A supernova (plural: supernovae or supernovas) is a stellar explosion. The Chandra X-ray Observatory is a Satellite launched on STS-93 by NASA on July 23, 1999. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study An explosion is a sudden increase in Volume and release of Energy in an extreme manner usually with the generation of high Temperatures and the release They are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy before fading from view over several weeks or months. A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter During this short interval, a supernova can radiate as much energy as the Sun could emit over its life span. Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός The Sun (Sol is the Star at the center of the Solar System.  The explosion expels much or all of a star's material at a velocity of up to a tenth the speed of light, driving a shock wave into the surrounding interstellar medium. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant. A supernova remnant ( SNR) is the structure resulting from the gigantic explosion of a Star in a Supernova.
Several types of supernovae exist that may be triggered in one of two ways, involving either turning off or suddenly turning on the production of energy through nuclear fusion. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus After the core of an aging massive star ceases to generate energy from nuclear fusion, it may undergo sudden gravitational collapse into a neutron star or black hole, releasing gravitational potential energy that heats and expels the star's outer layers. Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth Gravitational collapse in Astronomy is the inward fall of a massive body under the influence of the force of Gravity. A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e Potential energy can be thought of as Energy stored within a physical system Alternatively, a white dwarf star may accumulate sufficient material from a stellar companion (usually through accretion, rarely via a merger) to raise its core temperature enough to ignite carbon fusion, at which point it undergoes runaway nuclear fusion, completely disrupting it. A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. A binary star is a Star system consisting of two Stars orbiting around their Center of mass. In Astrophysics, the term accretion is used for at least two distinct processes Carbon detonation is a violent re-ignition of thermonuclear fusion in a dead star, which produces a Type Ia supernovae. The carbon burning process is a set of Nuclear fusion reactions that take place in massive Stars (at least 4 MSun at birth that have used up Thermal runaway refers to a situation where an increase in temperature changes the conditions in a way that causes a further increase in temperature leading to a destructive result Stellar cores whose furnaces have permanently gone out collapse when their masses exceed the Chandrasekhar limit, while accreting white dwarfs ignite as they approach this limit (roughly 1. The Chandrasekhar limit limits the mass of bodies made from Electron-degenerate matter, a dense form of matter which consists of nuclei immersed in a gas of Electrons 38 times the mass of the Sun). The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. White dwarfs are also subject to a different, much smaller type of thermonuclear explosion fueled by hydrogen on their surfaces called a nova. The CNO cycle (for Carbon - Nitrogen - Oxygen) or sometimes Bethe-Weizsäcker-cycle, is one of two sets of fusion reactions A nova (pl novae or novas) is a Cataclysmic nuclear explosion caused by the accretion of hydrogen onto the surface of a White Solitary stars with a mass below approximately nine solar masses, such as the Sun itself, evolve into white dwarfs without ever becoming supernovae. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies.
On average, supernovae occur about once every 50 years in a galaxy the size of the Milky Way and play a significant role in enriching the interstellar medium with heavy elements. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. Furthermore, the expanding shock waves from supernova explosions can trigger the formation of new stars. 
Nova (plural novae) means "new" in Latin, referring to what appears to be a very bright new star shining in the celestial sphere; the prefix "super-" distinguishes supernovae from ordinary novae, which also involve a star increasing in brightness, though to a lesser extent and through a different mechanism. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. In Astronomy and Navigation, the celestial sphere is an imaginary rotating Sphere of "gigantic Radius " An affix is a Morpheme that is attached to a stem to form a word A nova (pl novae or novas) is a Cataclysmic nuclear explosion caused by the accretion of hydrogen onto the surface of a White According to Merriam-Webster's Collegiate Dictionary, the word supernova was first used in print in 1926. Webster's Dictionary is the name given to a common type of English language dictionary in the United States.
The earliest recorded supernova, SN 185, was viewed by Chinese astronomers in 185 CE. SN 185 was a Supernova which appeared in the year 185 near the direction of Alpha Centauri, between the constellations Circinus and Centaurus Astronomy in China has a very long history Oracle bones from the Shang Dynasty ( 2nd millennium BC) record eclipses and novae Events By place Roman Empire Pertinax quells the mutiny of the British Roman legions Perennis his family The brightest recorded supernova was the SN 1006, which was described in detail by Chinese and Arab astronomers. SN 1006 was a Supernova, widely seen on Earth beginning in the year 1006 CE Earth was about 7200 light-years away from the supernova China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National The widely observed supernova SN 1054 produced the Crab Nebula. SN 1054 (Crab Supernova was a Supernova that was widely seen on Earth in the year 1054 The Crab Nebula  (catalogue designations M 1 NGC 1952 Taurus A is a Supernova remnant and Pulsar wind nebula in the Constellation Supernovae SN 1572 and SN 1604, the last to be observed with the naked eye in the Milky Way galaxy, had notable effects on the development of astronomy in Europe because they were used to argue against the Aristotelian idea that the world beyond the Moon and planets was immutable. SN 1572 ( Tycho's Supernova, Tycho's Nova) "B Cassiopeiae" (B Cas or 3C 10 was a Supernova of Type Ia in the Supernova 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a Supernova which occurred in the Milky Way, The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. 
