launched on December 21, 1968, and was the second crewed spaceflight mission flown in the United States Apollo space program after Apollo 7, which stayed in Earth orbit. Apollo 8 was the third flight and the first crewed launch of the Saturn V rocket, and was the first human spaceflight from the Kennedy Space Center, located adjacent to Cape Kennedy Air Force Station in Florida. (Full article...)

• ... that Oscar Monnig donated one of the largest private collections of meteorites to Texas Christian University?
• ... that at first light in 1987, the William Herschel Telescope was the third largest single optical telescope in the world, and is still the second largest in Europe?
• ... that a Bok globule is a dark cloud of dense dust and gas, first observed by astronomer Bart Bok in the 1940s, in which star formation is taking place within the H II region?
• ... that the aerial telescope is a type of very long focal length refracting telescope built in the second half of the 17th century that did not use a tube?
• ... that the galaxy pair Arp 147 contains a ring of nine black holes?

• ... that The City in the Middle of the Night, a 2019 climate-fiction novel by Charlie Jane Anders, is set on a tidally locked planet?
• ... that in early depictions of Uranus in fiction, the planet was portrayed as solid
• ... that it took five years of observations to find the planet orbiting the star HD 175167?
• ... 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 the Passive Seismic Experiment Package recorded one of the first instances of humans littering on another planetary body?
• ... that King Gizzard & the Lizard Wizard's "cli-fi" thrash metal album addresses a mix of current ecological threats and attempts to find another planet to live on?

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Gamma-ray burst progenitors are the types of celestial objects that can emit gamma-ray bursts (GRBs). GRBs show an extraordinary degree of diversity. They can last anywhere from a fraction of a second to many minutes. Image is Eta Carinae, in the constellation of Carina, one of the nearer candidates for a hypernova.

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)

14 June 2023 –

Astronomers report that the presence of phosphates on Enceladus, moon of the planet Saturn, has been detected, completing the discovery of all the basic chemical ingredients for life on the moon. (New York Times)

12 June 2023 – Discoveries of exoplanets

Astronomers announce in the journal Nature Astronomy the discovery of BEBOP-1c, an exoplanet orbiting the binary star system, TOI-1338. The system is the second discovered to have more than one circumbinary planet. (Space.com)

• 7 December 1972 – The “Blue Marble” photograph is taken by the Apollo 17 crew
• 8 December 1992 – Galileo completes the second Earth flyby
• 14 December 1962 – Mariner 2 becomes the first space probe to perform a flyby of a planet, when it passes within 35,000 kilometers of Venus
• 17 December 1917 – “2001: A Space Odyssey” science fiction author Arthur C. Clarke is born
• 19 December 2013 – Gaia is launched for the mission to study billions of stars in the Milky Way
• 21 December 1968 – Apollo 8, is launched with the first crewed spacecraft to leave Earth orbit, reach the Moon, orbit it, and return safely to Earth
• 27 December 1571 – Astronomer, mathematician, and astrologer Johannes Kepler is born