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ω Centauri
Omega Centauri (ω Cen, NGC 5139, or Caldwell 80) is a globular cluster in the constellation of Centaurus that was first identified as a non-stellar object by Edmond Halley in 1677. Located at a distance of , it is the largest known globular cluster in the Milky Way at a diameter of roughly 150 light-years. It is estimated to contain approximately 10 million stars, with a total mass of 4 million solar masses, making it the most massive known globular cluster in the Milky Way. Omega Centauri is very different from most other galactic globular clusters to the extent that it is thought to have originated as the core remnant of a disrupted dwarf galaxy. Observation history Around 150 AD, Greco-Roman writer and astronomer Ptolemy catalogued this object in his ''Almagest'' as a star on the centaur's back, "Quae est in principio scapulae". German cartographer Johann Bayer used Ptolemy's data to designate this object "Omega Centauri" with his 1603 publication of ''Uranometria''. Using a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Omega Centauri Stars
Omega (, ; uppercase Ω, lowercase ω; Ancient Greek ὦ, later ὦ μέγα, Modern Greek ωμέγα) is the twenty-fourth and last letter in the Greek alphabet. In the Greek numeric system/isopsephy (gematria), it has a value of 800. The word literally means "great O" (''o mega'', mega meaning "great"), as opposed to omicron, which means "little O" (''o mikron'', mikron meaning "little"). In phonetic terms, the Ancient Greek Ω represented a long open-mid back rounded vowel , comparable to the "aw" of the English word ''raw'' in dialects without the cot–caught merger, in contrast to omicron, which represented the close-mid back rounded vowel , and the digraph ''ου'', which represented the long close-mid back rounded vowel . In Modern Greek, both omega and omicron represent the mid back rounded vowel or . The letter omega is transliterated into a Latin-script alphabet as ''ō'' or simply ''o''. As the final letter in the Greek alphabet, omega is often used to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Uranometria
is a star atlas produced by Johann Bayer. It was published in Augsburg in 1603 by Christoph Mang (''Christophorus Mangus'') under the full title (from Latin: ''Uranometria, containing charts of all the constellations, drawn by a new method and engraved on copper plates''). The word "uranometria", , literally translates to "measuring the heavens". It was the first atlas to cover the entire celestial sphere. Charts ''Uranometria'' contains 51 star charts, engraved on copper plates by Alexander Mair ( 1562–1617). The first 48 charts illustrate each of the 48 Ptolemaic constellations. The 49th chart introduces 12 new constellations in the deep southern sky, which was unknown to Ptolemy. The final two charts are planispheres labeled "''Synopsis coeli superioris borea''" and "''Synopsis coeli inferioris austrina''", or (roughly), "Overview of the northern celestial hemisphere" and "Overview of the southern celestial hemisphere". Each plate includes a grid for accurately deter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Population II
In 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926. Baade observed that bluer stars were strongly associated with the spiral arms, and yellow stars dominated near the central galactic bulge and within globular star clusters. Two main divisions were deemed ''populationI'' and ''populationII stars'', with another newer, hypothetical division called ''populationIII'' added in 1978. Among the population types, significant differences were found with their individual observed stellar spectra. These were later shown to be very important and were possibly related to star formation, observed kinematics, stellar age, and even galaxy evolution in both spiral and elliptical galaxies. These three simple population classes usefully divided stars by their chemical composition, or '' metallicity''. In astrophysics n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Andromeda Galaxy
The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224. Andromeda has a Galaxy#Isophotal diameter, D25 isophotal diameter of about and is approximately from Earth. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after Andromeda (mythology), the princess who was the wife of Perseus in Greek mythology. The virial mass of the Andromeda Galaxy is of the same order of magnitude as that of the Milky Way, at . The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought that the Andromeda Galaxy was more massive than the Milky Way by a margin of some 25% to 50%. However, this has been called into question by early-21st-century studies indicating a possibly lower mass for the Andromeda Galaxy and a higher mass for the Milky Way. The Androm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Mayall II
Mayall II, also known as NGC-224-G1, SKHB 1, GSC 2788:2139, HBK 0-1, M31GC J003247+393440 or Andromeda's Cluster, is a globular cluster orbiting M31, the Andromeda Galaxy. It is located from the Andromeda Galaxy's galactic core, and is the brightest (by absolute magnitude) globular cluster in the Local Group, with an absolute visual magnitude of −10.94 and the luminosity of 2 million Suns. It has an apparent magnitude of 13.81 in V band. Mayall II is considered to have twice the mass of Omega Centauri, and may contain a central, intermediate-mass (~ 2 M⊙) black hole. It was first identified as a possible globular cluster by American astronomers Nicholas Mayall and Olin J. Eggen in 1953 using a Palomar Schmidt plate exposed in 1948. Because of the widespread distribution of metallicity, indicating multiple star generations and a large stellar creation period, many contend that it is not a true globular cluster, but is actually the galactic core that remains of a dwa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Local Group