Since the development of the telescope, the field of supernova discovery has enlarged to other galaxies, starting with the 1885 observation of supernova S Andromedae in the Andromeda galaxy. A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation. |- style="background-color #A0B0FF" colspan="3"| Database References |- bgcolor="#FFFAFA" | Simbad || Data|- bgcolor="#FFFAFA" The Andromeda Galaxy (ænˈdrɒmədə also known as Messier 31, M31, or NGC 224; often referred to as the Great Andromeda Supernovae provide important information on cosmological distances.  During the twentieth century, successful models for each type of supernova were developed, and scientists' comprehension of the role of supernovae in the star formation process is growing.
Some of the most distant supernovae recently observed appeared dimmer than expected. This has provided evidence that the expansion of the universe may be accelerating. The accelerating universe is the observation that the universe appears to be expanding at an accelerated rate 
Because supernovae are relatively rare events, occurring about once every 50 years in a galaxy like the Milky Way, many galaxies must be monitored regularly in order to obtain a good sample of supernovae to study.
Supernovae in other galaxies cannot be predicted with any meaningful accuracy. Normally, when they are discovered, they are already in progress.  Most scientific interest in supernovae—as standard candles for measuring distance, for example—require an observation of their peak luminosity. A standard candle is an astronomical object that has a known Luminosity. It is therefore important to discover them well before they reach their maximum. Amateur astronomers, who greatly outnumber professional astronomers, have played an important role in finding supernovae, typically by looking at some of the closer galaxies through an optical telescope and comparing them to earlier photographs. Amateur astronomy, a subset of Astronomy, is a Hobby whose participants enjoy studying and observing celestial objects An optical telescope is a Telescope which is used to gather and focus light mainly from the visible part of the Electromagnetic spectrum
Towards the end of the 20th century, astronomers increasingly turned to computer-controlled telescopes and CCDs for hunting supernovae. A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors While such systems are popular with amateurs, there are also larger installations like the Katzman Automatic Imaging Telescope. The Katzman Automatic Imaging Telescope (KAIT is an automated telescope used in the search for Supernovae The KAIT is a computer-controlled Reflecting telescope  Recently, the Supernova Early Warning System (SNEWS) project has also begun using a network of neutrino detectors to give early warning of a supernova in the Milky Way galaxy. The SuperNova Early Warning System (SNEWS is a network of Neutrino detectors designed to give early warning to Astronomers in the event of a supernova Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost  A neutrino is a particle that is produced in great quantities by a supernova explosion, and it is not absorbed by the interstellar gas and dust of the galactic disk. A subatomic particle is an elementary or composite Particle smaller than an Atom.
Supernova searches fall into two classes: those focused on relatively nearby events and those looking for explosions farther away. Because of the expansion of the universe, the distance to a remote object with a known emission spectrum can be estimated by measuring its Doppler shift (or redshift); on average, more distant objects recede with greater velocity than those nearby, and so have a higher redshift. The metric expansion of space is the averaged increase of metric (i The Doppler effect (or Doppler shift) named after Christian Doppler, is the change in Frequency and Wavelength of a Wave for In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by Thus the search is split between high redshift and low redshift, with the boundary falling around a redshift range of z = 0. 1–0. 3—where z is a dimensionless measure of the spectrum's frequency shift.
High redshift searches for supernovae usually involve the observation of supernova light curves. These are useful for standard or calibrated candles to generate Hubble diagrams and make cosmological predictions. At low redshift, supernova spectroscopy is more practical than at high redshift, and this is used to study the physics and environments of supernovae.  Low redshift observations also anchor the low distance end of the Hubble curve, which is a plot of distance versus redshift for visible galaxies. 
Supernova discoveries are reported to the International Astronomical Union's Central Bureau for Astronomical Telegrams, which sends out a circular with the name it assigns to it. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member The Central Bureau for Astronomical Telegrams ( CBAT) is the official international Clearing house for information relating to transient astronomical events The name is formed by the year of discovery, immediately followed by a one or two-letter designation. The first 26 supernovae of the year get designated with an upper case letter from A to Z. Afterward, pairs of lower-case letters are used, starting with aa, ab, and so on.  Professional and amateur astronomers find several hundred supernovae each year (367 in 2005, 551 in 2006 and 572 in 2007). For example, the last supernova of 2005 was SN 2005nc, indicating that it was the 367th supernova found in 2005. 
