Imagine the following scene. During any night, one of the numerous stars that titrate in the sky, a dying red giant and only a few light years away, begins to shine with a blinding intensity. It is not a fleeting flash, … but of a glow that increases to every second and that floods the night sky with a supernatural light.
The star has become a Supernova, a colossal cosmic explosion that releases, in an instant, more energy than the sun produces in its entire life. The night sky turns on, with the supernova turned into a glowing object that even exceeds the brightness of the full moon and that turns the nights in the day.
But that is just the beginning. As the explosion expands, a wave of high energy radiation, including gamma and x -ray rays, rushes towards our planet. At first, the Earth’s atmosphere acts as a shield, absorbing much of that radiation. But the intensity of the bombing is such that the barrier falls soon.
The radiation then penetrates the upper atmosphere and the ioniza, alters the chemistry of the ozone and weakens the protective layer that protects us from the lethal ultraviolet rays of the Sun. The northern and southern lights, usually confined to the polar regions, extend throughout the world, illuminating the skies with their hypnotic light curtains.
Ultraviolet radiation, already without obstacles, reaches the earth’s surface, wreaking havoc in life. The plants wither, the animals suffer burns and mutations, and skin cancer becomes an epidemic. The oceans, although they offer some more protection, are also affected, and marine life does not escape the catastrophe.
Days or weeks later a cosmic ray pulse, subatomic particles loaded with energy, also reaches the earth. Cosmic rays interact with the atmosphere and generate secondary particles waterfalls that reach the surface. They have the ability to alter DNA and produce mutations in living beings, with unpredictable consequences for the numerous creatures that populate the planet.
Over time, the Supernova fades, leaving behind a brilliant remnant of expanding gas and dust. It is no longer a threat, but continues to emit radiation and particles for thousands of years.
It seems a science fiction story, but a team of researchers led by astrophysicist Alexis Quintana, before at the British University of Keele and now in Alicante’s, believes that something similar could have already happened in our world. And at least twice. The work has just been published in ‘Monthly notices of the Royal Astronomical Society’.
Two mass extinctions
According to the study, two supernovae who exploded near our planet 372 and 445 million years could be to blame for the extinctions of the devonic and the ordovicical, respectively. Ordovician extinction killed 60 percent of marine invertebrates at a time when life was largely limited to the sea, while devonic, even more devastating, annihilated about 70 percent of all the species that existed at that time and led to great changes in the ecosystems of our old seas and lakes.
Until now, no previous investigation has managed to determine the causes caused by these two events, although it is believed that the two are related to the exhaustion of the Earth’s ozone layer, which has led to think that both could be related to supernova explosions.
In his article, Quintana and his colleagues support that possibility, and explain that the Supernovas Rate near our planet is consistent with both mass extinctions. “It is a great and illustrative example – written the authors – how mass stars can act as much as creators and destroyers of life.” During the explosions of Supernovas, in effect, and apart from the destruction they can cause around them, the heavy elements that help the development of life in the universe are created and spread through space.
«The explosions of Supernova – explains Quintana – provide heavy chemical elements to the interstellar environment, which are then used to form new stars and planets. But if a planet, including the Earth, is too close to this type of event, can suffer devastating effects ».
Nick Wright, from the University of Keele and co -author of the article, adds that «Supernova’s explosions are among the most energetic in the universe. If a massive star exploded like a Supernova near Earth, the results would be devastating for life. And our research suggests that this may have happened ».
Massive stars census
The researchers reached their conclusion after carrying out a ‘census’ of mass stars within a kiloparsec (around 3,260 light years) away from the sun. During their analysis, they studied both the distribution of the stars, known as OB stars, which are usually formed in little organized groups, such as the speed at which they arise in our galaxy.
The census allowed researchers to calculate the rate at which supernova are produced within the Milky Way, an example from which you can learn how these explosive events influence, the rest of the universe, in the production of supernova remains and stellar remnants such as black holes and neutron stars.
The data coincides
As part of his investigation, Quintana and his team also calculated the Supernovas rate within the 20 Parsecs del Sol, (about 65 light years) and then compared it to the approximate rate of mass extinction events in the earth that had previously been attributed to nearby supernovae, which excludes extinctions linked to other factors, such as asteroid impacts or volcanic eruptions.
When comparing the two data sets, the researchers realized that their work supports the theory that two Supernovas could have been responsible for the extinctions of the devonic and the ordovicical, two of the five greatest massive extinctions known in the history of our planet.
“We calculate the Supernovas Rate near the Earth,” explains Wright, “and we find that it is consistent with the rate of mass extinction events on our planet linked to external forces, such as Supernovas.”
According to the study, in galaxies such as our Milky Way, approximately one or two supernovas occur every century, or even more spacedly, but the good news is that there are only two nearby stars that could explode as supernovae in the coming millions of years: Antares and Betheteuse. And both are more than 500 light years from us, a distance that the simulations made so far consider as safe.
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