|
Millennium Star Atlas
The ''Millennium Star Atlas'' was constructed as a collaboration between a team at '' Sky & Telescope'' led by Roger Sinnott, and the European Space Agency's Hipparcos project, led by Michael Perryman. This 1997 work was the first sky atlas to include the ''Hipparcos'' and ''Tycho Catalogue'' data, extending earlier undertakings in terms of completeness and uniformity to a magnitude limit of around 10–11 magnitude. It appeared as a stand-alone publication, and as three volumes of the 17-volume '' Hipparcos Catalogue''. The 1548 charts include one million stars from the Hipparcos and Tycho-1 Catalogues, three times as many as in any previous all-sky atlas; more than 8000 galaxies with their orientation; outlines of many bright and dark nebulae; the location of many open and globular clusters; and some 250 of the brightest quasar A quasar is an extremely Luminosity, luminous active galactic nucleus (AGN). It is pronounced , and sometimes known as a quasi-stellar object, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sky & Telescope
''Sky & Telescope'' (''S&T'') is a monthly American magazine covering all aspects of amateur astronomy, including the following: *current events in astronomy and space exploration; *events in the amateur astronomy community; *reviews of astronomical equipment, books, and computer software; *amateur telescope making; and *astrophotography. The articles are intended for the informed lay reader and include detailed discussions of current discoveries, frequently by participating scientists. The magazine is illustrated in full color, with both amateur and professional photography of celestial sights, as well as tables and charts of upcoming celestial events. History ''Sky & Telescope'' was founded by Charles A Federer and his wife Helen Spence Federer and began publication at Harvard College Observatory in November 1941, as a result of the merger of the separate magazines, '' The Sky'' and '' The Telescope''. In 2005, Sky Publishing Corporation was acquired by New Track Media, a portfo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Nebula
A dark nebula or absorption nebula is a type of interstellar cloud, particularly molecular clouds, that is so dense that it obscures the visible wavelengths of light from objects behind it, such as background stars and emission or reflection nebulae. The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of molecular clouds. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called Bok globules. Like other interstellar dust or material, things it obscures are only visible using radio waves in radio astronomy or infrared in infrared astronomy. Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, C18O (CO with oxygen as the 18O isotope), CS, NH3 (ammonia), H2CO (formaldehyde), c-C3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrometry
Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. History The history of astrometry is linked to the history of star catalogues, which gave astronomers reference points for objects in the sky so they could track their movements. This can be dated back to Hipparchus, who around 190 BC used the catalogue of his predecessors Timocharis and Aristillus to discover Earth's precession. In doing so, he also developed the brightness scale still in use today. Hipparchus compiled a catalogue with at least 850 stars and their positions. Hipparchus's successor, Ptolemy, included a catalogue of 1,022 stars in his work the '' Almagest'', giving their location, coordinates, and brightness. In the 10th century, Abd al-Rahman al-Sufi carried out observations on the stars and described their positions, ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UBV Photometric System
The UBV photometric system (from ''Ultraviolet, Blue, Visual''), also called the Johnson system (or Johnson-Morgan system), is a photometric system usually employed for classifying stars according to their colors. It was the first standardized photometric system. The apparent magnitudes of stars in the system are often used to determine the color indices B-V and U-B, the difference between the B and V magnitudes and the U and B magnitudes respectively. The choice of colors on the blue end of the spectrum was assisted by the bias that photographic film has for those colors. It was introduced in the 1950s by American astronomers Harold Lester Johnson and William Wilson Morgan. A telescope and the telescope at McDonald Observatory were used to define the system. The filters are selected so that the mean wavelengths of response functions (at which magnitudes are measured to mean precision) are 364 nm for U, 442 nm for B, 540 nm for V. Zero points were calibrate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quasar
A quasar is an extremely Luminosity, luminous active galactic nucleus (AGN). It is pronounced , and sometimes known as a quasi-stellar object, abbreviated QSO. This emission from a galaxy nucleus is powered by a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Gas in the disc falling towards the black hole heats up because of friction and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosity, luminosities thousands of times greater than that of a galaxy such as the Milky Way. Usually, quasars are categorized as a subclass of the more general category of AGN. The redshifts of quasars are of Expansion of the universe, cosmological origin. The term originated as a Contraction (grammar), contraction of "quasi-stellar ''[star-like]'' radio source"—because quasars were first identified during the 1950s as sour ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Globular Cluster
A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of member stars. Their name is derived from Latin (small sphere). Globular clusters are occasionally known simply as "globulars". Although one globular cluster, Omega Centauri, was observed in antiquity and long thought to be a star, recognition of the clusters' true nature came with the advent of telescopes in the 17th century. In early telescopic observations globular clusters appeared as fuzzy blobs, leading French astronomer Charles Messier to include many of them in his catalog of astronomical objects that he thought could be mistaken for comets. Using larger telescopes, 18th-century astronomers recognized that globular clusters are groups of many individual stars. Early in the 20th century the distribution of globular clusters in the sky w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Cluster
An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and many more are thought to exist. They are loosely bound by mutual gravity, gravitational attraction and become disrupted by close encounters with other clusters and clouds of gas as they orbit the Galactic Center. This can result in a migration to the main body of the galaxy and a loss of cluster members through internal close encounters. Open clusters generally survive for a few hundred million years, with the most massive ones surviving for a few billion years. In contrast, the more massive globular clusters of stars exert a stronger gravitational attraction on their members, and can survive for longer. Open clusters have been found only in spiral galaxy, spiral and irregular galaxy, irregular galaxies, in which active star formation is o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bright Nebula
A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ 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 will 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 sur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roger Sinnott
Roger is a given name, usually masculine, and a surname. The given name is derived from the Old French personal names ' and '. These names are of Germanic origin, derived from the elements ', ''χrōþi'' ("fame", "renown", "honour") and ', ' ("spear", "lance") (Hrōþigēraz). The name was introduced into England by the Normans. In Normandy, the Frankish name had been reinforced by the Old Norse cognate '. The name introduced into England replaced the Old English cognate '. ''Roger'' became a very common given name during the Middle Ages. A variant form of the given name ''Roger'' that is closer to the name's origin is ''Rodger''. Slang and other uses Roger is also a short version of the term "Jolly Roger", which refers to a black flag with a white skull and crossbones, formerly used by sea pirates since as early as 1723. From up to , Roger was slang for the word "penis". In ''Under Milk Wood'', Dylan Thomas writes "jolly, rodgered" suggesting both the sexual double entend ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galaxy
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a hundred million stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies. Galaxies are categorized according to their visual morphology as elliptical, spiral, or irregular. Many are thought to have supermassive black holes at their centers. The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times greater than the Sun. As o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sky, night, but their immense distances from Earth make them appear as fixed stars, fixed points of light. The most prominent stars have been categorised into constellations and asterism (astronomy), asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated to stars. Only about 4,000 of these stars are visible to the naked eye, all within the Milky Way galaxy. A star's life star formation, begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Its stellar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
