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ngc 7000 - IC 5067
ngc 7635 Bubble
Cave Nebula
SH2-112
SH2-142
  SuperNova.jpg -  A supernova is an extremely strong type of stellar explosion that can outshine an entire galaxy even though visible light represents less than 1% of the energy released. It shines brightly for only a few days then fades from view over several months. During this short interval it can radiate as much energy as the Sun will emit over its entire life span. The explosion can expel much or all of the star's mass up to 10% of the speed of light driving a shock wave into the surrounding medium. This shockwave sweeps up an expanding shell of gas and dust called a supernova remnant. The shockwave can trigger the formation of new stars. There are many types of supernova. They are currently one of the hotest topics around. The primary types are triggered in one of two ways. Massive stars become supernova when they cease generating energy through nuclear fusion. White dwarf stars become supernova when they gain sufficient additional material to resume nuclear fusion.  A star with a mass at least 8x that of the Sun undergoes a core collapse type of supernova when the nuclear fusion in the star's center produces iron. All stars begin their life on the Main Sequence when gravity provides enough pressure  (sufficiently high temperature) to overcome the electron repulsion between protons at the star's center resulting in the fusion of hydrogen into helium. Eventually the hydrogen is exhausted within the core causing fusion to stop and the core to collapse which in turn heats up a shell around the core until the shell starts burning hydrogen. The core collapse and the increased area involved in fusion within the shell increases the core's temperature enough to start the fusion of helium into carbon. When the core burns helium it becomes much hotter causing the star to grow significantly larger leaving the Main Sequence becoming a red supergiant. Stars this massive take just a few million years to exhaust hydrogen in the core. The sequence of fusion of an element within the core until the element is exhausted and fusion stops, collapsing the core, triggering fusion of the element in a shell around the core increasing the temperature enough to start fusion in the core of a heavier element continues until a series on concentric shells similar to an onion are built within the star containing primarily hydrogen, helium, carbon, neon, oxygen, silicon, and finally iron at the very center. Each step requires a higher temperature and lasts for a shorter length of time. When the process produces a solid iron core, taking just a couple of  days, things change. Iron is the most stable element in the periodic table. Unlike lighter elements it will not release energy when fused so the sequence does not continue. Instead the entire star starts to collapse. The core collapses from the size of the Earth to the size of a city in a couple of seconds forcing the core's electrons and protrons together forming a very dense block of neutrons. The infalling material outside the core hits this extremely dense core at 15% of the speed of light. It bounces off producing a shockwave of tremendous energy becoming a supernova. 99% of the energy released is in the form of a 10 second burst of neutrinos. The material left after the explosion will form either a neutron star or a black hole depending on the mass of the original star. If the original star was over 130x the mass of the Sun, the star may be totally destroyed.The explosion produces all the elements in the universe heavier than iron - not through the nuclear fusion process experienced during the star's normal lifetime, but rather through another nuclear process called neutron capture which is sometimes called explosive nucleosynthesis.1 or 2 core collapse supernova are expected in a typical galaxy every 100 years, although no supernova have been observed in the Milky Way since 1604. Interestingly there have been 3 in the Whirlpool Galaxy within a span of just 17 years, all being core collapse supernova. The red supergiant star Betelgeuse will become a core collapse supernova. There are 20 known supernova remnants in the Milky Way. A type Ia supernova occurs when a white dwarf star steals enough material from an orbiting companion to allow gravity to overcome the electron pressure preventing the star from collapsing in on itself. This results in a massive burst of nuclear fusion blowing the star totally apart. The explosion is 5 billion times brighter than the Sun with little variation (an absolute magnitude of -19.3) .This uniformity allows astronomers to treat the event as a "standard candle" letting them determine the distance to the supernova and galaxy in which it resides. In 1998 two groups studying type Ia supernova in very distant galaxies announced their amazing discovery that the universe is expanding at an increasing rate. Prior to this everyone thought the rate of expansion was decreasing. We now attribute this increasing expansion to dark energy - a phenomenon we know absolutely nothing about. Type Ia supernova are much rarer than core collapse supernova, 1 or 2 occurring within a typical galaxy every 1000 years. It is possible for a white dwarf to accumulate enough material to briefly resume nuclear fusion on the star's surface without collapsing in on itself. This event is called a nova and can be repeated over time. We know of one star that has produced 6 nova in the last 100 years. It causes the star to significantly brighten but is much dimmer than a supernova. It's believed that the Milky Way experiences roughly 40 nova each year.  
M01 Crab
M51 with supernova
M82 with supernova
M95 with supernova
Veil

A supernova is an extremely strong type of stellar explosion that can outshine an entire galaxy even though visible light represents less than 1% of the energy released. It shines brightly for only a few days then fades from view over several months. During this short interval it can radiate as much energy as the Sun will emit over its entire life span. The explosion can expel much or all of the star's mass up to 10% of the speed of light driving a shock wave into the surrounding medium. This shockwave sweeps up an expanding shell of gas and dust called a supernova remnant. The shockwave can trigger the formation of new stars.