Historical supernovae are known simply by the year they occurred: SN 185, SN 1006, SN 1054, SN 1572 (Tycho's Nova) and SN 1604 (Kepler's Star). SN 185 was a Supernova which appeared in the year 185 near the direction of Alpha Centauri, between the constellations Circinus and Centaurus SN 1006 was a Supernova, widely seen on Earth beginning in the year 1006 CE Earth was about 7200 light-years away from the supernova SN 1054 (Crab Supernova was a Supernova that was widely seen on Earth in the year 1054 SN 1572 ( Tycho's Supernova, Tycho's Nova) "B Cassiopeiae" (B Cas or 3C 10 was a Supernova of Type Ia in the Supernova 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a Supernova which occurred in the Milky Way, Since 1885, the letter notation was used, even if there was only one supernova discovered that year (e. g. SN 1885A, 1907A, etc. )—this last happened with SN 1947A. The standard abbreviation "SN" is an optional prefix.
As part of the attempt to understand supernovae, astronomers have classified them according to the absorption lines of different chemical elements that appear in their spectra. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared Astronomical spectroscopy is the technique of Spectroscopy used in Astronomy. The first element for a division is the presence or absence of a line caused by hydrogen. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 If a supernova's spectrum contains a line of hydrogen (known as the Balmer series in the visual portion of the spectrum) it is classified Type II; otherwise it is Type I. The Balmer series or Balmer lines in Atomic physics, is the designation of one of a set of six different named series describing the Spectral line emissions Among those types, there are subdivisions according to the presence of lines from other elements and the shape of the light curve (a graph of the supernova's apparent magnitude versus time). In Astronomy, a light curve is a graph of light intensity of a Celestial object or region as a function of time The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 
|Type Ia||Lacks hydrogen and presents a singly-ionized silicon (Si II) line at 615. A Type Ia supernova is a sub-category of cataclysmic Variable Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 0 nm (nanometers), near peak light. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a|
|Type Ib||Non-ionized helium (He I) line at 587. Types Ib and Ic supernovae are categories of stellar explosions Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical 6 nm and no strong silicon absorption feature near 615 nm.|
|Type Ic||Weak or no helium lines and no strong silicon absorption feature near 615 nm. Types Ib and Ic supernovae are categories of stellar explosions|
|Type IIP||Reaches a "plateau" in its light curve|
|Type IIL||Displays a "linear" decrease in its light curve (linear in magnitude versus time). Type II Supernova, or core-collapse supernova, is a sub-category of cataclysmic Variable stars that results from the internal collapse and violent explosion Type II Supernova, or core-collapse supernova, is a sub-category of cataclysmic Variable stars that results from the internal collapse and violent explosion |
The supernovae of Type II can also be sub-divided based on their spectra. While most Type II supernova show very broad emission lines which indicate expansion velocities of many thousands of kilometres per second, some have relatively narrow features. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared These are called Type IIn, where the "n" stands for "narrow". 
A few supernovae, such as SN 1987K and SN 1993J, appear to change types: they show lines of hydrogen at early times, but, over a period of weeks to months, become dominated by lines of helium. The term "Type IIb" is used to describe the combination of features normally associated with Types II and Ib. 
There are several means by which a supernova of this type can form, but they share a common underlying mechanism. A Type Ia supernova is a sub-category of cataclysmic Variable If a carbon-oxygen[a] white dwarf accreted enough matter to reach the Chandrasekhar limit of about 1. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. The Chandrasekhar limit limits the mass of bodies made from Electron-degenerate matter, a dense form of matter which consists of nuclei immersed in a gas of Electrons 38 solar masses (for a non-rotating star), it would no longer be able to support the bulk of its plasma through electron degeneracy pressure and would begin to collapse. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. Electron degeneracy pressure is a consequence of the Pauli exclusion principle, which states that two Fermions cannot occupy the same Quantum state at the However, the current view is that this limit is not normally attained; increasing temperature and density inside the core ignite carbon fusion as the star approaches the limit (to within about 1%), before collapse is initiated. Carbon detonation is a violent re-ignition of thermonuclear fusion in a dead star, which produces a Type Ia supernovae. The carbon burning process is a set of Nuclear fusion reactions that take place in massive Stars (at least 4 MSun at birth that have used up  Within a few seconds, a substantial fraction of the matter in the white dwarf undergoes nuclear fusion, releasing enough energy (1–2 × 1044 joules) to unbind the star in a supernova explosion. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity  An outwardly expanding shock wave is generated, with matter reaching velocities on the order of 5,000–20,000 km/s, or roughly 3% of the speed of light. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called There is also a significant increase in luminosity, reaching an absolute magnitude of -19. In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard 3 (or 5 billion times brighter than the Sun), with little variation. 
