Supernovas – are they good for the Earth? Well, over 4.5 billion years ago, one or more of them or neutron star mergers got the Earth going! They created all the chemical elements heavier than lithium, the bases of life and of the solid Earth. But now, another supernova close to Earth could pretty well sterilize the Earth of living organisms with intense radiation and more.
So, what are the odds of a close one? And by close, we mean within 10 parsecs or 30-odd light-years; that’s about 200 trillion miles or 2 million times the distance from the Sun to Earth; supernovae are that powerful and dangerous! There’s “solid evidence” that a couple of supernovae occurred around 2.5 and 6 million years ago, though safely far away at more than 100 parsecs. They appear to have strewn Earth with tiny amounts of the rare radioactive form of iron, iron-60 that forms only in supernovae. Finding this signature iron was an amazing feat of chemical detection by Anton Wallner and 13 colleagues in Germany and Australia. They recovered about 1,000 atoms of iron-60, among samples of ocean sediments containing some sextillions of other atoms!
Next question – can closer supernovae occur? After all, there are about 100 billion stars in the Milky Way. Supernovae to the rescue, themselves. The local ones blew away nearby stars, beyond the “kill radius” for us.
This has been an outreach activity of the Las Cruces Academy, viewable at GreatSchools.org
