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Topic Review

Yellow Supergiant Star

A yellow supergiant (YSG) is a star, generally of spectral type F or G, having a supergiant luminosity class (e.g. Ia or Ib). They are stars that have evolved away from the main sequence, expanding and becoming more luminous. Yellow supergiants are smaller than red supergiants; naked eye examples include Polaris. Many of them are variable stars, mostly pulsating Cepheids such as δ Cephei itself.

2.9K
03 Nov 2022

Topic Review

Pegasus, the winged horse of Greek mythology, is a prominent constellation in the northern sky, known for its distinctive "Great Square" asterism. As one of the 48 constellations cataloged by the ancient Greek astronomer Ptolemy, Pegasus has a rich cultural and astronomical significance. Its association with the mythical creature Pegasus, ridden by heroes such as Perseus and Bellerophon, adds to its allure and makes it a captivating subject for stargazers.

2.8K
15 Mar 2024

Topic Review

Traditional Chinese Star Names

Traditional Chinese star names (Chinese: 星名, xīng míng) are the names of stars used in ancient Chinese astronomy and astrology. Most of these names are enumerations within the respective Chinese constellations, but a few stars have traditional proper names.

2.8K
29 Sep 2022

Topic Review

Centaur (Minor Planet)

Centaurs are small solar system bodies with a semi-major axis between those of the outer planets. They generally have unstable orbits because they cross or have crossed the orbits of one or more of the giant planets; almost all their orbits have dynamic lifetimes of only a few million years, but there is one centaur, (514107) 2015 BZ509, which may be in a stable (though retrograde) orbit. Centaurs typically behave with characteristics of both asteroids and comets. They are named after the mythological centaurs that were a mixture of horse and human. It has been estimated that there are around 44,000 centaurs in the Solar System with diameters larger than 1 kilometer. The first centaur to be discovered, under the definition of the Jet Propulsion Laboratory and the one used here, was 944 Hidalgo in 1920. However, they were not recognized as a distinct population until the discovery of 2060 Chiron in 1977. The largest confirmed centaur is 10199 Chariklo, which at 260 kilometers in diameter is as big as a mid-sized main-belt asteroid, and is known to have a system of rings. It was discovered in 1997. However, the lost centaur 1995 SN55 may be somewhat larger. No centaur has been photographed up close, although there is evidence that Saturn's moon Phoebe, imaged by the Cassini probe in 2004, may be a captured centaur that originated in the Kuiper belt. In addition, the Hubble Space Telescope has gleaned some information about the surface features of 8405 Asbolus. (As of 2008), three centaurs have been found to display comet-like comas: 2060 Chiron, 60558 Echeclus, and 166P/NEAT. Chiron and Echeclus are therefore classified as both asteroids and comets. Other centaurs, such as 52872 Okyrhoe, are suspected of having shown comas. Any centaur that is perturbed close enough to the Sun is expected to become a comet.

2.7K
25 Nov 2022

Topic Review

1769 Transit of Venus Observed from Tahiti

On June 3, 1769, British navigator Captain James Cook, British naturalist Joseph Banks, British astronomer Charles Green and Swedish naturalist Daniel Solander recorded the transit of Venus on the island of Tahiti during Cook's first voyage around the world. During a transit, Venus appears as a small black disc travelling across the Sun. This unusual astronomical phenomenon takes place in a pattern that repeats itself every 243 years. It includes two transits that are eight years apart, separated by breaks of 121.5 and 105.5 years. These men, along with a crew of scientists, were commissioned by the Royal Society of London for the primary purpose of viewing the transit of Venus. Not only would their findings help expand scientific knowledge, it would help with navigation by accurately calculating the observer's longitude. At this time, longitude was difficult to determine and not always precise. A "secret" mission that followed the transit included the exploration of the South Pacific to find the legendary Terra Australis Incognita or "unknown land of the South."

2.7K
30 Sep 2022

Topic Review

Ursa Minor, Latin for "Lesser Bear," is a constellation in the northern celestial hemisphere. It is best known for containing the North Star, Polaris, which marks the position of the north celestial pole and aids in navigation. Despite its small size and dim stars, Ursa Minor holds significant cultural and navigational importance throughout human history.