There are many types of supernova. They are currently one of the hotest topics around. The primary types are triggered in one of two ways. Massive stars become supernova when they cease generating energy through nuclear fusion. White dwarf stars become supernova when they gain sufficient additional material to resume nuclear fusion.

A star with a mass at least 8x that of the Sun undergoes a core collapse type of supernova when the nuclear fusion in the star's center produces iron. All stars begin their life on the Main Sequence when gravity provides enough pressure (sufficiently high temperature) to overcome the electron repulsion between protons at the star's center resulting in the fusion of hydrogen into helium. Eventually the hydrogen is exhausted within the core causing fusion to stop and the core to collapse which in turn heats up a shell around the core until the shell starts burning hydrogen. The core collapse and the increased area involved in fusion within the shell increases the core's temperature enough to start the fusion of helium into carbon. When the core burns helium it becomes much hotter causing the star to grow significantly larger leaving the Main Sequence becoming a red supergiant. Stars this massive take just a few million years to exhaust hydrogen in the core. The sequence of fusion of an element within the core until the element is exhausted and fusion stops, collapsing the core, triggering fusion of the element in a shell around the core increasing the temperature enough to start fusion in the core of a heavier element continues until a series on concentric shells similar to an onion are built within the star containing primarily hydrogen, helium, carbon, neon, oxygen, silicon, and finally iron at the very center. Each step requires a higher temperature and lasts for a shorter length of time. When the process produces a solid iron core, taking just a couple of days, things change. Iron is the most stable element in the periodic table. Unlike lighter elements it will not release energy when fused so the sequence does not continue. Instead the entire star starts to collapse. The core collapses from the size of the Earth to the size of a city in a couple of seconds forcing the core's electrons and protrons together forming a very dense block of neutrons. The infalling material outside the core hits this extremely dense core at 15% of the speed of light. It bounces off producing a shockwave of tremendous energy becoming a supernova. 99% of the energy released is in the form of a 10 second burst of neutrinos. The material left after the explosion will form either a neutron star or a black hole depending on the mass of the original star. If the original star was over 130x the mass of the Sun, the star may be totally destroyed. The explosion produces all the elements in the universe heavier than iron - not through the nuclear fusion process experienced during the star's normal lifetime, but rather through another nuclear process called neutron capture which is sometimes called explosive nucleosynthesis. 1 or 2 core collapse supernova are expected in a typical galaxy every 100 years, although no supernova have been observed in the Milky Way since 1604. Interestingly there have been 3 in the Whirlpool Galaxy within a span of just 17 years, all being core collapse supernova. The red supergiant star Betelgeuse will become a core collapse supernova. There are 20 known supernova remnants in the Milky Way.

A type Ia supernova occurs when a white dwarf star steals enough material from an orbiting companion to allow gravity to overcome the electron pressure preventing the star from collapsing in on itself. This results in a massive burst of nuclear fusion blowing the star totally apart. The explosion is 5 billion times brighter than the Sun with little variation (an absolute magnitude of -19.3). This uniformity allows astronomers to treat the event as a "standard candle" letting them determine the distance to the supernova and galaxy in which it resides. In 1998 two groups studying type Ia supernova in very distant galaxies announced their amazing discovery that the universe is expanding at an increasing rate. Prior to this everyone thought the rate of expansion was decreasing. We now attribute this increasing expansion to dark energy - a phenomenon we know absolutely nothing about. Type Ia supernova are much rarer than core collapse supernova, 1 or 2 occurring within a typical galaxy every 1000 years. It is possible for a white dwarf to accumulate enough material to briefly resume nuclear fusion on the star's surface without collapsing in on itself. This event is called a nova and can be repeated over time. We know of one star that has produced 6 nova in the last 100 years. It causes the star to significantly brighten but is much dimmer than a supernova. It's believed that the Milky Way experiences roughly 40 nova each year.

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