- 3708 - - STARS - dust plumes and supernovae? Cosmic explosions that blast out stellar remains at near the speed of light, leaving a black hole behind, are physics occurring in the most extreme environments that are impossible to recreate on Earth.
--------------------- 3708 - STARS - dust plumes and supernovae?
- The James Webb Space telescope has captured an image of intense light from a star pushing multiple dust plumes into space, October, 2022. The propulsive effect of the starlight is “radiation pressure“. Radiation pressure is one of the factors preventing stars from collapsing under their own gravity and creates the bright smudged tails of comets as they pass close to the sun.
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- A pair of stars in “WR140“, located 5,600 light-years away in the Cygnus constellation is a binary star system is encircled by an onion-like shell of almost 20 concentric ripples.
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- The ripples are great plumes of glowing dust and soot spewed out as a pair of leaky stars in WR140 swing closely past each other in an elliptical orbit that they complete roughly every eight years.
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- As the two approach, their 1,864 miles per second, ( 6,710,400 miles per hour ), solar winds smash into each other, arcing a plume of material across space that slowly expands to form rings. As the plumes are only ejected when the stars are near each other, the spacing of the rings is set by their orbital period. This means the dust is made in regular intervals, and the cloud's rings can be counted like tree rings to find the age of the outermost ripple, with 20 visible rings amounting to 160 years of dust.
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- These ripples are not expanding outwards at a constant speed. Rather, they are accelerating, pushed on by periodic blast of photons, or light particles, from the stars nearby. It is this acceleration that changes the spacing of the gaps between the rings.
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- One of the stars is a ‘Wolf-Rayet star‘, a type of rare, slowly-dying star that has lost its outer shell of hydrogen, leaving it to spew out ghosts of ionized helium, carbon and nitrogen from its insides. These stars will explode as supernovas one day, but until then the radiation pressure produced by the light unfurls their burst contents, stretching them out like giant phantom jellyfish in the night sky. Ejected superheated elements, especially the carbon that is transformed into soot, stay hot enough to glow bright in the infrared spectrum.
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- The other member of the pair is an ‘O-type blue super giant star“ , one of the most massive classes of stars. Hot, bright, and enormous, the supergiant is also leaking gas and destined to supernova. When the two stars fly close to each other, their solar winds are combined into a giant cone of material which is shot out into space.
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- The star puffs out sculpted smoke rings every eight years. Eight years later as the binary returns in its orbit, another appears the same as the one before, streaming out into space inside the bubble of the previous one. The highly predictable timings of the puffs and their expansion over large distances gave the astronomers a unique opportunity to study the underlying physics of the ejections.
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- The Keck Observatory infrared camera tracked the glowing rings as they were pushed outwards and slowly grew over the course of 16 years. The James Webb space telescope showed all twenty rings in crystal clear definition.
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- In the absence of external forces, each dust spiral should expand at a constant speed.
However, the dust rings were accelerating due to periodic shoves from starlight, which, like all light, carries momentum. Starlight's radiation pressure has never been directly measured observed acting on dust before now. This is because close to stars, where the radiation pressure is strongest, the shoves it produces are often masked by extremely powerful gravitational and magnetic fields.
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- The James Webb Space Telescope revealed these concentric angular rings around the giant, distant star in September, 2022. Wolf-Rayet stars represent the final stage in the evolution of giant stars, dozens of times more massive than the sun, before they explode in supernovas and turn into Blackholes.
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- The other star in the WR140 system is less bright a giant star just shy of Wolf Rayet size, at about 20 times the size of the sun. The interaction of these two enormous stars triggers cosmic fireworks that give rise to the oddly shaped concentric rings that these.
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- The James Webb Space Telescope's measurement also revealed that the dust these stars produce contains organic, carbon-rich grains, the same type of particles that are the building blocks of life on Earth. For Webb, this is just the beginning. The astronomers expect more ground-breaking discoveries about WR140 in the months and years to come.
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- When a massive star approaches the end of its life, it goes through several violent phases. Deep in the star's core, it shifts from fusing hydrogen to fusing heavier elements, starting with helium and moving up to carbon, oxygen, magnesium and silicon. At the end of the chain, the star eventually forms iron in its core. Because iron saps energy rather than releasing it, this spells the end for the star, and in less than a dozen minutes, it turns itself inside out in a fantastic explosion called a “supernova“.
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- The most famous example of such a near-terminal star is ‘Betelgeuse“. If it were placed within our solar system, this star, which is only 11 times more massive than the sun, would stretch to the orbit of Jupiter. It will go supernova any day now, but "any day" for an astronomer could be a million years away. Even though we know that these kinds of stars will eventually detonate in a supernova, there's no way to get a more precise estimate than that.
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- The stars that result in these kinds of supernovas are thought to have dense shrouds of material surrounding them before they explode. These shrouds are orders of magnitude denser than what's measured around Betelgeuse. It's the heating of that material from the initial shock wave that causes the brightness to linger; there's simply more stuff lying around to keep glowing well after the first sign of the explosion.
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- When the explosion initially happens, the shock wave hits the material around the star, which causes the shock wave to lose steam as it passes through. While initially the energies from a supernova are enough to release high-energy radiation, like X-rays and gamma-rays, after the mixing of the shock wave and the surrounding material, the radiation given off is in optical wavelengths. These dense shrouds of material around the stars are also a giveaway that a supernova is about to happen.
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- Once a supergiant star builds a thick shroud of material around itself, it is likely to go supernova within a few years. Considered yourself warned. Astronomers just detected what may be the most powerful flash of light ever seen. The so-called gamma-ray burst, the most energetic type of electromagnetic explosion known to exist in the universe, was first spotted by telescopes October 9, 2022.
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- Gamma-ray bursts are produced when giant stars explode at the ends of their lives before collapsing into black holes, or when ultradense stellar remnants known as neutron stars collide. Within seconds, these explosions unleash as much energy as the sun will emit during its entire 10-billion-year lifetime.
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- The flash detected was the strongest one ever observed, releasing 18 tera-electronvolts of energy. Analyses of the signal confirmed that it was indeed a gamma-ray burst coming from a source some 2.4 billion light-years away.
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- Although this gamma-ray burst was within a safe distance from Earth, a much closer one would be catastrophic to our planet. Such an energetic flash within thousands of light-years from Earth would strip the planet of its protective ozone layer and likely cause mass extinction. In fact, scientists think one of the biggest mass-extinction events in Earth's history, the Ordovician extinction, which occurred 450 million years ago, may have been triggered by such a blast.
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- Gamma-ray bursts come in two varieties. Short gamma-ray bursts are rarer and last no longer than two seconds. These bursts make up about 30% of all such events and are believed to be caused by collisions of neutron stars.
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- The other type, long gamma-ray bursts, can last up to several minutes and are likely produced by hypernovas, stellar explosions that are 100 times brighter than supernovas, in which supermassive stars die after running out of the hydrogen fuel in their cores.
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- Astronomers mostly see the afterglow of these explosions that comes from electrons energized by the blast. Telescopes all over the world and in Earth's orbit are now pointing at the dusty galaxy from which the flash emerged. They will try to observe the light generated by the explosion in as many wavelengths as possible to get the most complete picture of its origin.
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- Cosmic explosions that blast out stellar remains at near the speed of light, leaving a black hole behind, are physics occurring in the most extreme environments that are impossible to recreate on Earth.
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October 15, 2022 STARS - dust plumes and supernovae? 3708
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