2.7K
15 Mar 2024

Topic Review

Centaurus, a prominent southern hemisphere constellation, is one of the largest and most recognizable constellations in the night sky. Named after the centaur Chiron from Greek mythology, Centaurus features the bright Alpha Centauri system, one of the closest star systems to Earth.

2.6K
29 Feb 2024

Topic Review

List of Objects at Lagrangian Points

This is a list of known objects which occupy, have occupied, or are planned to occupy any of the five Lagrangian points of two-body systems in space.

2.6K
08 Nov 2022

Topic Review

Cassiopeia, named after the queen in Greek mythology, is a prominent constellation in the northern celestial hemisphere. Known for its distinctive "W" or "M" shape, depending on its orientation in the sky, Cassiopeia is easily recognizable and has been a subject of fascination for astronomers and stargazers throughout history.

2.6K
29 Feb 2024

Topic Review

Hercules is a prominent constellation in the northern celestial hemisphere, named after the legendary hero from Greek mythology known for his incredible strength and courage. It is the fifth-largest of the 88 modern constellations.

2.6K
15 Mar 2024

Topic Review

Sagittarius, often referred to as "the Archer," is a prominent constellation in the southern celestial hemisphere, renowned for its association with Greek mythology and the mythical centaur Chiron. Positioned along the Milky Way, Sagittarius hosts a wealth of celestial wonders, including the galactic center and numerous star clusters.

2.6K
15 Mar 2024

Topic Review

Gemini, named after the Latin word for "twins," is a prominent constellation in the northern celestial hemisphere. Representing the twins Castor and Pollux from Greek mythology, Gemini is known for its two bright stars that mark the heads of the twins.

2.6K
15 Mar 2024

Topic Review

Lunar Outpost (NASA)

A lunar outpost is a concept of a permanent or semi-permanent presence of humans on the Moon, a moonbase, by the United States space administration NASA. NASA requested an increase in the 2020 budget of $1.6 billion, in order to make another crewed mission to the Moon by 2025 (originally 2024), followed by a sustained presence on the Moon by 2028.

2.5K
23 Nov 2022

Topic Review

Volcanology of Mars

Volcanic activity, or volcanism, has played a significant role in the geologic evolution of Mars. Scientists have known since the Mariner 9 mission in 1972 that volcanic features cover large portions of the Martian surface. These features include extensive lava flows, vast lava plains, and the largest known volcanoes in the Solar System. Martian volcanic features range in age from Noachian (>3.7 billion years) to late Amazonian (< 500 million years), indicating that the planet has been volcanically active throughout its history, and some speculate it probably still is so today. Both Earth and Mars are large, differentiated planets built from similar chondritic materials. Many of the same magmatic processes that occur on Earth also occurred on Mars, and both planets are similar enough compositionally that the same names can be applied to their igneous rocks and minerals. Volcanism is a process in which magma from a planet's interior rises through the crust and erupts on the surface. The erupted materials consist of molten rock (lava), hot fragmental debris (tephra or ash), and gases. Volcanism is a principal way that planets release their internal heat. Volcanic eruptions produce distinctive landforms, rock types, and terrains that provide a window on the chemical composition, thermal state, and history of a planet's interior. Magma is a complex, high-temperature mixture of molten silicates, suspended crystals, and dissolved gases. Magma on Mars likely ascends in a similar manner to that on Earth. It rises through the lower crust in diapiric bodies that are less dense than the surrounding material. As the magma rises, it eventually reaches regions of lower density. When the magma density matches that of the host rock, buoyancy is neutralized and the magma body stalls. At this point, it may form a magma chamber and spread out laterally into a network of dikes and sills. Subsequently, the magma may cool and solidify to form intrusive igneous bodies (plutons). Geologists estimate that about 80% of the magma generated on Earth stalls in the crust and never reaches the surface. As magma rises and cools, it undergoes many complex and dynamic compositional changes. Heavier minerals may crystallize and settle to the bottom of the magma chamber. The magma may also assimilate portions of host rock or mix with other batches of magma. These processes alter the composition of the remaining melt, so that any magma reaching the surface may be chemically quite different from its parent melt. Magmas that have been so altered are said to be "evolved" to distinguish them from "primitive" magmas that more closely resemble the composition of their mantle source. (See igneous differentiation and fractional crystallization.) More highly evolved magmas are usually felsic, that is enriched in silica, volatiles, and other light elements compared to iron- and magnesium-rich (mafic) primitive magmas. The degree and extent to which magmas evolve over time is an indication of a planet's level of internal heat and tectonic activity. The Earth's continental crust is made up of evolved granitic rocks that developed through many episodes of magmatic reprocessing. Evolved igneous rocks are much less common on cold, dead bodies such as the Moon. Mars, being intermediate in size between the Earth and the Moon, is thought to be intermediate in its level of magmatic activity. At shallower depths in the crust, the lithostatic pressure on the magma body decreases. The reduced pressure can cause gases (volatiles), such as carbon dioxide and water vapor, to exsolve from the melt into a froth of gas bubbles. The nucleation of bubbles causes a rapid expansion and cooling of the surrounding melt, producing glassy shards that may erupt explosively as tephra (also called pyroclastics). Fine-grained tephra is commonly referred to as volcanic ash. Whether a volcano erupts explosively or effusively as fluid lava depends on the composition of the melt. Felsic magmas of andesitic and rhyolitic composition tend to erupt explosively. They are very viscous (thick and sticky) and rich in dissolved gases. Mafic magmas, on the other hand, are low in volatiles and commonly erupt effusively as basaltic lava flows. However, these are only generalizations. For example, magma that comes into sudden contact with groundwater or surface water may erupt violently in steam explosions called hydromagmatic (phreatomagmatic or phreatic) eruptions. Erupting magmas may also behave differently on planets with different interior compositions, atmospheres, and gravitational fields.

