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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] |
SN 1987A
SN 1987A was a Type II supernova in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It occurred approximately from Earth and was the closest observed supernova since Kepler's Supernova in 1604. Light and neutrinos from the explosion reached Earth on February 23, 1987, and it was designated "SN 1987A" as the first supernova discovered that year. Its brightness peaked in May of that year, with an apparent magnitude of about 3, brighter than the constellation's brightest star, Alpha Doradus. It was the first supernova that modern astronomers were able to study in great detail, and its observations have provided much insight into core-collapse supernovae. SN 1987A provided the first opportunity to confirm by direct observation the radioactive source of the energy for visible light emissions, by detecting predicted gamma-ray line radiation from two of its abundant radioactive nuclei. This proved the radioactive nature of the long-duration po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tycho's Supernova
SN 1572 ('' Tycho's Star'', ''Tycho's Nova'', ''Tycho's Supernova''), or B Cassiopeiae (B Cas), was a supernova of Type Ia in the constellation Cassiopeia, one of eight supernovae visible to the naked eye in historical records. It appeared in early November 1572 and was independently discovered by many individuals. Its supernova remnant has been observed optically but was first detected at radio wavelengths. It is often known as 3C 10, a radio-source designation, although increasingly as Tycho's supernova remnant. Historic description The appearance of the Milky Way supernova of 1572 belongs among the most important observation events in the history of astronomy. The appearance of the " new star" helped to revise ancient models of the heavens and to speed on a revolution in astronomy that began with the realisation of the need to produce better astrometric star catalogues, and thus the need for more precise astronomical observing instruments. It also challenged the Aristoteli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Dwarf
A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place in a white dwarf; what light it radiates is from its residual heat. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name ''white dwarf'' was coined by Willem Jacob Luyten in 1922. White dwarfs are thought to be the final stellar evolution, evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the stars in the Milky Way. After the hydrogen-stellar nucleosynthesis, fusing period of a main sequence, main-sequence star of Stellar mass, lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kepler's Supernova
SN 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a Type Ia supernova that occurred in the Milky Way, in the constellation Ophiuchus. Appearing in 1604, it is the most recent supernova in the Milky Way galaxy to have been unquestionably observed by the naked eye, occurring no farther than 6 kiloparsecs (20,000 light-years) from Earth. Before the adoption of the current naming system for supernovae, it was named for Johannes Kepler, the German astronomer who described it in '' De Stella Nova''. Observation Visible to the naked eye, Kepler's Star was brighter at its peak than any other star in the night sky, with an apparent magnitude of −2.5. It was visible during the day for over three weeks. Records of its sighting exist in European, Chinese, Korean, and Arabic sources. It was the second supernova to be observed in a generation (after SN 1572 seen by Tycho Brahe in Cassiopeia). No further supernovae have since been observed with certainty in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Evolution
Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the current age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from Gravitational collapse, collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main sequence star. Nuclear fusion powers a star for most of its existence. Initially the energy is generated by the fusion of hydrogen atoms at the stellar core, core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supernova Remnant
A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way. There are two common routes to a supernova: either a massive star may run out of fuel, ceasing to generate fusion energy in its core, and collapsing inward under the force of its own gravity to form a neutron star or a black hole; or a white dwarf star may accrete material from a companion star until it reaches a critical mass and undergoes a thermonuclear explosion. In either case, the resulting supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light (or approximately 30,000 km/s) and a strong shock wave forms ahead of the ejecta. That heats the upstream plasma up to temperatures well above millions of K. The shock continuou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sky, night; their immense distances from Earth make them appear as fixed stars, fixed points of light. The most prominent stars have been categorised into constellations and asterism (astronomy), asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated to stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy. A star's life star formation, begins with the gravitational collapse of a gaseous nebula of material largely comprising hydrogen, helium, and traces of heavier elements. Its stellar mass, total mass mainly determines it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Star
A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses the core past white dwarf star density to that of Atomic nucleus, atomic nuclei. Surpassed only by black holes, neutron stars are the second smallest and densest known class of stellar objects. Neutron stars have a radius on the order of and a mass of about . Stars that collapse into neutron stars have a total mass of between 10 and 25 solar masses (), or possibly more for those that are especially rich in Metallicity, elements heavier than hydrogen and helium. Once formed, neutron stars no longer actively generate heat and cool over time, but they may still evolve further through Stellar collision, collisions or Accretion (astrophysics), accretion. Most of the basic models for these objects imply that they are composed almost entirely o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Runaway
Thermal runaway describes a process that is accelerated by increased temperature, in turn releasing Thermal energy, energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the conditions in a way that causes a further increase in temperature, often leading to a destructive result. It is a kind of uncontrolled positive feedback. In chemistry (and chemical engineering), thermal runaway is associated with strongly exothermic reactions that are accelerated by temperature rise. In electrical engineering, thermal runaway is typically associated with increased Electric current, current flow and power dissipation. Thermal runaway can occur in civil engineering, notably when the heat released by large amounts of Concrete#Curing, curing concrete is not controlled. In astrophysics, runaway nuclear fusion reactions in stars can lead to nova and several types of supernova explosions, and also occur as a less dramatic event in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blue Supergiant Star
A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blue supergiants. Blue supergiants are found towards the top left of the Hertzsprung–Russell diagram, above and to the right of the main sequence. By analogy to the red giant branch for low-mass stars, this region is also called the blue giant branch. They are larger than the Sun but smaller than a red supergiant, with surface temperatures of 10,000–50,000 K and luminosities from about 10,000 to a million times that of the Sun. They are most often an evolutionary phase between high-mass, hydrogen-fusing main-sequence stars and helium-fusing red supergiants, although new research suggests they could be the result of stellar mergers. The majority of supergiants are also blue (B-type) supergiants; blue supergiants from classes O9.5 to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpha Process
The alpha process, also known as alpha capture or the alpha ladder, is one of two classes of nuclear fusion reactions by which stars convert helium into heavier elements. The other class is a cycle of reactions called the triple-alpha process, which consumes only helium, and produces carbon. The alpha process most commonly occurs in massive stars and during supernovae. Both processes are preceded by hydrogen fusion, which produces the helium that fuels both the triple-alpha process and the alpha ladder processes. After the triple-alpha process has produced enough carbon, the alpha-ladder begins and fusion reactions of increasingly heavy elements take place, in the order listed below. Each step only consumes the product of the previous reaction and helium. The later-stage reactions which are able to begin in any particular star, do so while the prior stage reactions are still under way in outer layers of the star. :\begin \ce& E=\mathsf \\ \ce& E=\mathsf \\ \ce& E=\mathsf \\ \c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
