- 3203 - SUPERNOVAE - new supernova discovery? Astronomers may have finally discovered convincing evidence of an elusive kind of supernova, one that could explain a bright explosion that lit up the night sky on Earth nearly 1,000 years ago and birthed the beautiful Crab Nebula.
-- ------------------- 3203 - SUPERNOVAE - new supernova discovery?
- Supernovas are giant explosions that can occur when stars die. These outbursts can briefly outshine all of the other suns in these stars' galaxies, making them visible from halfway across the universe.
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- Supernovae happen when massive stars’ gravity collects so much mass and gravity gets so strong that the atom’s electrons collapse into the protons creating neutrons. The collapse is so violent that the collapse rebounds off the core into a giant supernova explosion.
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- For decades, scientists have known of two main supernova types. Large stars more than 10 times the mass of the sun collapse in their centers when their cores burn all their fuel, causing the outer layers to explode and leaving behind a neutron star or black hole.
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- In contrast, stars less than 8 times the sun's mass burn out over time to leave a dense core of ash known as a white dwarf, and these remnants can pull fuel onto themselves off companion stars until they detonate in a thermonuclear explosion.
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- This is a different kind of supernova. These stars, around 8-10 solar masses, can explode in so-called “electron-capture supernovas“. Stars between 8 and 10 solar masses should theoretically explode in a different way.
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- Electron-capture Supernova have gigantic internal pressures that would force electrons to fuse with atomic nuclei. These electrons normally repel each other, so their removal leads to a drop in pressure inside the star. The star's core then collapses, setting off an explosion of the surrounding layers and leaving behind a neutron star slightly more massive than the sun.
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- Over decades, scientists developed predictions of what to look for in an electron-capture supernova and its progenitor star, but they had never actually confirmed a star detonating in this manner.
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- There is a thousand-year old mystery, a supernova in 1054 AD that, according to Chinese and Japanese records, was so bright it could be seen during the daytime for 23 days, and at night for nearly two years.
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- Its remnants became the “Crab Nebula“. SN 1054 was an electron-capture supernova.
SN 1054 was such a spectacular event that people recorded it around the world and preserved the records for 1,000 years.
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- Now this exploding star first detected in 2018 may be the first strong example of an electron-capture supernova. This is an important milestone in our understanding of stellar evolution and supernova physics.
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- Shortly after the supernova was discovered a research scientist at the California Institute of Technology in Pasadena, got a hold of a Hubble Space Telescope picture of the supernova.
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- After comparing this photo with archival Hubble Space Telescope images previously taken of that area of the sky, they identified the supernova's progenitor star in the galaxy NGC 2146, about 31 million light years from Earth.
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- Knowing the identity of SN 2018zd's progenitor star helped the researchers compare the star and the supernova with decades worth of electron-capture supernovas models.
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- There are six key criteria for a progenitor star of an electron-capture supernova:
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----------------- It should possess between eight and 10 solar masses. Candidates include super-asymptotic giant branch stars, that is, old bloated red giants, the widest possible stars.
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----------------- It should shed most of its mass before exploding. This shed material should mostly be in the form of helium, carbon and nitrogen, but contain little oxygen.
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- This has to do with very complicated fusion reactions during the star's life, as well as churning in the outer layers of the star, and which elements from deep in the star get dredged up to its surface. The star has a somewhat layered structure just before it explodes, with lighter elements on top of heavier ones. The heaviest oxygen layer was deeper down.
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------------------- The explosion should be relatively weak compared with other supernovas. The kinetic energy of the ejected gases is about one-tenth that of other supernovae.
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------------------- The supernova should have little radioactive fallout compared to other supernovas. For instance, when it comes to radioactive nickel, the major radioactive element that supernovas produce, electron-capture supernovas produce only about one-tenth as much radioactive nickel as a normal core-collapse supernova, and about one-hundredth as much radioactive nickel as a normal thermonuclear supernova. The progenitor should possess lots of neutron-rich elements in its core.
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- The scientists found SN 2018zd and its progenitor matched the predictions for an electron-capture supernova and its origin star. The progenitor was an old bloated red giant that had shed a significant fraction of its mass before the explosion, and the gas surrounding this star matched the expected composition. The explosion was relatively weak, produced little radioactive nickel, and possessed neutron-rich elements such as nickel within its core.
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- Electron-capture supernovas generally have long-lasting glows because their progenitor stars typically shed a lot of mass before exploding. The expanding gas from the supernova then collides with this earlier shed mass, lighting it.
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- Electron-capture supernovas also fade rapidly after a plateau lasting a few months, because they do not produce much radioactive nickel. So they are brighter than standard core-collapse supernovas at first and then fainter after a few months.
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- This is compelling support for the idea that the Crab Nebula was produced by an electron-capture supernova.
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- Your body mass is 72% material created in a supernova. Understanding how supernovae cook and spew elements into the universe helps us understand ourselves.
You really came from stars. So did everything else we know. But, we don’t know everything.
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--------------------------------- Other Reviews available:
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- 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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- 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.
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- 2636 - SUPERNOVA - 2 explosions being studied? Astronomers have detected the fallout of the biggest known explosion in the universe since it was born more than 13 billion years ago. The blast came from a supermassive black hole in the Ophiuchus galaxy cluster, located nearly 400 million light years from Earth.
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- 2149 - Supernovae from blue super giant stars. Summarizes 15 more reviews about supernovae.
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- 2299 - You are made of stardust. A Supernova is a sun, a star, that explodes because it becomes unstable after it exhaust all of its nuclear fuel. Our Sun will not become a Supernovae because it is not big enough. A bigger star will have the gravity necessary to overcome the electromagnetic force between the electron and nucleus of atoms and when its fuel is gone it goes supernova.
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- 2300 - Supernovae you can see. If you have read 2299 - “ You Were Made from Star Dust - Supernova”, you are probably anxious to learn more about Supernova. It turns out that in the last 1000 years at least six, maybe eight supernova explosions have been seen by naked eye observers.
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- 2345 - Scientists estimate it takes 100,000,000 to 200,000,000 years for intelligent life to emerge and colonize a planet. 65,000,000 years ago, at the end of the Cretaceous-Tertiary (K-T) period, 50% of life on Earth was extinguished. The dinosaurs did not survive. But, some half of marine invertebrates, plankton, marine reptiles did survive. 65,000,000 years later here we are and you are reading about it.
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- 2426 - LIFE - Exploding stars create life , and destroy life. Our galaxy is big and mostly empty space, but it harbors millions of blackholes that are remnants of supernovas and collapsing stars. When a giant star burns all it’s fuel, no heat remains to create the pressure withstanding the compression of gravity. The force of gravity collapses the stars mass into a singularity at the center of a blackhole. These creators of life are every where.
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- June 28, 2021 SUPERNOVAE - new supernova discovery? 3203
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--------------------- --- Wednesday, June 30, 2021 ---------------------------
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