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NGC 45
NGC 45 is a low surface brightness spiral galaxy in the equatorial constellation of Cetus. It was discovered on 11 November 1835 by the English astronomer John Herschel. The galaxy is located at a distance of 22 million light years and is receding with a heliocentric radial velocity of . It is located in the vicinity of the Sculptor Group, but is most likely a background galaxy. The morphological class of NGC 45 is SA(s)dm, indicating this is a spiral galaxy with no prominent inner bar (SA) or ring (s) feature. There is no central bulge to speak of. The galactic plane is inclined at an angle of to the line of sight from the Earth, with the major axis of the elliptical profile being aligned along a position angle of . Star formation is proceeding at a modest rate of ·yr−1. Unlike the Milky Way, NGC 45 has no clearly defined spiral arms, and its center bar nucleus is also very small and distorted. NGC 45 thus does not have a galactic habitable zone. For the Milk ...
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DECam
The Dark Energy Survey (DES) is an astronomical survey designed to constrain the properties of dark energy. It uses images taken in the near-ultraviolet, visible, and near-infrared to measure the expansion of the universe using Type Ia supernovae, baryon acoustic oscillations, the number of galaxy clusters, and weak gravitational lensing. The collaboration is composed of research institutions and universities from the United States,DES Collaboration Page
DES Collaborators.
Australia, Brazil,DES-Brazil
, DES-Brazil Consortium.
the United Kingdom, Germany, Spain, and Switzerland. The collaboration is divided into several scientific working groups. The director of DES is
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Spiral Arm
Spiral arms are a defining feature of spiral galaxies. They manifest as spiral-shaped regions of enhanced brightness within the galactic disc. Typically, spiral galaxies exhibit two or more spiral arms. The collective configuration of these arms is referred to as the spiral pattern or spiral structure of the galaxy. The appearance of spiral sleeves is quite diverse. Grand design spiral galaxy, Grand design spiral galaxies exhibit a symmetrical and distinct pattern, comprising two spiral arms that extend throughout the galaxy. In contrast, the spiral structure of flocculent galaxies comprises numerous small fragments of arms that are not connected to each other. The appearance of spiral arms varies across the electromagnetic spectrum. In addition to increased brightness, spiral arms are characterised by an increased concentration of interstellar medium, interstellar gas and dust, bright stars and star clusters, active starburst region, starburst, a bluer colour, and an enhanced mag ...
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List Of NGC Objects (1–1000)
This is a list of NGC objects 1–1000 from the New General Catalogue (NGC). The astronomical catalogue is composed mainly of star clusters, nebulae, and galaxies. Other objects in the catalogue can be found in the other subpages of the list of NGC objects. The constellation information in these tables is from ''The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer'', which was accessed using the VizieR Service. Galaxy morphological types and objects that are members of the Small Magellanic Cloud are identified using the ''NASA/IPAC Extragalactic Database''. The other data of these tables are from the SIMBAD Astronomical Database unless otherwise stated. 1–100 101–200 201–300 301–400 401–500 501–600 601–700 701–800 801–900 901–1000 See also * Lists of astronomical objects This is a list of lists, grouped by type of astronomical object. Solar System * List of Sol ...
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Hubble Space Telescope
The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most versatile, renowned as a vital research tool and as a public relations boon for astronomy. The Hubble Space Telescope is named after astronomer Edwin Hubble and is one of NASA's Great Observatories program, Great Observatories. The Space Telescope Science Institute (STScI) selects Hubble's targets and processes the resulting data, while the Goddard Space Flight Center (GSFC) controls the spacecraft. Hubble features a mirror, and its five main instruments observe in the ultraviolet, visible spectrum, visible, and near-infrared regions of the electromagnetic spectrum. Hubble's orbit outside the distortion of atmosphere of Earth, Earth's atmosphere allows it to capture extremely high-resolution images with substantially lower background lig ...
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Ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs, Cherenkov radiation, and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. The photons of ultraviolet have greater energy than those of visible light, from about 3.1 to 12  electron volts, around the minimum energy required to ionize atoms. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack sufficient energy, it can induce chemical reactions and cause many substances to glow or fluoresce. Many practical applications, including chemical and biological effects, are derived from the way that UV radiation can interact with organic molecules. The ...