One model for the formation of this category of supernova is a close binary star system. A binary star is a Star system consisting of two Stars orbiting around their Center of mass. The larger of the two stars is the first to evolve off the main sequence, and it expands to form a red giant. The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness A red giant is a luminous Giant star of low or intermediate mass (roughly 0  The two stars now share a common envelope, causing their mutual orbit to shrink. The giant star then sheds most of its envelope, losing mass until it can no longer continue nuclear fusion. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus At this point it becomes a white dwarf star, composed primarily of carbon and oxygen.  Eventually the secondary star also evolves off the main sequence to form a red giant. Matter from the giant is accreted by the white dwarf, causing the latter to increase in mass.
Another model for the formation of a Type Ia explosion involves the merger of two white dwarf stars, with the combined mass momentarily exceeding the Chandrasekhar limit.  A white dwarf could also accrete matter from other types of companions, including a main sequence star (if the orbit is sufficiently close).
Type Ia supernovae follow a characteristic light curve—the graph of luminosity as a function of time—after the explosion. In Astronomy, a light curve is a graph of light intensity of a Celestial object or region as a function of time This luminosity is generated by the radioactive decay of nickel-56 through cobalt-56 to iron-56. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Cobalt (ˈkoʊbɒlt is a hard lustrous silver-grey Metal, a Chemical element with symbol Co. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26  The peak luminosity of the light curve was believed to be consistent across Type Ia supernovae (the vast majority of which are initiated with a uniform mass via the accretion mechanism), allowing them to be used as a secondary standard candle to measure the distance to their host galaxies. A standard candle is an astronomical object that has a known Luminosity. A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter  However, recent discoveries reveal that there is some evolution in the average lightcurve width, and thus in the intrinsic luminosity of Supernovae, although significant evolution is found only over a large redshift baseline. 
These events, like supernovae of Type II, are probably massive stars running out of fuel at their centers; however, the progenitors of Types Ib and Ic have lost most of their outer (hydrogen) envelopes due to strong stellar winds or else from interaction with a companion. A stellar wind is a flow of neutral or charged gas ejected from the upper atmosphere of a Star.  Type Ib supernovae are thought to be the result of the collapse of a massive Wolf-Rayet star. There is some evidence that a few percent of the Type Ic supernovae may be the progenitors of gamma ray bursts (GRB), though it is also believed that any hydrogen-stripped, Type Ib or Ic supernova could be a GRB, dependent upon the geometry of the explosion. Gamma-ray bursts ( GRB s are the most luminous electromagnetic events occurring in the Universe since the Big Bang. 
Stars with at least nine solar masses of material evolve in a complex fashion. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies.  In the core of the star, hydrogen is fused into helium and the thermal energy released creates an outward pressure, which maintains the core in hydrostatic equilibrium and prevents collapse. Thermal energy is the sum of the sensible energy and latent energy. Hydrostatic equilibrium occurs when compression due to Gravity is balanced by a Pressure gradient which creates a Pressure gradient force in the opposite
When the core's supply of hydrogen is exhausted, this outward pressure is no longer created. The core begins to collapse, causing a rise in temperature and pressure which becomes great enough to ignite the helium and start a helium-to-carbon fusion cycle, creating sufficient outward pressure to halt the collapse. Gravitational collapse in Astronomy is the inward fall of a massive body under the influence of the force of Gravity. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 The core expands and cools slightly, with a hydrogen-fusion outer layer, and a hotter, higher pressure, helium-fusion center. (Other elements such as magnesium, sulfur and calcium are also created and in some cases burned in these further reactions. Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 )
This process repeats several times, and each time the core collapses and the collapse is halted by the ignition of a further process involving more massive nuclei and higher temperatures and pressures. Each layer is prevented from collapse by the heat and outward pressure of the fusion process in the next layer inward; each layer also burns hotter and quicker than the previous one – the final burn of silicon to nickel consumes its fuel in around one day, or a few days.  The star becomes layered like an onion, with the burning of more easily fused elements occurring in larger shells. 
