- 3186 - SUPERNOVA - is what we are made of? Always, somewhere in the universe a star is reaching the end of its life. If it is a massive star it collapsing under its own gravity and becomes a supernovae. If it is much smaller it collapses into a dense cinder of a star, stealing matter from a companion star until it can’t handle its own mass and it goes supernovae.
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- Supernovae explode leaving us with unparalleled brightness and a tsunami of atomic particles and chemical elements of which we are made of.
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- The oldest recorded supernova dates back almost 2000 years. In 185 AD, Chinese astronomers noticed a bright light in the sky. Documenting their observations in the “Book of Later Han“, these ancient astronomers noted that it sparkled like a star, appeared to be half the size of a bamboo mat and did not travel through the sky like a comet.
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- Over the next eight months this celestial visitor slowly faded from sight. They called it a “guest star.”
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- 2000 years later, in the 1960s, scientists found hints of this mysterious visitor in the remnants of a supernova approximately 8,000 light-years away. This supernova, SN 185, is the oldest known supernova recorded by humankind.
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- Many of the elements we are made of come from these supernovae. Everything from the oxygen you’re breathing to the calcium in your bones, the iron in your blood and the silicon in your computer was brewed up in the heart of a star that goes supernova.
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- As a supernova explodes, it unleashes a hurricane of nuclear reactions. These nuclear reactions produce many of the building blocks of the world around us. Most all of elements between oxygen and iron comes from core-collapse supernovae, those massive stars that collapse under their own gravity.
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- These explosions are responsible for producing the universe’s elements up to iron within thermonuclear supernovae. They become white dwarf stars that steal mass from their binary companions. These supernovae that they become are responsible for the production of most of the elements heavier than iron.
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- Supernovae are also neutrino factories. In a 10-second period, a core-collapse supernova will release a burst of more than 10^58 neutrinos. Neutrinos are almost weightless particles that can travel undisturbed through almost everything in the universe. (See separate reviews about these mysterious neutrinos)
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- Outside of the core of a supernova, it would take a light-year of lead to stop a neutrino. But when a star explodes, the center can become so dense that even neutrinos take a little while to escape. When they do escape, these neutrinos carry away 99 percent of the energy generated by the supernova explosion.
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- Supernovae are powerful particle accelerators. They are natural space laboratories. They can accelerate particles to at least 1000 times the energy of particles in the Large Hadron Collider, the most powerful collider we have on Earth.
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- The interaction between the blast of a supernova and the surrounding interstellar gas creates a magnetized region, called a shock. As particles move into the shock, they bounce around the magnetic field and get accelerated.
- When they are released into space, some of these high-energy particles, called “cosmic rays“ They eventually slam into our atmosphere, colliding with atoms and creating showers of secondary particles that rain down on our heads. You probably did not notice that.
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- Supernovae produce radioactivity. They are forging elements and neutrinos, the nuclear reactions inside of supernovae also cook up radioactive isotopes. Some of this radioactivity emits light signals, such as “gamma rays“, that we can see in space.
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- This radioactive gamma rays are part of what makes supernovae so bright. It also provides us with a way to determine if any supernovae have blown up near Earth. If a supernova occurred close enough to our planet, we would have sprayed the Earth with some of these unstable nuclei.
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- When scientists come across layers of sediment with spikes of radioactive isotopes, they know to investigate whether what they’ve found was spit out by an exploding star.
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- In 1998, physicists analyzed crusts from the bottom of the ocean and found layers with a surge of 60Fe, a rare radioactive isotope of iron that can be created in copious amounts inside supernovae.
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- Using the rate at which 60Fe decays over time, they were able to calculate how long ago it landed on Earth. They determined that it was most likely dumped on our planet by a nearby supernova about 2.8 million years ago.
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- A nearby supernova could cause a mass extinction. If a supernova occurred close enough, it could be pretty bad news for our planet. Although we’re still not sure about all the ways being in the midst of an exploding star would affect us, we do know that supernovae emit truckloads of high-energy photons such as X-rays and gamma rays.
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- The incoming radiation would strip our atmosphere of its ozone. All of the critters in our food chain from the bottom up would fry in the sun’s ultraviolet rays until there was nothing left on our planet but dirt and the bones of disgruntled scientists.
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- Supernovae occur in our galaxy at a rate of about one or two per century. We have not seen a supernova in the Milky Way in around 400 years. The most recent nearby supernova was observed in 1987, and it wasn’t in our galaxy. It was in a nearby satellite galaxy called the Large Magellanic Cloud.
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- “IK Pegasi“ , the closest candidate star we have identified for a supernova, is 150 light-years away, too far to do any real damage to Earth.
