NGC 7007 is a lenticular galaxy around 130 million light-years away from Earth in the constellation Indus. NGC 7007 was discovered by astronomer John Herschel on July 8, 1834. In NGC 7007, there is counter-rotating disk of ionized gas that counter-rotates with respect to the stars; this indicates an external origin of the gas such as accretion. NGC 7079 Lenticular galaxy List of NGC objects NGC 7007 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images
NGC 7002 is a large elliptical galaxy around 320 million Light-years away from Earth in the constellation of Indus. The galaxy was discovered by English astronomer John Herschel on September 30, 1834. NGC 7002 is part of a group of galaxies that contains the nearby galaxy NGC 7004. IC 1101 Massive elliptical galaxy, one of the largest known galaxies M87 Famous large elliptical galaxy about 50 mly in the constellation Virgo. List of NGC objects Elliptical galaxy NGC 7002 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images
NGC 7006 is a globular cluster in the constellation Delphinus. NGC 7006 resides in the outskirts of the Milky Way, it is about 135,000 light-years away, five times the distance between the Sun and the centre of the galaxy, it is part of the galactic halo. This spherical region of the Milky Way is made up of dark matter and sparsely distributed stellar clusters. NGC 7006 appears in the science fiction novel Beyond the Farthest Star by Edgar Rice Burroughs, where it is used as a point of reference by the inhabitants of the planet Poloda to determine the approximate location of Earth. NGC 7006 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images
NGC 7013 is a nearby spiral or lenticular galaxy estimated to be around 37 to 41.4 million light-years away from Earth in the constellation of Cygnus. NGC 7013 was discovered by English astronomer William Herschel on July 17, 1784 and was observed by his son, astronomer John Herschel on September 15, 1828. NGC 7013 is tilted 90 ° to the Earth's line of sight. However, NGC 7013 is classified as either as a spiral galaxy with wound arms or as a lenticular galaxy. NGC 7013 is considered part of a class of galactic nuclei, defined by their spectral line emissions, called low-ionization nuclear emission-line region galaxies or LINERs; the galaxy appears to have two rings in its structure. The inner ring appears to disconnect from the central bulge while the stars in the outer ring appear to have little spiral pattern. Optical images of NGC 7013 show that it has a small bulge with a bright inner ring and a faint disk both crossed by dust lanes. A longer exposure of the galaxy made by the Palomar Observatory-National Geographic Sky Survey shows an extended disk around the bulge and the inner ring.
The disk shows little structure except for a faint, thin spiral-like feature running through the galaxy. The neutral atomic hydrogen distribution in NGC 7013 is located in the two rings. In between the two rings there is a low concentration of interstellar medium; the low level of neutral atomic hydrogen in the disk of NGC 7013 and the reddish color of the galaxy suggests that the gas content of the galactic disc has fallen below the threshold at which star formation is to take place. The small bulge-to-disk ratio and the slow rotation velocity show that NGC 7013 is a low-mass, low-density galaxy unlike the more luminous, typical lenticular galaxies; the galaxy may thus be a former late-type spiral galaxy which have exhausted most of its interstellar gas, either by star formation or by internal sweeping. Black Eye Galaxy NGC 4414 List of NGC objects NGC 7020 NGC 7013 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images
SIMBAD is an astronomical database of objects beyond the Solar System. It is maintained by the Centre de données astronomiques de France. SIMBAD was created by merging the Catalog of Stellar Identifications and the Bibliographic Star Index as they existed at the Meudon Computer Centre until 1979, expanded by additional source data from other catalogues and the academic literature; the first on-line interactive version, known as Version 2, was made available in 1981. Version 3, developed in the C language and running on UNIX stations at the Strasbourg Observatory, was released in 1990. Fall of 2006 saw the release of Version 4 of the database, now stored in PostgreSQL, the supporting software, now written in Java; as of 10 February 2017, SIMBAD contains information for 9,099,070 objects under 24,529,080 different names, with 327,634 bibliographical references and 15,511,733 bibliographic citations. The minor planet 4692 SIMBAD was named in its honour. Planetary Data System – NASA's database of information on SSSB, maintained by JPL and Caltech.
NASA/IPAC Extragalactic Database – a database of information on objects outside the Milky Way maintained by JPL. NASA Exoplanet Archive – an online astronomical exoplanet catalog and data service Bibcode SIMBAD, Strasbourg SIMBAD, Harvard
Type II supernova
A Type II supernova results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 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 observed in the spiral arms of galaxies and in H II regions, but not in elliptical galaxies. 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 higher temperatures and pressures, causing shorter stellar life spans; the degeneracy pressure of electrons and the energy generated by these fusion reactions are sufficient to counter the force of gravity and prevent the star from collapsing, maintaining stellar equilibrium. The star fuses higher mass elements, starting with hydrogen and helium, progressing up through the periodic table until a core of iron and nickel is produced.
