- 3747 - STARDUST - from distant supernovae? The quest to study cosmic dust samples brought to Earth by meteorites has been ongoing for the past 30 years. But this study marks the first time that scientists were able to distinguish components of the dust that were created by supernova explosions.
--------------------- 3747 - STARDUST - from distant supernovae?
- Astronomers have discovered a new population of stardust that originated from supernovas. This suggests that more interstellar dust formed from these massive star explosions than scientists previously thought.
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- Using a “nanoscale imaging spectrometer”, called “Cameca NanoSIMS 50L“, researchers were able to measure the chemical composition of tiny grains of stardust by observing them with unprecedented resolution. The researchers analyzed the chemical makeup of several grains of stardust, drawing conclusions about the cosmic origins of those grains.
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- Testing for nucleosynthesis determines how new atoms are formed by red giant stars; these are dying stars in their last stages of stellar evolution. The dust that formed our solar system 4.6 billion years ago contains a small but important fraction (about 1%) more supernova dust than anticipated.
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- Did supernova contribute to the origins of our solar system? Astronomers need to learn how much dust comes from the stars, how much comes from supernovas, or, how much forms near the interstellar medium.
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- By studying the dust up close, they could measure the levels of magnesium found in these presolar dust grains, or grains that originated before the sun existed. The results showed that a fraction of the dust could not have been formed by red giant stars and, therefore, must have come from supernova explosions instead.
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- This study reinforces the notion that “we are all made of stardust“, or rather our atoms all came from materials in stars. There was an earlier idea that all of that stardust had come from supernova. However, that idea was later proved wrong. 90% of presolar grains came from lower-mass stars that don't turn to supernova stars.
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- Stars that explode may be producing more planet-forming elements than we expected. The material that makes up the solar system, save for hydrogen and helium, has to come from these stars.
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- This higher-than-expected percentage of supernova dust can help scientists interpret the heavy-element composition of the solar system.
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- Particle accelerators are used to simulate this element creation. But, cosmic rays launch particles with energy 10 times greater than the “Large Hadron Collider“.
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- Some space radiation crashing into Earth has this type of explosive origin. Astronomers have spotted wreckage from a supernova explosion potentially capable of blasting out high-energy particles, cosmic rays, that frequently bombard Earth.
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- Their new findings link shockwaves and wreckage created by dying stars to natural high-energy proton accelerators in space, which are called “PeVatrons“. These intriguing cosmic accelerators which receive their name from their ability to boost the energies of particles to extreme peta-electronvolt (PeV) levels have never been identified.
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- A handful of suspected PeVatrons were already fingerprinted before this study, including one at the center of our Milky Way galaxy. The research team says their new find of a supernova explosion's leftovers, a cloud of material called “G106.3+2.7“, could be the most promising candidate yet.
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- The wreckage lurks 2,600 light-years from Earth, possesses a comet-shape and has a bright pulsar, a highly magnetic rotating neutron star, at one end. Because neutron stars form when stars undergo gravitational collapse, which also launches out supernovas, there is good reason for researchers to think that the pulsar and the supernova wreckage cloud were created by the same violent event.
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- Using NASA's “Fermi Large Area Telescope“, astronomers spotted a high-energy gamma-ray afterglow that implies G106.3+2.7 may be capable of the PeVatron-associated feat of blasting out particles at energies equivalent to a million billion electron volts , 10 times as great as energies generated by the Large Hadron Collider, Earth's most powerful particle accelerator.
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- Theorists think the highest-energy cosmic ray protons in the Milky Way reach a million billion electron volts or PeV energies. They suspect the supernova wreckage from dead stars accelerates particles to such high energies when charged particles are ensnared by magnetic fields around them.
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- This process allows shockwaves from the supernova to buffet the trapped particles repeatedly, increasing their energy each time. Finally, the particles are so energetic that the supernova remains cannot hold on to them, and the particles escape into space at near-light-speeds as “cosmic rays“, which are actually particles not just “rays“.
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- Tracing cosmic rays back to supernova wreckage has been difficult because the proton particles that comprise cosmic rays are electrically charged. Cosmic rays are thus prone to scattering while interacting with magnetic fields as they journey through space. Astronomers, therefore, cannot easily tell from which direction the rays are coming when they finally reach our planet.
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- Because the acceleration of protons to such high speeds causes the emission of gamma-rays, however, this high-energy light could be a good proxy for detecting the source of cosmic rays.
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- Gamma-rays from inside the tail of the supernova wreckage of G106.3+2.7 were detected. Observatories have found extremely high-energy photons coming from the same area, indicating this could indeed be a PeVatron.
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- However, the catch is that electrons accelerated to a few hundred TeV can produce the same emission.
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- To analyze gamma-rays from the comet-shaped cloud, the astronomers had to first account for the pulsar , J2229+6114 , emitting its own gamma-rays as it rapidly rotates. Because the high-energy light is only blasted towards Earth during half of the pulsar’s rotational period, the researchers simply ignored gamma-ray emissions during this period.
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- The tail of G106.3+2.7 appears to emit few gamma-ray photons with energies below 10 Giga-electronvolts (GeV); above this benchmark, the pulsar’s effect was tiny. The lack of gamma-rays below 10 GeV also indicated the detected emissions were not caused by the accelerating electrons.
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- This finding led the researchers to infer that the source of some gamma-rays from G106.3+2.7 was indeed the acceleration of protons to PeV-level energies. So far, G106.3+2.7 is unique, but it may turn out to be the brightest member of a new population of supernova remnants that emit gamma rays reaching TeV energies.
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November 18, 2022 STARDUST - from distant supernovae? 3747
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