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NGC 4699
NGC 4699 is an intermediate spiral galaxy located in the constellation Virgo. It is located at a distance of about 65 million light years from Earth, which, given its apparent dimensions, means that NGC 4699 is about 85,000 light years across. It was discovered by William Herschel in 1786. It is a member of the NGC 4699 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. Characteristics NGC 4699 is a Seyfert like galaxy with very weak nuclear emission. The galaxy features a bar that is 0.41 arcminutes long and a ring with diameter 1.95 arcminutes. The galaxy features a large bulge which accounts for the 11.3% of the stellar mass of the galaxy and a large disky pseudobulge, which is larger than the strong bar. The disk within the bulge features tightly wrapped spiral arms. There are many HII regions in the disk. The galaxy has an extended type-III outer disk, with low c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
New General Catalogue
The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxy, galaxies, star clusters and emission nebulae. Dreyer published two supplements to the NGC in 1895 and 1908, known as the ''Index Catalogues'' (abbreviated IC), describing a further 5,386 astronomical objects. Thousands of these objects are best known by their NGC or IC numbers, which remain in widespread use. The NGC expanded and consolidated the cataloguing work of William Herschel, William and Caroline Herschel, and John Herschel's ''General Catalogue of Nebulae and Clusters of Stars''. Objects south of the Celestial sphere, celestial equator are catalogued somewhat less thoroughly, but many were included based on observation by John Herschel or James Dunlop. The NGC contained multiple errors, but attempts to eliminate them were made by the ''Revised New Ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virgo II Groups
The Virgo II Groups, also known as the Virgo II Cloud, Virgo Southern Extension, or the Virgo S Cloud, are a series of at least 100 galactic clusters and individual galaxies stretching approximately off the southern edge of the Virgo Supercluster. It is located approximately to from the Solar System, at a right ascension of to . These clusters include: * M61 Group: ** IC 3474 ** M61 (NGC 4303) ** NGC 4255 ** NGC 4420 ** NGC 4496A ** NGC 4517A ** NGC 4527 ** NGC 4533 ** NGC 4536 ** NGC 4581 ** NGC 4599 **NGC 4632 ** PGC 40951 ** UGC 7387 ** UGC 7522 ** UGC 7612 **UGC 7780 *NGC 4030 Group: **NGC 4030 **UGC 6970 **UGC 7000 *NGC 4179 Group: **NGC 4116 **NGC 4123 **NGC 4179 **UGC 7035 *NGC 4697 Group: ** IC 3908 ** MCG-1-33-1 ** MCG-1-33-3 ** MCG-1-33-11 ** MCG-1-33-33 ** MCG-1-33-59 ** MCG-1-33-61 ** MCG-1-33-82 **NGC 4697 ** NGC 4731 ** NGC 4775 ** NGC 4941 ** NGC 4948 ** NGC 4948A ** NGC 4951 ** NGC 4958 ** UGCA 310 *NGC 4699 Group: ** MCG-2-33-15 ** MCG-2-33-47 ** MCG-1-33-60 * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zwicky Transient Facility
The Zwicky Transient Facility (ZTF, List of observatory codes, obs. code: IAU code#I41, I41) is a wide-field sky astronomical survey using a new camera attached to the Samuel Oschin Telescope at Palomar Observatory in San Diego County, California, United States. Commissioned in 2018, it supersedes the (Intermediate) Palomar Transient Factory (2009–2017) that used the same observatory code. It is named after the Swiss people, Swiss astronomer Fritz Zwicky. Description Observing in visible and infrared wavelengths, the Zwicky Transient Facility is designed to detect Transient astronomical event, transient objects that rapidly change in brightness, for example supernovae, gamma ray bursts, and collision between two neutron stars, and moving objects like comets and asteroids. The new camera is made of 16 Charge-coupled device, CCDs of 6144×6160 pixels each, enabling each exposure to cover an area of 47 square degrees. The Zwicky Transient Facility is designed to image the enti ... [...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] |
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] |
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] |
Edwin Hubble
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology. Hubble proved that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually Galaxy, galaxies beyond the Milky Way. He used the strong direct period-luminosity relation, relationship between a classical Cepheid variable's luminosity and periodic function, pulsation period (discovered in 1908 by Henrietta Swan Leavitt) for scaling cosmic distance ladder, galactic and extragalactic distances. Hubble confirmed in 1929 that the recessional velocity of a galaxy increases with its distance from Earth, a behavior that became known as Hubble's law, although it had been proposed two years earlier by Georges Lemaître. The Hubble law implies that the universe is expanding. A decade before, the American astronomer Vesto Slipher had provided the fi ... [...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] |
Disc (galaxy)
A galactic disc (or galactic disk) is a component of disc galaxies, such as spiral galaxies like the Milky Way and lenticular galaxies. Galactic discs consist of a stellar component (composed of most of the galaxy's stars) and a gaseous component (mostly composed of cool gas and dust). The stellar population of galactic discs tend to exhibit very little random motion with most of its stars undergoing nearly circular orbits about the galactic center. Discs can be fairly thin because the disc material's motion lies predominantly on the plane of the disc (very little vertical motion). The Milky Way's disc, for example, is approximately 1 kly thick, but thickness can vary for discs in other galaxies. Stellar component Exponential surface brightness profiles Galactic discs have surface brightness profiles that very closely follow exponential functions in both the radial and vertical directions. Radial profile The surface brightness radial profile of the galactic disc of a t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HII Region
An H II region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds of light years, and density from a few to about a million particles per cubic centimetre. The Orion Nebula, now known to be an H II region, was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered. The regions may be of any shape because the distribution of the stars and gas inside them is irregular. The short-lived blue stars created in these regions emit copious amounts of ultraviolet light that ionize the surrounding gas. H II regions—sometimes several hundred light-years across—are often associated with giant molecular clouds. They often appear clumpy and filamentary, sometimes showing intricate shapes such as the Horsehead Nebula. H II regions may give birth to thousands of stars ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bulge (astronomy)
In astronomy, a galactic bulge (or simply bulge) is a tightly packed group of stars within a larger star formation. The term almost exclusively refers to the group of stars found near the Galaxy#Center, center of most spiral galaxy, spiral galaxies (see ''galactic spheroid''). Bulges were historically thought to be elliptical galaxies that happened to have a Galactic disc, disk of stars around them, but high-resolution images using the Hubble Space Telescope have revealed that many bulges lie at the heart of a spiral galaxy. It is now thought that there are at least two types of bulges: bulges that are like ellipticals and bulges that are like spiral galaxies. Classical bulges Bulges that have properties similar to those of elliptical galaxies are often called "classical bulges" due to their similarity to the historic view of bulges. These bulges are composed primarily of stars that are older, Population II, Population II stars, and hence have a reddish hue (see stellar evolu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barred Spiral Galaxy
A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about two thirds of all spiral galaxies in the local universe, and generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well. The Milky Way Galaxy, where the Solar System is located, is classified as a barred spiral galaxy. Edwin Hubble classified spiral galaxies of this type as "SB" (spiral, barred) in his Hubble sequence and arranged them into sub-categories based on how open the arms of the spiral are. SBa types feature tightly bound arms, while SBc types are at the other extreme and have loosely bound arms. SBb-type galaxies lie in between the two. SB0 is a barred lenticular galaxy. A new type, SBm, was subsequently created to describe somewhat Barred irregular galaxy, irregular barred spirals, such as the Magellanic Clouds, which were once classified as irregular galaxies, but have since been found t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
