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NGC 3198
NGC 3198, also known as Herschel 146 is a barred spiral galaxy in the constellation Ursa Major. It was discovered by William Herschel on 15 January 1788. NGC 3198 is located in the Leo Spur, which is part of the Virgo Supercluster, and is approximately 47 million light years away. NGC 3198 was one of 18 galaxies targeted by the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale, which aimed to calibrate various secondary distance indicators and determine the Hubble constant to an accuracy of 10%. The type and orientation of NGC 3198 made it suitable for these measurements. The Wide Field and Planetary Camera 2 (WFPC2) of the HST was used to measure the magnitudes of 52 Cepheid variables, and the resulting distance modulus corresponded to a distance of 14.5 Mpc (47 million light years). Observations made with the Westerbork Synthesis Radio Telescope detected for the first time the presence of extraplanar gas. The extraplanar gas makes up approxim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nicholas U
Nicholas is a male name, the Anglophone version of an ancient Greek name in use since antiquity, and cognate with the modern Greek , . It originally derived from a combination of two Greek words meaning 'victory' and 'people'. In turn, the name means "victory of the people." The name has been widely used in countries with significant Christian populations, owing in part to the veneration of Saint Nicholas, which became increasingly prominent in Western Europe from the 11th century. Revered as a saint in many Christian denominations, the Eastern Orthodox, Catholic, and Anglican Churches all celebrate Saint Nicholas Day on December 6. In maritime regions throughout Europe, the name and its derivatives have been especially popular, as St Nicholas is considered the protector saint of seafarers. This remains particularly so in Greece, where St Nicholas is the patron saint of the Hellenic Navy. Origins The name derives from the . It is understood to mean 'victory of the people' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apparent Magnitude
Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), extinction of the object's light caused by interstellar dust along the sightline, line of sight to the observer. Unless stated otherwise, the word ''magnitude'' in astronomy usually refers to a celestial object's apparent magnitude. The magnitude scale likely dates to before the ancient Ancient Greek astronomy#Astronomy in the Greco-Roman and Late Antique eras, Roman astronomer Ptolemy, Claudius Ptolemy, whose Star catalogue, star catalog popularized the system by listing stars from First-magnitude star, 1st magnitude (brightest) to 6th magnitude (dimmest). The modern scale was mathematically defined to closely match this historical system by Norman Robert Pogson, Norman Pogson in 1856. The scale is reverse logarithmic scale, logarithmic: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type II Supernova
A Type II supernova or SNII (plural: ''supernovae'') results from the rapid collapse and violent explosion of a massive star. A star must have at least eight times, but no more than 40 to 50 times, the mass of the Sun () to undergo this type of explosion. Type II supernovae are distinguished from other types of supernovae by the presence of hydrogen in their spectra. They are usually observed in the spiral arms of galaxies and in H II regions, but not in elliptical galaxies; those are generally composed of older, low-mass stars, with few of the young, very massive stars necessary to cause a supernova. Stars generate energy by the nuclear fusion of elements. Unlike the Sun, massive stars possess the mass needed to fuse elements that have an atomic mass greater than hydrogen and helium, albeit at increasingly higher temperatures and pressures, causing correspondingly shorter stellar life spans. The degeneracy pressure of electrons and the energy generated by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Ib And Ic Supernovae
Type Ib and Type Ic supernovae are categories of supernovae that are caused by the stellar core collapse of massive stars. These stars have shed or been stripped of their outer envelope of hydrogen, and, when compared to the spectrum of Type Ia supernovae, they lack the absorption line of silicon. Compared to Type Ib, Type Ic supernovae are hypothesized to have lost more of their initial envelope, including most of their helium. Spectra When a supernova is observed, it can be categorized in the Minkowski– Zwicky supernova classification scheme based upon the absorption lines that appear in its spectrum. A supernova is first categorized as either a Type I or Type II, then subcategorized based on more specific traits. Supernovae belonging to the general category Type I lack hydrogen lines in their spectra; in contrast to Type II supernovae which do display lines of hydrogen. The Type I category is subdivided into Type Ia, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paul Wild (Swiss Astronomer)
Paul Wild (; 5 October 1925 – 2 July 2014) was a Swiss astronomer and director of the Astronomical Institute of the University of Bern, who discovered numerous comets, asteroids and supernovae. Biography Wild was born on 5 October 1925 in the village of Wädenswil near Zürich, Switzerland. From 1944 through 1950, he studied mathematics and physics at the ETH Zurich. Thereafter, he worked at the California Institute of Technology where he researched galaxies and supernovas under the leadership of countryman Fritz Zwicky from 1951 through 1955. At the Zimmerwald Observatory, near Bern, Wild made his first cometary discovery C/1957 U1 (1957 IX) on 2 October 1957. The parabolic comet was later named "Latyshev-Wild– Burnham". Professor Wild became director of the Astronomical Institute of the University of Bern in 1980, and remained in this position until 1991. He died on 2 July 2014 at the age of 88 in Bern. Discoveries During countless nights Wild observed the ski ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Astronomical Union