Fusion of iron or nickel produces no net energy output, so no further fusion can take place, leaving the nickel–iron core inert. Due to the lack of energy output creating outward thermal pressure, the core contracts due to gravity until the overlying weight of the star can be supported by electron degeneracy pressure; when the compacted mass of the inert core exceeds the Chandrasekhar limit of about 1.4 M☉, electron degeneracy is no longer sufficient to counter the gravitational compression. A cataclysmic implosion of the core takes place within seconds. Without the support of the now-imploded inner core, the outer core collapses inwards under gravity and reaches a velocity of up to 23% of the speed of light and the sudden compression increases the temperature of the inner core to up to 100 billion kelvins. Neutrons and neutrinos are formed via reversed beta-decay, releasing about 1046 joules in a ten-second burst; the collapse of the inner core is halted by neutron degeneracy, causing the implosion to rebound and bounce outward.
The energy of this expanding shock wave is sufficient to disrupt the overlying stellar material and accelerate it to escape velocity, forming a supernova explosion. The shock wave and high temperature and pressure dissipate but are present for long enough to allow for a brief period during which the production of elements heavier than iron occurs. Depending on initial size of the star, the remnants of the core form a black hole; because of the underlying mechanism, the resulting supernova is described as a core-collapse supernova. There exist several categories of Type II supernova explosions, which are categorized based on the resulting light curve—a graph of luminosity versus time—following the explosion. Type II-L supernovae show a steady decline of the light curve following the explosion, whereas Type II-P display a period of slower decline in their light curve followed by a normal decay. Type Ib and Ic supernovae are a type of core-collapse supernova for a massive star that has shed its outer envelope of hydrogen and helium.
As a result, they appear to be lacking in these elements. Stars far more massive than the sun evolve in more complex ways. In the core of the star, hydrogen is fused into helium, releasing thermal energy that heats the sun's core and provides outward pressure that supports the sun's layers against collapse in a process known as stellar or hydrostatic equilibrium; the helium produced in the core accumulates there since temperatures in the core are not yet high enough to cause it to fuse. As the hydrogen at the core is exhausted, fusion starts to slow down, gravity causes the core to contract; this contraction raises the temperature high enough to initiate a shorter phase of helium fusion, which accounts for less than 10% of the star's total lifetime. In stars with fewer than eight solar masses, the carbon produced by helium fusion does not fuse, the star cools to become a white dwarf. White dwarf stars, if they have a near companion, may become Type Ia supernovae. A much larger star, however, is massive enough to create temperatures and pressures needed to cause the carbon in the core to begin to fuse when the star contracts at the end of the helium-burning stage.
The cores of these massive stars become layered like onions as progressively heavier atomic nuclei build up at the center, with an outermost layer of hydrogen gas, surrounding a layer of hydrogen fusing into helium, surrounding a layer of helium fusing into carbon via the triple-alpha process, surrounding layers that fuse to progressively heavier elements. As a star this massive evolves, it undergoes repeated stages where fusion in the core stops, the core collapses until the pressure and temperature are sufficient to begin the next stage of fusion, reigniting to halt collapse; the factor limiting this process is the amount of energy, released through fusion, dependent on the binding energy that holds together these atomic nuclei. Each additional step produces progressively heavier nuclei, which release progressively less energy when fusing. In addition, from carbon-burning onwards, energy loss via neutrino production becomes significant, leading to a higher rate of reaction than would otherwise take place.
This continues until nickel-56 is produced, which decays radioactively into cobalt-56 and iron-56 over the course of a few months. As iron and nickel have the highest binding energy per nucleon of all the elements, energy cannot be produced at the core by fusion, a nickel-iron core grows; this core is under huge gravitational pressure. As there is no fusion to further raise the s
The Iris Nebula known as NGC 7023 and Caldwell 4, is a bright reflection nebula and Caldwell object in the constellation Cepheus. NGC 7023 is the cluster within the nebula, LBN 487, the nebula is lit by a magnitude +7 star, SAO 19158, it shines at magnitude +6.8. It is located near the Mira-type variable star T Cephei, near the bright magnitude +3.23 variable star Beta Cephei. It is six light-years across. Pasachoff, Jay M.. "Atlas of the Sky". Stars and Planets. New York, New York: Peterson Field Guides. Pp. 578 pg. ISBN 978-0-395-93432-6. Caldwell-Moore, Sir Patrick. Firefly Atlas of the Universe. Firefly Books Limited. ISBN 978-1-55297-819-1. "NGC 7023". SIMBAD. Centre de données astronomiques de Strasbourg. SEDS – NGC 7023 VizieR – NGC 7023 NED – NGC 7023 Dark Atmospheres Photography – Iris Nebula NGC 7023 See NGC 7023 in WorldWide Telescope Iris Nebula on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images