- 3780 - STARDUST - is what you are made of. Science has known “humans are made of stardust“ for some time, and now, a new survey of 150,000 stars shows just how true the old cliché is: Humans and their galaxy have about 97 percent of the same kind of atoms, and the elements of life appear to be more prevalent toward the galaxy's center.
--------------------- 3780 - STARDUST - is what you are made of.
- The crucial elements for life on Earth, often called the building blocks of life are carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. For the first time, astronomers have cataloged the abundance of these elements in a huge sample of stars.
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- The astronomers evaluated each element's abundance through “spectroscopy“; each element emits distinct wavelengths of light from within a star, and they measured the depth of the dark and bright patches in each star's light spectrum to determine what it was made of.
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- The researchers used stellar measurements from the Sloan Digital Sky Survey's (SDSS) Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectrograph in New Mexico. APOGEE can peer through the dust in the Milky Way because it uses infrared wavelengths, which pass through dust.
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- This instrument collects light in the near-infrared part of the electromagnetic spectrum and disperses it, like a prism, to reveal signatures of different elements in the atmospheres of stars.
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- A fraction of the almost 200,000 stars surveyed by APOGEE overlap with the sample of stars targeted by the NASA Kepler mission, which was designed to find potentially Earth-like planets.
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- Although humans share most elements with the stars, the proportions of those elements differ between humans and stars. For example, humans are about 65 percent oxygen by mass, whereas oxygen makes up less than 1 percent of all elements measured in the spectra of stars.
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- The six most common elements of life on Earth (including more than 97 percent of the mass of a human body) are carbon, hydrogen, nitrogen, oxygen, sulphur and phosphorus. Those same elements are abundant at the center of our Milky Way galaxy.
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- The proportion of each element of life differed depending on the region of the galaxy in which it was found. The sun resides on the outskirts of one of the Milky Way's spiral arms. Stars on the outskirts of the galaxy have fewer heavy elements required for life's building blocks, such as oxygen, than those in more central regions of the galaxy.
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- We are now able to map the abundance of all of the major elements found in the human body across hundreds of thousands of stars in our Milky Way. This allows us to place constraints on when and where in our galaxy life had the required elements to evolve, a sort of 'temporal galactic habitable zone.'"
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- Some of the space radiation crashing into Earth has an explosive origin. This is the wreckage from supernova explosions potentially capable of blasting out high-energy particles, cosmic rays, that frequently bombard Earth.
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- New findings link shockwaves and wreckage created by dying stars to natural high-energy proton accelerators in space, 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 conclusively identified.
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- A handful of suspected PeVatrons were already fingerprinted including one at the center of our Milky Way galaxy. The astronomers have found a supernova explosion's leftovers, a cloud of material called “G106.3+2.7“.
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- The cloud lurks 2,600 light-years from Earth, possesses a comet-shape and has a bright pulsar , which is 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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- Scientists suspect the supernova wreckage from dead stars accelerates particles to such high energies when charged particles are ensnared by magnetic fields around them. 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.
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- Tracing cosmic rays back to supernova wreckage has been difficult because the protons that comprise cosmic rays are electrically charged. Cosmic rays are therefore prone to scattering while interacting with magnetic fields as they journey through space. Astronomers 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 this high-energy light could be a good proxy for detecting the source of cosmic rays.
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- To analyze gamma-rays from the comet-shaped cloud, the team had to first account for the pulsar 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. This infers that the source of some gamma-rays from G106.3+2.7 was indeed the acceleration of protons to PeV-level energies.
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December 12, 2022 STARDUST - is what you are made of. 3780
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