2.5K
23 Nov 2022

Topic Review

Perseus, a prominent constellation in the northern celestial hemisphere, is named after the legendary Greek hero known for slaying the monstrous Gorgon Medusa. Located near the celestial equator, Perseus is recognizable for its distinctive "W" shape formed by its brightest stars and is rich in fascinating deep-sky objects.

2.5K
15 Mar 2024

Topic Review

Carina, Latin for "the keel" or "the hull," is a constellation in the southern celestial hemisphere. Representing the keel of the mythical ship Argo Navis, Carina is home to several notable celestial objects, including the second-brightest star in the night sky, Canopus. It is rich in nebulae, star clusters, and other deep-sky wonders.

2.5K
29 Feb 2024

Biography

Professor Emerita Dato' Seri Dr Mazlan binti Othman (born 11 December 1951) is a Malaysian astrophysicist whose work has pioneered Malaysia's participation in space exploration. She was her country's first astrophysicist, and helped to create a curriculum in astrophysics at the national university, as well as to build public awareness and understanding of astronomy and space issues. She was appo

2.4K
18 Nov 2022

Topic Review

Capricornus, often depicted as a sea-goat in mythology, is a zodiac constellation located in the southern celestial hemisphere. Its name is derived from the Latin words "capra," meaning goat, and "cornu," meaning horn. Capricornus is notable for containing several bright stars and is associated with the winter solstice in the Northern Hemisphere.

2.4K
29 Feb 2024

Topic Review

Lynx is a faint constellation located in the northern celestial hemisphere, bordered by Ursa Major, Auriga, Gemini, and Cancer. Named after the wild cat known for its keen vision, Lynx is notable for its lack of bright stars but contains several galaxies and deep-sky objects, making it of interest to astronomers.

2.4K
15 Mar 2024

Topic Review

Cosmogenic Activation

The cosmogenic activation of materials is the production of radioactive isotopes due to the exposure to cosmic rays. On the Earth's surface, spallation induced by cosmic neutrons is responsible of most of the activation, but other reactions and cosmic ray components must be considered too in other conditions, like if materials are flown at high altitudes or stored deep underground. Cosmogenic activation is relevant in different contexts; for example, together with primordial or anthropogenic radioactivity, it s a background source in experiments devoted to the investigation of rare event phenomena, like the direct detection of dark matter particles or the nuclear double beta decay.

2.4K
26 Oct 2020

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