The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and development through global cooperation. It was founded on 28 July 1919 in Brussels, Belgium and is based in Paris, France. The IAU is composed of individual members, who include both professional astronomers and junior scientists, and national members, such as professional associations, national societies, or academic institutions. Individual members are organised into divisions, committees, and working groups centered on particular subdisciplines, subjects, or initiatives. the Union had 85 national members and 12,734 individual members, spanning 90 countries and territories. Among the key activities of the IAU is serving as a forum for scientific conferences. It sponsors nine annual symposia and holds a triannual General Assembly that sets policy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Ia Supernova
A Type Ia supernova (read: "type one-A") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white dwarf. Physically, carbon–oxygen white dwarfs with a low rate of rotation are limited to below 1.44 solar masses (). Beyond this "Chandrasekhar limit, critical mass", they reignite and in some cases trigger a supernova explosion; this critical mass is often referred to as the Chandrasekhar mass, but is marginally different from the absolute Chandrasekhar limit, where electron degeneracy pressure is unable to prevent catastrophic collapse. If a white dwarf gradually accretes mass from a binary companion, or merges with a second white dwarf, the general hypothesis is that a white dwarf's core will reach the ignition temperature for Carbon burning process, carbon fusion as it approaches the Chandrasekhar mass. Within a few seconds of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supernova
A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion. The original object, called the ''progenitor'', either collapses to a neutron star or black hole, or is completely destroyed to form a diffuse nebula. The peak optical luminosity of a supernova can be comparable to that of an entire galaxy before fading over several weeks or months. The last supernova directly observed in the Milky Way was Kepler's Supernova in 1604, appearing not long after Tycho's Supernova in 1572, both of which were visible to the naked eye. The supernova remnant, remnants of more recent supernovae have been found, and observations of supernovae in other galaxies suggest they occur in the Milky Way on average about three times every century. A supernova in the Milky Way would almost certainly be observable through mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Hydrogen
A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral hydrogen atom contains a single positively charged proton in the nucleus, and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constitutes about 75% of the baryonic mass of the universe. In everyday life on Earth, isolated hydrogen atoms (called "atomic hydrogen") are extremely rare. Instead, a hydrogen atom tends to combine with other atoms in compounds, or with another hydrogen atom to form ordinary (diatomic) hydrogen gas, H2. "Atomic hydrogen" and "hydrogen atom" in ordinary English use have overlapping, yet distinct, meanings. For example, a water molecule contains two hydrogen atoms, but does not contain atomic hydrogen (which would refer to isolated hydrogen atoms). Atomic spectroscopy shows that there is a discrete infinite set of states in which a hydrogen (or any) atom can exist, contrary to the predictions of classical physics. At ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomy & Astrophysics
''Astronomy & Astrophysics (A&A)'' is a monthly peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics. It is operated by an editorial team under the supervision of a board of directors representing 27 sponsoring countries plus a representative of the European Southern Observatory. The journal is published by EDP Sciences and the current editors-in-chief are Thierry Forveille and João Alves. History Origins ''Astronomy & Astrophysics'' was created as an answer to the publishing situation found in Europe in the 1960s. At that time, multiple journals were being published in several countries around the continent. These journals usually had a limited number of subscribers, and articles were written in languages other than English. They were less widely read than American and British journals and the research they reported had therefore less impact in the community. Starting in 1963, conversations between astronomers from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extraplanar Gas
Extraplanar gas is cold atomic hydrogen which has been discovered slowly rotating around some spiral galaxies and located well outside their thin disk regions. It was discovered by using radio telescopes to observe the distribution of atomic hydrogen around galaxy disks. Galaxies which have shown evidence of extraplanar gas include NGC 891, NGC 2403, UGC 7321, NGC 4559 and NGC 3198. Possible explanations for the presence of this gas include ionised gas being swept up by stellar winds and supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ... explosions and, upon cooling, falling back into the galactic plane and the accretion of intergalactic primordial gas. References {{Reflist Intergalactic media Radio astronomy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Westerbork Synthesis Radio Telescope
The Westerbork Synthesis Radio Telescope (WSRT) is an aperture synthesis interferometer built on the site of the former World War II Nazi detention and transit Westerbork transit camp, camp Westerbork, north of the village of Westerbork (village), Westerbork, Midden-Drenthe, in the northeastern Netherlands. Overview The WSRT comprises fourteen radio telescopes deployed in a linear array arranged on a East-West line, of which 10 are in a fixed equidistant position, 2 are nearby on a rail track, and 2 are located eastwards on another rail track. It has a similar arrangement to other radio telescopes such as the One-Mile Telescope, Australia Telescope Compact Array and the Ryle Telescope. Its Equatorial mount is what sets it apart from most other radio telescopes, most of which have an Altazimuth mount. This makes it specifically useful for specific types of science, like polarized emission research as the detectors maintain a constant orientation on the sky during an observat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