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- Even that 2.8-million-year-old supernova that ejected its radioactive insides into our oceans was at least 100 light-years from Earth. It was not close enough to cause a mass-extinction. The physicists deemed it a “near miss.”
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- Supernovae light can echo through time. Just as your voice echoes when its sound waves bounce off a surface and come back again, a supernova echoes in space when its light waves bounce off cosmic dust clouds and redirect themselves toward Earth.
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- Because the echoed light takes an extensive route to our planet, this phenomenon opens a portal to the past, allowing scientists to look at and decode supernovae that occurred hundreds of years ago.
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- A recent example of this is SN1572, “Tycho’s supernova“, a supernova that occurred in 1572. This supernova shined brighter than Venus, was visible in daylight and took two years to dim from the sky.
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- A most recent discovery is an exploding white dwarf star that blasted itself out of its orbit with another star in a ‘partial supernova’ and is now hurtling across our galaxy. It opens up the possibility of many more survivors of supernovae traveling undiscovered through the Milky Way, as well as other types of supernovae occurring in other galaxies that astronomers have never seen before.
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- Reported on July 15, 2020 was a white dwarf that was previously found to have an unusual atmospheric composition. It reveals that the star was most likely a binary star that survived its supernova explosion, which sent it and its companion flying through the Milky Way in opposite directions.
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- White dwarfs are the remaining cores of red giant stars after these huge stars have died and shed their outer layers, cooling over the course of billions of years. The majority of white dwarfs have atmospheres composed almost entirely of hydrogen or helium, with occasional evidence of carbon or oxygen dredged up from the star’s core.
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- This star, (SDSS J1240+6710), seemed to contain neither hydrogen nor helium, composed instead of an unusual mix of oxygen, neon, magnesium, and silicon. Using the Hubble Space Telescope, the scientists also identified carbon, sodium, and aluminum in the star’s atmosphere, all of which are produced in the first thermonuclear reactions of a supernova.
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- However, there is a clear absence of what is known as the ‘iron group’ of elements, iron, nickel, chromium, and manganese. These heavier elements are normally cooked up from the lighter ones, and make up the defining features of thermonuclear supernovae. The lack of iron group elements in this star suggests that the star only went through a partial supernova before the nuclear burning died out.
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- The scientists were able to measure the white dwarf’s velocity and found that it is traveling at 900,000 kilometers per hour. (560,000 miles per hour). It also has a particularly low mass for a white dwarf, only 40% the mass of our Sun, which would be consistent with the loss of mass from a partial supernova.
- This star has a chemical composition which is the fingerprint of nuclear burning, a low mass and a very high velocity: all of these facts imply that it must have come from some kind of close binary system and it must have undergone thermonuclear ignition. It would have been a type of supernova, but of a kind that we haven’t seen before.
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- The scientists theorize that the supernova disrupted the white dwarf’s orbit with its partner star when it very abruptly ejected a large proportion of its mass. Both stars would have been carried off in opposite directions at their orbital velocities . That sling shot effect would account for the star’s high velocity.
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- The best-studied thermonuclear supernovae are the “Type 1a,” which led to the discovery of dark energy, and are now routinely used to map the structure of the Universe. But there is growing evidence that thermonuclear supernovae can happen under very different conditions.
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- Without the radioactive nickel that powers the long-lasting afterglow of the Type 1a supernovae, the explosion that sent this star hurtling across our Milky Way Galaxy would have been a brief flash of light that would have been difficult to discover.
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- Astronomers are discovering that there are different types of white dwarf that survive supernovae under different conditions and using the compositions, masses and velocities that they have, we can figure out what type of supernova they have undergone.
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- There is clearly a whole zoo out there. Studying the survivors of supernovae in our Milky Way will help us to understand the myriads of supernovae that we see going off in other galaxies. The fact that such a low mass white dwarf went through carbon burning is a testimony of the effects of interacting binary evolution and its effect on the chemical evolution of the Universe.”
- In 2008, astronomers found light waves originating from the cosmic demolition site of the original star. They determined that they were seeing light echoes from Tycho’s supernova. Although the light was 20 billion times fainter than what astronomer Tycho Brahe observed in 1572, scientists were able to analyze its spectrum and classify the supernova as a thermonuclear supernova.
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- More than four centuries after its explosion, light from this historical supernova is still arriving at Earth.
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- Supernovae were used to discover “dark energy“. Because thermonuclear supernovae are so bright, and because their light brightens and dims in a predictable way, they can be used as lighthouses for cosmology.
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- In 1998, scientists thought that cosmic expansion, initiated by the big bang, was likely slowing down over time. But supernova studies suggested that the expansion of the universe was actually speeding up.
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- Scientists can measure the true brightness of supernovae by looking at the timescale over which they brighten and fade. By comparing how bright these supernovae appear with how bright they actually are, scientists are able to determine how far away they are.
