Star explosions: an unsuspected impact for our climate?
The remanent of Supernova Cassiopée saw in multilongours of waves. © NASA / ESA
Has a researcher showed one of the causes of climate change on earth? Supernovæ, these cataclysmic explosions of stars, took place more or less far from the blue planet during its existence, and many scientists believe that they have played a real role in the evolution of our world and its climate. The question here is how very energetic particles, especially X -rays, influenced the composition of our atmosphere. A recent study published in the Monthly Notices of the Royal Astronomical Society set out to understand this by looking for traces of these impacts during the most recent era, known as the Quaternary, started 2.5 million years ago. And his conclusions are amazing.
G. Robert Brakenridge of the University of Arizona, author of the study, notes that eight supernovæ “recent” (on an astronomical scale is understood) and sufficiently close, that is to say within 1800 light years approximately, are interesting candidates since their flow of particles could reach the earth.
When the trees tell the impact of the supernovæ
The crab supernova results from an explosion of massive star observed 1000 years ago, the remanery of which continues to evolve. © Hartmann
This researcher studied the rings of trees covering a period of 15,000 years, a time required, because the flow of particles emitted by a supernova does not necessarily travel at the speed of light, being often slowed down by the environment it crosses. This is how G. Robert Brakenridge identified 15 radioactive carbon peaks which he thinks of being able to associate with supernovæ.
He therefore created a new model of interactions between supernova emission flows and the earth’s atmosphere. For example, in the case of an influx of high energy photons, they would weaken the ozone layer that protects the earth and its inhabitants from ultraviolet. This radiation would also degrade methane from the atmosphere, so would reduce the greenhouse effect. The consequences could be an extinction of certain species, fires and a decrease in temperatures.
“When nearby supernovae occurs in the future, radiation could have a fairly dramatic effect on human societyexplains the researcher at the University of Arizona. We need to know if they have actually caused environmental changes in the past. ”
This work does not alone solve the mystery complex of interactions between the supernovæ and the atmosphere of the earth, but it contributes to its measure.
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