In the later stages, increasingly heavier elements undergo nuclear fusion, and the binding energy of the relevant nuclei increases. Binding energy is the Mechanical energy required to disassemble a whole into separate parts Fusion produces progressively lower levels of energy, and also at higher core energies photodisintegration and electron capture occur which cause energy loss in the core and a general acceleration of the fusion processes to maintain equilibrium. Photodisintegration is a physical process in which extremely high energy Gamma rays interact with an Atomic nucleus and cause it to enter an excited state which immediately Electron capture (sometimes called inverse beta decay) is a Decay mode for Isotopes that will occur when there are too many Protons in the  This escalation culminates with the production of nickel-56, which is unable to produce energy through fusion (but does produce iron-56 through radioactive decay). In Astrophysics, Silicon burning is a two week sequence of Nuclear fusion reactions that occur in massive Stars with a minimum of about 8–11  As a result, a nickel-iron core builds up that cannot produce any further outward pressure on a scale needed to support the rest of the structure. It can only support the overlaying mass of the star through the degeneracy pressure of electrons in the core. Degenerate matter is matter which has sufficiently high Density that the dominant contribution to its Pressure rises from the Pauli Exclusion The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J If the star is sufficiently large, then the iron-nickel core will eventually exceed the Chandrasekhar limit (1. The Chandrasekhar limit limits the mass of bodies made from Electron-degenerate matter, a dense form of matter which consists of nuclei immersed in a gas of Electrons 38 solar masses), at which point this mechanism catastrophically fails. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. The forces holding atomic nuclei apart in the innermost layer of the core suddenly give way, the core implodes due to its own mass, and no further fusion process can ignite or prevent collapse this time. Implosion is a process in which objects are destroyed by collapsing in on themselves 
The core collapses in on itself with velocities reaching 70,000 km/s (0. Gravitational collapse in Astronomy is the inward fall of a massive body under the influence of the force of Gravity. 23c), resulting in a rapid increase in temperature and density. The energy loss processes operating in the core cease to be in equilibrium. Through photodisintegration, gamma rays decompose iron into helium nuclei and free neutrons, absorbing energy, whilst electrons and protons merge via electron capture, producing neutrons and electron neutrinos which escape. Photodisintegration is a physical process in which extremely high energy Gamma rays interact with an Atomic nucleus and cause it to enter an excited state which immediately Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive Electron capture (sometimes called inverse beta decay) is a Decay mode for Isotopes that will occur when there are too many Protons in the Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost
In a typical Type II supernova, the newly formed neutron core has an initial temperature of about 100 billion kelvin (100 GK); 6000 times the temperature of the sun's core. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic Much of this thermal energy must be shed for a stable neutron star to form (otherwise the neutrons would "boil away"), and this is accomplished by a further release of neutrinos.  These 'thermal' neutrinos form as neutrino-antineutrino pairs of all flavors, and total several times the number of electron-capture neutrinos. Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a Neutrino created with a specific Lepton  About 1046 joules of gravitational energy—about 10% of the star's rest mass—is converted into a ten-second burst of neutrinos; the main output of the event.  These carry away energy from the core and accelerate the collapse, while some neutrinos may be later absorbed by the star's outer layers to provide energy to the supernova explosion. 
The inner core eventually reaches typically 30 km diameter, and a density comparable to that of an atomic nucleus, and further collapse is abruptly stopped by strong force interactions and by degeneracy pressure of neutrons. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and Degenerate matter is matter which has sufficiently high Density that the dominant contribution to its Pressure rises from the Pauli Exclusion The infalling matter, suddenly halted, rebounds, producing a shock wave that propagates outward. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called Computer simulations indicate that this expanding shock does not directly cause the supernova explosion; rather, it stalls within milliseconds in the outer core as energy is lost through the dissociation of heavy elements, and a process that is not clearly understood is necessary to allow the outer layers of the core to reabsorb around 1044 joules[b] (1 foe) of energy, producing the visible explosion. A millisecond (from Milli- and Second; abbreviation ms is one thousandth of a Second. A foe is a unit of Energy equal to 1044 Joules or 1051 Ergs used to measure the large amount of energy produced by a Supernova  Current research focuses upon a combination of neutrino reheating, rotational and magnetic effects as the basis for this process. A rotation is a movement of an object in a circular motion A two- Dimensional object rotates around a center (or point) of rotation In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges 
When the progenitor star is below about 20 solar masses (depending on the strength of the explosion and the amount of material that falls back), the degenerate remnant of a core collapse is a neutron star. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type  Above this mass the remnant collapses to form a black hole. A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e  (This type of collapse is one of many candidate explanations for gamma ray bursts—producing a large burst of gamma rays through a still theoretical hypernova explosion. Gamma-ray bursts ( GRB s are the most luminous electromagnetic events occurring in the Universe since the Big Bang. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions Hypernova (pl hypernovae) refers to an exceptionally large Star that collapses at the end of its lifespan—for example a collapsar, or a large ) The theoretical limiting mass for this type of core collapse scenario was estimated around 40–50 solar masses.
