<p><strong>This supernova event likely occurred in the Upper Centaurus Lupus association, a group of massive stars approximately 457 light-years away from Earth.</strong></p>
<div class="wp-caption aligncenter" id="attachment_91850" style="width: 590px"><img alt="Illustration of an Earth-like exoplanet after X-ray radiation exposure. Image credit: NASA / CXC / M. Weiss." aria-describedby="caption-attachment-91850" class="size-full wp-image-91850" height="411" sizes="(max-width: 580px) 100vw, 580px" src="https://cdn.sci.news/images/2023/04/image_11849-X-Ray-Supernova.jpg" srcset="https://cdn.sci.news/images/2023/04/image_11849-X-Ray-Supernova.jpg 580w, https://cdn.sci.news/images/2023/04/image_11849-X-Ray-Supernova-300x213.jpg 300w, https://cdn.sci.news/images/2023/04/image_11849-X-Ray-Supernova-104x75.jpg 104w" width="580"/><p class="wp-caption-text" id="caption-attachment-91850">Illustration of an Earth-like exoplanet after X-ray radiation exposure. Image credit: NASA / CXC / M. Weiss.</p></div>
<p>Life on Earth is constantly evolving under continuous exposure to ionizing radiation from both terrestrial and cosmic origins.</p>
<p>While bedrock radioactivity slowly decreases on billion-year timescales, the levels of cosmic radiation fluctuate as our Solar System travels through the Milky Way.</p>
<p>Nearby supernova activity has the potential to raise the radiation levels at the surface of the Earth by several orders of magnitude, which is expected to have a profound impact on the evolution of life.</p>
<p>In particular, enhanced radiation levels are expected when our Solar System passes near groups of massive stars called OB associations.</p>
<p>The winds associated with these massive stellar factories are expected to initially inflate superbubbles of hot plasma, which can be the birthplaces of a large fraction of the core-collapse explosions taking place within the OB association.</p>
<p>The Solar System entered such a superbubble, commonly referred to as the Local Bubble, about 6 million years ago and currently resides near its center.</p>
<p>“The Earth entered the Local Bubble and passed through its stardust-rich exterior about 6.5 million years ago, which seeded the planet with the older iron-60, a radioactive form of iron produced by exploding stars,” said lead author Caitlyn Nojiri, an astronomer at the University of California, Santa Cruz, and colleagues.</p>
<p>“Then between 2 and 3 million years ago, one of our neighboring stars exploded with tremendous force, providing our planet with the other cohort of radioactive iron.”</p>
<p>When Nojiri and her co-authors simulated what that supernova was like, they found that it hammered the Earth with cosmic rays for 100,000 years following the blast.</p>
<p>The model perfectly explained a previously recorded spike in radiation impacting Earth around that time, which had been puzzling astronomers for years.</p>
<p>“We saw from other papers that radiation can damage DNA,” Nojiri said.</p>
<p>“That could be an accelerant for evolutionary changes or mutations in cells.”</p>
<p>Meanwhile, the authors came upon a study of virus diversity in one of Africa’s Rift Valley lakes.</p>
<p>“We can’t say that they are connected, but they have a similar timeframe,” Nojiri said.</p>
<p>“We thought it was interesting that there was an increased diversification in the viruses.”</p>
<p>The <a href="https://iopscience.iop.org/article/10.3847/2041-8213/ada27a" rel="noopener" target="_blank">study</a> was published in the <em>Astrophysical Journal Letters</em>.</p>
<p><span style="color: #808080;">_____</span></p>
<p><span style="color: #808080;">Caitlyn Nojiri <em>et al</em>. 2025. Life in the Bubble: How a Nearby Supernova Left Ephemeral Footprints on the Cosmic-Ray Spectrum and Indelible Imprints on Life. <em>ApJL</em> 979, L18; doi: 10.3847/2041-8213/ada27a</span></p>
Ionizing Radiation from Nearby Supernova Altered Virus Evolution 2.5 Million Years Ago This super...
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