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 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 the 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.

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...)

Mercury is the first planet from the Sun and the smallest in the Solar System. It is a rocky planet with a trace atmosphere and a surface gravity slightly lower than that of Mars. The surface of Mercury is similar to Earth's Moon, being cratered, with an expansive rupes system generated from thrust faults, and bright ray systems, formed by ejecta. Its largest crater, Caloris Planitia, has a diameter of 1,550 km (960 mi), which is about one-third the diameter of the planet (4,880 km or 3,030 mi). Being the most inferior orbiting planet, it always appears close to the Sun in Earth's sky, as either a "morning star" or an "evening star". It is the planet with the highest delta-v required for travel from Earth, as well as to and from the other planets in the Solar System.

Mercury's sidereal year (88.0 Earth days) and sidereal day (58.65 Earth days) are in a 3:2 ratio, in a spin–orbit resonance. Consequently, one solar day (sunrise to sunrise) on Mercury lasts for around 176 Earth days, or twice Mercury's sidereal year. This means that one side of Mercury will remain in sunlight for one Mercurian year of 88 Earth days; while during the next orbit, that side will be in darkness all the time until the next sunrise after another 88 Earth days. Above the planet's surface is an extremely tenuous exosphere and a faint magnetic field just strong enough to deflect solar winds. Combined with its high orbital eccentricity, the planet's surface has widely varying sunlight intensity and temperature, with the equatorial regions ranging from −170 °C (−270 °F) at night to 420 °C (790 °F) during sunlight. Despite being the closest planet to the sun, it is the second hottest after Venus, lacking an atmosphere to trap heat. Due to its very small axial tilt, the planet's poles are permanently shadowed. This strongly suggests that water ice could be present in the craters. (Full article...)

• ... that although color-blind, Nicholas U. Mayall was better able to detect faint galaxies than most other astronomers?
• ... that The Man in the Moone, a 1638 book by the English bishop Francis Godwin, is considered one of the first science fiction books?
• ... that the galaxy Markarian 501 produces very high energy gamma rays?
• ... that the Near-Earth object and Mars-crosser asteroid 2007 WD5 is estimated to have a 1-in-75 chance of colliding with Mars?
• ... that hydroxyl megamasers were used to make the first detection of Zeeman splitting in a galaxy other than the Milky Way?

• ... that scientists have discovered a planetary system that can be described as "inside-out"?
• ... that novelist Hal Clement created the planet Mesklin in 1953 based on the real-world suspected detection of an extrasolar planet?
• ... that TOI-1853 b is a Neptune-sized exoplanet that is denser than steel?
• ... that Na drugą planetę, published in 1895 as one of the earliest Polish science-fiction novels, was later criticized by communist-era censors for its perceived "adoration for America"?
• ... that two competing hypotheses seek to explain the unusual orbit of the exoplanet Nu Octantis Ab?
• ... that Pisces VII, a dwarf satellite galaxy, is the first galaxy in the Local Group to be discovered by an amateur astronomer?

GG Tauri, often abbreviated as GG Tau, is a quadruple or quintuple star system in the constellation Taurus at a distance of about 450 light years (140 parsecs) away. Image is an artist's impression of the disk surrounding GG Tauri A and B.

15 October 2026 –

Astronomers discover the first green star, WD J1330+6435, according to a study published by RAS Techniques and Instruments. (Popular Science)

6 October 2026 –

Belgian physicist Francis Halzen from the University of Wisconsin–Madison is awarded the Nobel Prize in Physics for his "decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin". (CNN)

16 September 2026 – Discoveries of exoplanets

Astronomers confirm the existence of Elias 2-24 b, the youngest known exoplanet, which is less than one million years old and located approximately 450 light-years from Earth. The discovery was observed through the W.M. Keck Observatory in Mauna Kea, Hawaii, U.S., using a coronagraph. (Space.com)

12 August 2026 – MoM-BH*-1

Astronomers studying a little red dot found by the James Webb Space Telescope announce in Nature the discovery of the first black hole star. The first object classed as such, [[MoM-BH;12 August 2026 – MoM-BH*-1

-1]], in the constellation of Cetus, is the size of the Solar System and emits a light that outshines its host galaxy. (The Guardian) (PopSci)

16 July 2026 –

Astronomers report the first observationally confirmed atmosphere around a rocky exoplanet within its star's habitable zone, after detecting helium escaping from the upper atmosphere of LHS 1140 b, a super-Earth approximately 49 light-years from Earth. (Space.com)

15 July 2026 – Discoveries of exoplanets

Astronomers directly image the exoplanet Beta Pictoris d next to its star, located 63 light-years away, using NASA's James Webb Space Telescope and European Southern Observatory's Very Large Telescope. It is also reported to be fainter than its sibling Beta Pictoris b. The discovery is published in the The Astrophysical Journal. (ABC News) (Space.com)

• 1 October 2003 – The Japan Aerospace Exploration Agency is formed from a merger of three previous Japanese space agencies
• 4 October 1957 – The first artificial satellite, Sputnik 1, is launched into orbit by the Soviet Union, triggering the Space Race
• 5 October 2012 – CSIRO's Australian Square Kilometre Array Pathfinder (ASKAP) telescope, which detected the first Odd radio circle in 2019, has its first light.
• 15 October 1997 – The Cassini space probe launches and is active in space for nearly 20 years
• 15 October 2003 – The People's Republic of China becomes the third nation to send a human into space when Yang Liwei is launched into outer space aboard Shenzhou 5
• 24 October 1946 – First motion pictures of Earth are taken from a V-2 rocket
• 29 October 1991 – Galileo probe flyby of Asteroid Gaspra
• 31 October 1961 – Murriyang, CSIRO's 64 m Parkes radio telescope at the Parkes Observatory on Wiradjuri Country in NSW, was inaugurated.