Above 50 solar masses, stars were believed to collapse directly into a black hole without forming a supernova explosion, although uncertainties in models of supernova collapse make accurate calculation of these limits difficult. In fact recent evidence has shown stars in the range of about 140–250 solar masses, with a relatively low proportion of elements more massive than helium, may be capable of forming pair-instability supernovae without leaving behind a black hole remnant. A pair instability Supernova occurs when Pair production, the production of free Electrons and Positrons in the collision between Atomic This rare type of supernova is formed by an alternate mechanism (partially analogous to that of Type Ia explosions) that does not require an iron core. An example is the Type II supernova SN 2006gy, with an estimated 150 solar masses, that demonstrated the explosion of such a massive star differed fundamentally from previous theoretical predictions. SN 2006gy was an extremely energetic Supernova, sometimes referred to as a Hypernova or Quark-nova, that was discovered on September 18, 
The light curves for Type II supernovae are distinguished by the presence of hydrogen Balmer absorption lines in the spectra. The Balmer series or Balmer lines in Atomic physics, is the designation of one of a set of six different named series describing the Spectral line emissions These light curves have an average decay rate of 0. 008 magnitudes per day; much lower than the decay rate for Type I supernovae. In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard Type II are sub-divided into two classes, depending on whether there is a plateau in their light curve (Type II-P) or a linear decay rate (Type II-L). The net decay rate is higher at 0. 012 magnitudes per day for Type II-L compared to 0. 0075 magnitudes per day for Type II-P. The difference in the shape of the light curves is believed to be caused, in the case of Type II-L supernovae, by the expulsion of most of the hydrogen envelope of the progenitor star. 
The plateau phase in Type II-P supernovae is due to a change in the opacity of the exterior layer. Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation especially visible Light. The shock wave ionizes the hydrogen in the outer envelope, which greatly increases the opacity. Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons This prevents photons from the inner parts of the explosion from escaping. Once the hydrogen cools sufficiently to recombine, the outer layer becomes transparent. 
Of the Type II supernovae with unusual features in their spectra, Type IIn supernovae may be produced by the interaction of the ejecta with circumstellar material.  Type IIb supernovae are likely massive stars which have lost most, but not all, of their hydrogen envelopes through tidal stripping by a companion star. The tidal force is a secondary effect of the Force of Gravity and is responsible for the Tides It arises because the gravitational acceleration experienced As the ejecta of a Type IIb expands, the hydrogen layer quickly becomes optically thin and reveals the deeper layers. 
A long-standing puzzle surrounding supernovae has been a need to explain why the compact object remaining after the explosion is given a large velocity away from the core.  (Neutron stars are observed, as pulsars, to have high velocities; black holes presumably do as well, but are far harder to observe in isolation. A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type Pulsars are highly magnetized rotating Neutron stars that emit a beam of Electromagnetic radiation in the form of radio waves A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e ) This kick can be substantial, propelling an object of more than a solar mass at a velocity of 500 km/s or greater. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. This displacement is believed to be caused by an asymmetry in the explosion, but the mechanism by which this momentum is transferred to the compact object has remained a puzzle. Some explanations for this kick include convection in the collapsing star and jet production during neutron star formation.
One explanation for the asymmetry in the explosion is large-scale convection above the core. The convection can create variations in the local abundances of elements, resulting in uneven nuclear burning during the collapse, bounce and resulting explosion. 
Another explanation is that accretion of gas onto the central neutron star can create a disk that drives highly directional jets, propelling matter at a high velocity out of the star, and driving transverse shocks that completely disrupt the star. An accretion disc (or accretion disk) is a structure (often a Circumstellar disk) formed by diffuse material in orbital motion around a central body These jets might play a crucial role in the resulting supernova explosion.  (A similar model is now favored for explaining long gamma ray bursts. Gamma-ray bursts ( GRB s are the most luminous electromagnetic events occurring in the Universe since the Big Bang. )
Initial asymmetries have also been confirmed in Type Ia supernova explosions through observation. This result may mean that the initial luminosity of this type of supernova may depend on the viewing angle. However, the explosion becomes more symmetrical with the passage of time. Early asymmetries are detectable by measuring the polarization of the emitted light. 
Because they have a similar functional model, Types Ib, Ic and various Types II supernovae are collectively called Core Collapse supernovae. A fundamental difference between Type Ia and Core Collapse supernovae is the source of energy for the radiation emitted near the peak of the light curve. The progenitors of Core Collapse supernovae are stars with extended envelopes that can attain a degree of transparency with a relatively small amount of expansion. Most of the energy powering the emission at peak light is derived from the shock wave that heats and ejects the envelope. 
