When we think about mass extinctions, we almost always The asteroid that wiped out the dinosaurs comes to mind. But the universe has much more spectacular ways of reconfiguring life, as pointed out a scientific study which suggests that at least two of the ‘Big Five‘Earth extinctions were not caused by space rocks, but by the lethal radiation of stars exploding very close to our solar system.
The study. The research, led by Alexis L. Quintana of the University of Alicante, has complicated the most complete census to date of OB type starsthe “heavyweights” of the galaxy. These stars are incredibly large, hot and luminous, and they live fast and die young, ending their lives in titanic explosions known as core collapse supernovae (ccSN).
Space bombs. The team in this case has mapped 24,706 of these stars within a radius of 1 kiloparsec (about 3,260 light years) around the Sun. And with this map, they have been able to calculate something crucial: the frequency with which one of these cosmic bombs explodes in our neighborhood.
The key fact is chilling: they estimate that a supernova close enough (about 20 parsecs or 65 light years) to wreak havoc on Earth that occurs about 2.5 times every billion years. This figure, which may seem low, fits eerily into the fossil record.
A death mechanism. How exactly would a nearby supernova kill you? It’s not the blast wave, but the radiation. Such an energetic and upcoming explosion would bathe our planet in a torrent of gamma and cosmic rays, tearing apart our ozone layer. Without that protective shield, ultraviolet radiation from our own Sun became lethal, sterilizing the planet’s surface and causing ecological collapse.
Specifically, the study points out that this rate of 2.5 events per billion years is “consistent” with the fact that one or more of the mass extinctions recorded on Earth were caused by this mechanism. Specifically, they point to two devastating events:
Both extinctions have been linked by other studies to periods of intense glaciation and, crucially, a drastic reduction in atmospheric ozone, a “murder weapon” that points directly to a cosmic culprit.
Updates. Beyond the threat to Earth, the new OB star census has allowed the team to recalculate the overall supernova rate for the entire planet. Milky Way. And here there has been a surprise: it is lower than we thought.
Previous calculations put the rate at 1 or 2 explosions per century. The new study lowers it to 0.4 – 0.5 supernovae per century. The authors attribute this difference to the fact that their census is more precise and reliable thanks to Gaia data, since the models of how stars evolve have improved.
This new figure is not just an astronomical curiosity; It is fundamental data for other fields of physics. For example, it is vital for calculating the frequency with which we should be able to detect gravitational waves coming from these explosions within our own galaxy.
Our protection. Fortunately, a look at our current stellar neighborhood is reassuring. Although there are massive stars that we know will explode “soon” (in astronomical time), such as the famous red supergiants Antares and Betelgeuse, both are hundreds of light years away.
They are too far away to fry us with their radiation, but close enough that when they finally detonate (which could happen tomorrow or 100,000 years from now), they will give us a light show in the sky that will last for weeks. Meanwhile, we now have a new suspect to blame for some of the worst catastrophes in the history of life, long before humans came along to witness it.
Images | Aron Visuals 愚木混株 Yumu
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