New research shows that some supernovae are more powerful than thought. And nearby supernovae may have driven evolution.
showed up to 20 supernovae in the last 11 million years in the Scorpius-Centaurus OB association. Some of these were as close as 130 light-years to Earth. The paper’s authors say that about 2 million years ago, one of the supernovae exploded close enough to our planet to damage the ozone layer.
In a scenario where an SN exploded close to Earth, it can take months or years following the initial explosion for the x-rays to arrive. Interactions with the circumstellar debris cause a delay. The x-rays can deplete Earth’s ozone layer, allowing harmful UV radiation from the Sun to reach the planet’s surface.
Researchers aren’t sure about the lethal distances of supernovae. There are many variables, both in the progenitor star and its environment. The progenitor star’s mass loss is especially important. But by characterizing the lethal x-ray dose for Earth’s stratosphere and the energy output of some of the brightest SN, the authors calculated the lethal distance for some well-known supernovae.exploded in the Large Magellanic Cloud, and the light reached Earth in 1987.
Type IIn supernovae also have the greatest range of influence. This shows that these SN could significantly influence Earth’s biosphere from greater distances. Advances in x-ray astronomy will shed more light on the consequences for terrestrial planets, and the authors think there’s lots more to uncover. But their observations show that “… the interacting X-ray phase of an SN’s evolution can entail significant consequences for terrestrial planets.
Ionizing radiation from supernovae can alter Earth’s atmospheric chemistry from substantial distances. The initial burst of energy from an SN poses one threat, and so do the cosmic rays that arrive hundreds or thousands of years later and linger. But this research adds another threat: x-rays that arrive months or years after the initial outburst.
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