The progenitors of Type Ia supernovae, on the other hand, are compact objects, much smaller (but more massive) than the Sun, that must expand (and therefore cool) enormously before becoming transparent. Heat from the explosion is dissipated in the expansion and is not available for light production. The radiation emitted by Type Ia supernovae is thus entirely attributable to the decay of radionuclides produced in the explosion; principally nickel-56 (with a half-life of 6. A radionuclide is an Atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 1 days) and its daughter cobalt-56 (with a half-life of 77 days). Cobalt (ˈkoʊbɒlt is a hard lustrous silver-grey Metal, a Chemical element with symbol Co. Gamma rays emitted during this nuclear decay are absorbed by the ejected material, heating it to incandescence. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Incandescence is the emission of Light (visible Electromagnetic radiation) from a hot body due to its temperature
As the material ejected by a Core Collapse supernova expands and cools, radioactive decay eventually takes over as the main energy source for light emission in this case also. A bright Type Ia supernova may expel 0. 5–1. 0 solar masses of nickel-56, while a Core Collapse supernova probably ejects closer to 0. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. 1 solar mass of nickel-56. 
Supernovae are a key source of elements heavier than oxygen. Supernova nucleosynthesis is the production of new Chemical elements inside Supernovae It occurs primarily due to explosive Nucleosynthesis during explosive A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the These elements are produced by nuclear fusion (for iron-56 and lighter elements), and by nucleosynthesis during the supernova explosion for elements heavier than iron. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons Supernova are the most likely, although not undisputed, candidate sites for the r-process, which is a rapid form of nucleosynthesis that occurs under conditions of high temperature and high density of neutrons. The r-process is a Nucleosynthesis process occurring in core-collapse Supernovae (see also Supernova nucleosynthesis) responsible for the creation of approximately The reactions produce highly unstable nuclei that are rich in neutrons. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. These forms are unstable and rapidly beta decay into more stable forms. In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted
The r-process reaction, which is likely to occur in type II supernovae, produces about half of all the element abundance beyond iron, including plutonium, uranium and californium. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Californium (ˌkælɪˈforniəm is a Metallic Chemical element with the symbol Cf and Atomic number 98  The only other major competing process for producing elements heavier than iron is the s-process in large, old red giant stars, which produces these elements much more slowly, and which cannot produce elements heavier than lead. The S-process or slow-neutron -capture-process is a Nucleosynthesis process that occurs at relatively low neutron density and intermediate temperature conditions in Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly 
The remnant of a supernova explosion consists of a compact object and a rapidly expanding shock wave of material. A supernova remnant ( SNR) is the structure resulting from the gigantic explosion of a Star in a Supernova. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called This cloud of material sweeps up the surrounding interstellar medium during a free expansion phase, which can last for up to two centuries. The wave then gradually undergoes a period of adiabatic expansion, and will slowly cool and mix with the surrounding interstellar medium over a period of about 10,000 years. This article covers adiabatic processes in Thermodynamics. For adiabatic processes in Quantum mechanics, see Adiabatic process (quantum mechanics 
In standard astronomy, the Big Bang produced hydrogen, helium, and traces of lithium, while all heavier elements are synthesized in stars and supernovae. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Lithium (ˈlɪθiəm is a Chemical element with the symbol Li and Atomic number 3 Supernovae tend to enrich the surrounding interstellar medium with metals, which for astronomers means all of the elements other than hydrogen and helium and is a different definition than that used in chemistry.
These injected elements ultimately enrich the molecular clouds that are the sites of star formation. See also Solar nebula A molecular cloud, sometimes called a stellar nursery if Star formation is occurring within is a type of Interstellar  Thus, each stellar generation has a slightly different composition, going from an almost pure mixture of hydrogen and helium to a more metal-rich composition. Supernovae are the dominant mechanism for distributing these heavier elements, which are formed in a star during its period of nuclear fusion, throughout space. The different abundances of elements in the material that forms a star have important influences on the star's life, and may decisively influence the possibility of having planets orbiting it. A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is
The kinetic energy of an expanding supernova remnant can trigger star formation due to compression of nearby, dense molecular clouds in space. The kinetic energy of an object is the extra Energy which it possesses due to its motion The increase in turbulent pressure can also prevent star formation if the cloud is unable to lose the excess energy. 
Evidence from daughter products of short-lived radioactive isotopes shows that a nearby supernova helped determine the composition of the Solar System 4. A radionuclide is an Atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created The Solar System consists of the Sun and those celestial objects bound to it by Gravity. 5 billion years ago, and may even have triggered the formation of this system.  Supernova production of heavy elements over astronomic periods of time ultimately made the chemistry of life on Earth possible. Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as
A near-Earth supernova is an explosion resulting from the death of a star that occurs close enough to the Earth (roughly fewer than 100 light-years away) to have noticeable effects on its biosphere. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by The biosphere is the broadest level of ecological study the global sum of all Ecosystems. Gamma rays are responsible for most of the adverse effects a supernova can have on a living terrestrial planet. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions A terrestrial planet, telluric planet or rocky planet is a Planet that is primarily composed of Silicate rocks Within our In Earth's case, gamma rays induce a chemical reaction in the upper atmosphere, converting molecular nitrogen into nitrogen oxides, depleting the ozone layer enough to expose the surface to harmful solar and cosmic radiation. A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on The gamma ray burst from a nearby supernova explosion has been proposed as the cause of the end Ordovician extinction, which resulted in the death of nearly 60% of the oceanic life on Earth. Gamma-ray bursts ( GRB s are the most luminous electromagnetic events occurring in the Universe since the Big Bang. 