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- Scientists can also measure the increase in the wavelength of a supernova’s light as it moves farther and farther away from us. This is called the “redshift“, wavelengths stretch out as light travels through an expanding universe.
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- Comparing the redshift with the distances of supernovae allowed scientists to infer how the rate of expansion has changed over the history of the universe. Scientists believe that the culprit for this cosmic acceleration is something called “dark energy“.
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- Supernovae occur at a rate of approximately 10 per second. By the time you reach the end of this sentence, it is likely a star will have exploded somewhere in the universe.
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- As scientists evolve better techniques to explore space, the number of supernovae they discover increases. Currently they are finding over a thousand supernovae per year.
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- But when you look deep into the night sky at bright lights shining from billions of light-years away, you’re actually looking into the past. The supernovae that scientists are detecting stretch back to the very beginning of the universe.
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- By adding up all of the supernovae they’ve observed, scientists can figure out the rate at which supernovae occur across the entire universe. Scientists estimate about 10 supernovae occur per second, exploding in space like popcorn in the microwave.
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- We are about to get much better at detecting far-away supernovae. Even though we’ve been aware of these exploding stars for millennia, there’s still so much we don’t know about them. There are two known types of supernovae, but there are many different varieties that scientists are still learning about.
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- Supernovae could result from the merger of two white dwarfs. Alternatively, the rotation of a star could create a blackhole that accretes material and launches a jet through the star. Or the density of a star’s core could be so high that it starts creating electron-positron pairs, causing a chain reaction in the star.
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- Today we are mapping the night sky with the “Dark Energy Survey“, or DES. Scientists can discover new supernova explosions by looking for changes in the images they take over time.
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- Another survey currently going on is the All-Sky Automated Survey for Supernovae, ASAS-SN, which recently observed the most luminous supernova ever discovered.
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- In 2019, the “Large Synoptic Survey Telescope“, or LSST, will revolutionize our understanding of supernovae. LSST is designed to collect more light and peer deeper into space than ever before. It will move rapidly across the sky and take more images in larger chunks than previous surveys. This will increase the number of supernovae we see by hundreds of thousands per year.
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- Studying these supernovae will expand our knowledge of space and bring us even closer to understanding not just our origin, but the cosmic reach of the universe.
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-------------------------------------- Other reviews available:
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- 3160 - SUPERNOVAE - are what we are made of! Supernovae, stars that explode when they can no longer continue fusion radiation, are rare events. In the Observable Universe the event happens every second. We are living in and made of star dust and gas. When you look at the night sky and see those stars say “ that is where I came from”.
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- 3159 - SUPERNOVA - why do stars explode? Astronomers have problems explaining how the supernova explosion actually occurs. A theory is that the explosion happens because of sound waves? That is what computer simulations are telling astronomers today. All the math remains to be worked out, but, computer simulations are getting closer to the observations they see in supernova explosions.
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- 3013 - SUPERNOVA - one explosion nearby? At that same time, there was also an extinction event on Earth, called the “Pliocene marine mega fauna” extinction. Up to a third of the large marine species on Earth were wiped out at the time, most of them living in shallow coastal waters.
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- 2997 - SUPERNOVA - gold forged in exploding stars? - Astronomers are winding back the clock on the expanding remains of a nearby, exploded star. By using our Hubble Space Telescope, they retraced the speedy shrapnel from the blast to calculate a more accurate estimate of the location and time of the exploding star.
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- 2650 - SUPERNOVAE - are what we are made of! - Supernovae, stars that explode when they can no longer continue fusion radiation, are rare events. They are likely to happen only once per year in our Milky Way Galaxy. But, in the Observable Universe the event happens every second.
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- 2649 - SUPERNOVA - the runaway universe? Nuclear fusion will occur when a star’s central temperature reaches 10,000,000 degrees. The collisions of the atoms are so rapid at that temperature that all electrons are stripped away from their nucleus. And, nuclei collide to such an extent as to overcome the repulsive electric force of their mutual positive charges.
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- 2648 - SUPERNOVA - what is the youngest? A supernova normally goes off in a galaxy every 50 to 100 years. However, we have not seen one in several hundred years. It could be that they are going off and they are out of sight. The last one astronomers had recorded for the Milky Way is Cassiopeia A. It went supernova 330 years ago, that would be in 1678.
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- 2646 - SUPERNOVAE - how life is being created? Betelgeuse is still deep in the red supergiant phase of its life. Even though it has dimmed significantly of recent, it isn’t on the verge of exploding.
- June 8, 2021 SUPERNOVA - is what we are made of? 3186
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--------------------- --- Tuesday, June 8, 2021 ---------------------------
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