The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It has a total diameter of roughly , and a total mass of the order of . It consists of two collections of galaxies in a " dumbbell" shape; the Milky Way and its satellites form one lobe, and the Andromeda Galaxy and its satellites constitute the other. The two collections are separated by about and are moving toward one another with a velocity of . The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster. The exact number of galaxies in the Local Group is unknown as some are occluded by the Milky Way; however, at least 80 members are known, most of which are dwarf galaxies. The two largest members, the Andromeda and the Milky Way galaxies, are both spiral galaxies with masses of about solar masses each. Each has its own system of satellite galaxies: * The Andromeda Galaxy's satellite system consists of Messier 32 (M32), Messier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Moon
The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar day) that is synchronized to its orbital period (Lunar month#Synodic month, lunar month) of 29.5 Earth days. This is the product of Earth's gravitation having tidal forces, tidally pulled on the Moon until one part of it stopped rotating away from the near side of the Moon, near side, making always the same lunar surface face Earth. Conversley, the gravitational pull of the Moon, on Earth, is the main driver of Earth's tides. In geophysical definition of planet, geophysical terms, the Moon is a planetary-mass object or satellite planet. Its mass is 1.2% that of the Earth, and its diameter is , roughly one-quarter of Earth's (about as wide as the contiguous United States). Within the Solar System, it is the List of Solar System objects by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering Water distribution on Earth, 70.8% of Earth's crust. The remaining 29.2% of Earth's crust is land, most of which is located in the form of continental landmasses within Earth's land hemisphere. Most of Earth's land is at least somewhat humid and covered by vegetation, while large Ice sheet, sheets of ice at Polar regions of Earth, Earth's polar polar desert, deserts retain more water than Earth's groundwater, lakes, rivers, and Water vapor#In Earth's atmosphere, atmospheric water combined. Earth's crust consists of slowly moving tectonic plates, which interact to produce mountain ranges, volcanoes, and earthquakes. Earth's outer core, Earth has a liquid outer core that generates a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
James Dunlop
James Dunlop FRSE (31 October 1793 – 22 September 1848) was a Scottish astronomer, noted for his work in Australia. He was employed by Sir Thomas Brisbane to work as astronomer's assistant at his private observatory, once located at Paramatta (now named Parramatta), New South Wales, about west of Sydney during the 1820s and 1830s. Dunlop was mostly a visual observer, doing stellar astrometry work for Brisbane, and after its completion, then independently discovered and catalogued many new telescopic southern double stars and deep-sky objects. He later became the Superintendent of Paramatta Observatory when it was finally sold to the New South Wales Government. Early life James Dunlop was born in Dalry, Ayrshire, Scotland, the son of John Dunlop, a weaver, and his wife Janet, ''née'' Boyle. Dunlop was educated at a primary school in Dalry and went to work at a thread factory in Beith when he was 14. He also attended a night-school in Beith kept by a man named Gardiner ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Guillaume Bigourdan
Camille Guillaume Bigourdan (; 6 April 1851 – 28 February 1932) was a French astronomer. Personal life Bigourdan was born at Sistels, Tarn-et-Garonne to Pierre Bigourdan and Jeanne Carrière. When his teachers and local curate recognised his intelligence, he was transferred to a local boarding school in Valence d’Agen, where he excelled. In 1870, he received his Baccalauréat with mention of "Assez Bien". He married Marie Mélanie Sophie Mouchez, the eldest daughter of Admiral Amédée Mouchez. Together, the two had nine children. The entire family, including the Mouchez cousins, would frequently vacation in Sistels until the outbreak of the First World War, after which Bigourdan would vacation alone. During these vacations, he would farm his land and visit former classmates. He was fluent in Occitan, and spoke it when in Sistels. Academic and scientific career Bigourdan studied at the University of Toulouse from 1870, where he received a physics degree in 1874 and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Nebula
A nebula (; or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral, or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regions, such as in the Pillars of Creation in the Eagle Nebula. In these regions, the formations of gas, dust, and other materials "clump" together to form denser regions, which attract further matter and eventually become dense enough to form stars. The remaining material is then thought to form planets and other planetary system objects. Most nebulae are of vast size; some are hundreds of light-years in diameter. A nebula that is visible to the human eye from Earth would appear larger, but no brighter, from close by. The Orion Nebula, the brightest nebula in the sky and occupying an area twice the angular diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers. Although denser than the space surrounding them, most nebulae are far less dens ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