Speculation as to the effects of a nearby supernova on Earth often focuses on large stars as Type II supernova candidates. Several prominent stars within a few hundred light years from the Sun are candidates for becoming supernovae in as little as a millennium. One example is Betelgeuse, a red supergiant 427 light-years from Earth. Betelgeuse (ˈbiːtəldʒuːz or /ˈbɛtəldʒuːz/ ( α Ori α Orionis Alpha Orionis is a Semiregular variable star located 640 Light-years away from  Though spectacular, these "predictable" supernovae are thought to have little potential to affect Earth.
Recent estimates predict that a Type II supernova would have to be closer than eight parsecs (26 light-years) to destroy half of the Earth's ozone layer. History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838  Such estimates are mostly concerned with atmospheric modeling and considered only the known radiation flux from SN 1987A, a Type II supernova in the Large Magellanic Cloud. SN 1987A was a Supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby The Large Magellanic Cloud (LMC is a nearby Satellite galaxy of our own galaxy the Milky Way. Estimates of the rate of supernova occurrence within 10 parsecs of the Earth vary from once every 100 million years to once every one to ten billion years. 
Type Ia supernovae are thought to be potentially the most dangerous if they occur close enough to the Earth. Because Type Ia supernovae arise from dim, common white dwarf stars, it is likely that a supernova that could affect the Earth will occur unpredictably and take place in a star system that is not well studied. A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. One theory suggests that a Type Ia supernova would have to be closer than a thousand parsecs (3300 light-years) to affect the Earth.  The closest known candidate is IK Pegasi (see below). IK Pegasi (or HR 8210) is a Binary star system in the Constellation Pegasus. 
In 1996, astronomers at the University of Illinois at Urbana-Champaign theorized that traces of past supernovae might be detectable on Earth in the form of metal isotope signatures in rock strata. This article is about the flagship campus For other uses and locations of University of Illinois, see University of Illinois (disambiguation The University of In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes Subsequently, iron-60 enrichment has been reported in deep-sea rock of the Pacific Ocean by researchers from the Technical University of Munich. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 The Pacific Ocean is the largest of the Earth 's Oceanic divisions Technische Universität München ( TUM, technical university of Munich) is a research university with campuses in Munich, Garching, and 
Several large stars within the Milky Way have been suggested as possible supernovae within the next few thousand to hundred million years. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply These include Rho Cassiopeiae, Eta Carinae, RS Ophiuchi, the Kitt Peak Downes star KPD1930+2752, HD 179821, IRC+10420, VY Canis Majoris, Betelgeuse, Antares, and Spica. Rho Cassiopeiae (ρ Cas / ρ Cassiopeiae is a Yellow hypergiant in the constellation Cassiopeia. Eta Carinae (η Carinae or η Car is a Hypergiant Luminous blue variable Star in the Carina constellation. RS Ophiuchi ( RS Oph) is a Nova approximately 5000 Light-years away in the Constellation Ophiuchus. VY Canis Majoris ( VY CMa) is a red Hypergiant Star located in the constellation Canis Major. Betelgeuse (ˈbiːtəldʒuːz or /ˈbɛtəldʒuːz/ ( α Ori α Orionis Alpha Orionis is a Semiregular variable star located 640 Light-years away from Antares (α Scorpii / Alpha Scorpii is a Red supergiant Star in the Milky Way Galaxy and the sixteenth brightest star Spica (ˈspaɪkə (also known as α Vir / α Virginis / Alpha Virginis is the brightest star in the Constellation Virgo, and the 15th brightest star 
Many Wolf-Rayet stars, such as Gamma Velorum, WR 104, and those in the Quintuplet Cluster, are also considered possible precursor stars to a supernova explosion in the 'near' future. Gamma Velorum (γ Vel / γ Velorum is a Star system in the Constellation Vela. WR 104 is a Wolf-Rayet star located 8000 Light years from Earth at RA 18h02m04s
The nearest supernova candidate is IK Pegasi (HR 8210), located at a distance of only 150 light-years. IK Pegasi (or HR 8210) is a Binary star system in the Constellation Pegasus. This closely-orbiting binary star system consists of a main sequence star and a white dwarf, separated by only 31 million km. A binary star is a Star system consisting of two Stars orbiting around their Center of mass. A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand The dwarf has an estimated mass equal to 1. 15 times that of the Sun.  It is thought that several million years will pass before the white dwarf can accrete the critical mass required to become a Type Ia supernova.