According to data collected from a number of orbiting space X-ray telescopes, astronomers now believe that the lethal zone for nearby habitable planets when a supernova explodes is much larger than previously thought, as great as almost 200 light years.
The calculations in this latest study are based on X-ray observations of 31 supernovae and their aftermath mostly obtained from Chandra, NASA’s Swift and NuSTAR missions, and ESA’s (European Space Agency’s) XMM-Newton. The analysis of these observations shows that there can be lethal consequences from supernovae interacting with their surroundings, for planets located as much as about 160 light-years away. “If a torrent of X-rays sweeps over a nearby planet, the radiation would severely alter the planet’s atmospheric chemistry,” said Ian Brunton of the University of Illinois at Urbana-Champaign who led the study. “For an Earth-like planet, this process could wipe out a significant portion of ozone, which ultimately protects life from the dangerous ultraviolet radiation of its host star.”
You can read the paper here [pdf], which includes a figure that suggests in certain circumstances the lethal zone can be 200 light years across. As the scientists note:
Perhaps the most interesting results are the distances at which the X-ray emission can impose lethal effects on an Earth-like biosphere. This larger range of influence has consequences for the Galactic habitable zone, such as the harmful implications for recently discovered exoplanets that would be susceptible to nearby [supernovae].
In other words, this data suggests the galaxy is far less hospitable to the development of life. It takes a lot of time for life to evolve, billions of years, and during that time a solar system traveling through the galaxy has now a much higher chance of passing too close to a supernova explosion.
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