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From space, parts of the Amazon rainforest that have previously been logged or burned may look lush and green, like a place buzzing with activity and full of sounds. But inside the rainforest the animal life may tell a different story, of a harsh environment and a quieter soundscape. Scientists from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland recorded sounds within diverse regions of the affected Amazon rainforest to better understand how the acoustics of a forest can be a cost-effective indicator of its health. Media provided by Danielle Rappaport

A study using 12 years of data from NASA’s Fermi Gamma-ray Space Telescope confirms that one supernova remnant is producing some of the highest-energy protons in our galaxy. Theorists say the highest-energy cosmic ray protons in the Milky Way reach a million billion electron volts, or petaelectronvolt (PeV) energies. But the precise nature of their sources, which astronomers call PeVatrons, has been difficult to pin down. Fermi has shown that the shock waves of exploded stars boost particles to speeds comparable to that of light. Called cosmic rays, these particles mostly take the form of protons, but can include atomic nuclei and electrons. Because they all carry an electric charge, their paths become scrambled as they whisk through our galaxy’s magnetic field, which masks their origins. But when these particles collide with interstellar gas near the supernova remnant, they produce a tell-tale glow in gamma rays — the highest-energy light there is. Out of about 300 known supernova remnants, only a few have been found to emit gamma rays at energies high enough to potentially be PeVatrons. One is G106.3+2.7, a comet-shaped cloud located about 2,600 light-years away in the constellation Cepheus. A bright pulsar caps the northern end of the supernova remnant, and astronomers think both objects formed in the same explosion. Fermi and ground-based gamma-ray observatories have detected billion- (GeV) and trillion-electron-volt (TeV) gamma rays in the tail of the remnant, away from the pulsar. By combining 12 years of Fermi observations, astronomers were able to confirm that the highest-energy gamma rays coming from the remnant must be the result of protons boosted to PeV energies — meaning that G106.3+2.7 is a PeVatron.

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