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GALEX
Galaxy Evolution Explorer (GALEX or Explorer 83 or SMEX-7) was a NASA orbiting space telescope designed to observe the universe in ultraviolet wavelengths to measure the history of star formation in the universe. In addition to paving the way for future ultraviolet missions, the space telescope allowed astronomers to uncover mysteries about the early universe and how it evolved, as well as better characterize phenomena like black holes and dark matter. The mission was extended three times over a period of 10 years before it was decommissioned in June 2013. GALEX was launched on 28 April 2003 and decommissioned in June 2013. Spacecraft The spacecraft was three-axis stabilized, with power coming from four fixed solar panels. The satellite bus is from Orbital Sciences Corporation based on OrbView 4. The telescope was a Modified Ritchey–Chrétien with a rotating grism. GALEX used the first ever UV light dichroic beam-splitter flown in space to direct photons to the Near ...
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Luminous Blue Variable
Luminous blue variables (LBVs) are rare, massive, evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Large Magellanic Cloud. Discovery and history The LBV stars P Cygni and Eta Carinae, η Carinae have been known as unusual variables since the 17th century, but their true nature was not fully understood until late in the 20th century. In 1922 John Charles Duncan published the first three variable stars ever detected in an external galaxy, variables 1, 2, and 3, in the Triangulum Galaxy (M33). These were followed up by Edwin Hubble with three more in 1926: A, B, and C in M33. Then in 1929 Hubble added a list of variables detected in Messier 31, M31. Of these, Var A, Var B, Var C, and Var 2 in M33 and Var 19 in M31 were followed up with a detailed study by Hubble and Allan Sandage in 1953. Var 1 in M33 was excluded as being too faint a ...
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Yellow Supergiant
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 hotter and smaller than red supergiants; naked eye examples include Polaris, Alpha Leporis, Alpha Persei, Delta Canis Majoris and Iota¹ Scorpii. Many of them are variable stars, mostly pulsating Cepheids such as δ Cephei itself. Spectrum Yellow supergiants generally have spectral types of F and G, although sometimes late A or early K stars are included. These spectral types are characterised by hydrogen lines that are very strong in class A, weakening through F and G until they are very weak or absent in class K. Calcium H and K lines are present in late A spectra, but stronger in class F, and strongest in class G, before weakening again in cooler stars. Lines of ionised metals are strong in class A, weaker in class F and G, ...
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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 ...
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Luminous Red Nova
A luminous red nova (abbr. ''LRN'', pl. ''luminous red novae'', pl.abbr. ''LRNe'') is a stellar explosion thought to be caused by the merging of two stars. They are characterised by a distinct red colour, and a light curve that fades slowly with resurgent brightness in the infrared. Luminous red novae are not related to standard novae, which are explosions that occur on the surface of white dwarf stars. Discovery A small number of objects exhibiting the characteristics of luminous red novae have been observed over the last 30 years or so. The red star M31 RV in the Andromeda Galaxy flared brightly during 1988 and may have been a luminous red nova. In 1994, V4332 Sagittarii, a star in the Milky Way galaxy, flared similarly, and in 2002, V838 Monocerotis followed suit and was studied quite closely. The first confirmed luminous red nova was the object M85 OT2006-1, in the galaxy Messier 85. It was first observed during the Lick Observatory Supernova Search, and subsequently i ...
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Time-domain Astronomy
Time-domain astronomy is the study of how astronomical objects change with time. Said to have begun with Galileo's '' Letters on Sunspots'', the field has now naturally expanded to encompass variable objects beyond the Solar System. Temporal variation may originate from movement of the source, or changes in the object itself. Common targets include novae, supernovae, pulsating stars, flare stars, blazars and active galactic nuclei. Optical time domain surveys include OGLE, HAT-South, PanSTARRS, SkyMapper, ASAS, WASP, CRTS, GOTO, and the forthcoming LSST at the Vera C. Rubin Observatory. Time-domain astronomy studies transient astronomical events ("''transients''"), which include various types of variable stars, including periodic, quasi-periodic, high proper motion stars, and lifecycle events (supernovae, kilonovae) or other changes in behavior or type. Non-stellar transients include asteroids, planetary transits and comets. Transients characterize astronomical obje ...
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Kiloparsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and is defined as the distance at which 1 AU subtends an angle of one arcsecond ( of a degree). The nearest star, Proxima Centauri, is about from the Sun: from that distance, the gap between the Earth and the Sun spans slightly less than one arcsecond. Most stars visible to the naked eye are within a few hundred parsecs of the Sun, with the most distant at a few thousand parsecs, and the Andromeda Galaxy at over 700,000 parsecs. The word ''parsec'' is a shortened form of ''a distance corresponding to a parallax of one second'', coined by the British astronomer Herbert Hall Turner in 1913. The unit was introduced to simplify the calculation of astronomical distances from raw observational data. Partly for this reason, it is the unit ...
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