Moreover, the survival and survival of life on Earth seems to be the result of good fortune. According to a new study of the history of the Milky Way, the best time and place to reveal life here, or now, is only 6 billion years ago on the edge of the galaxy.
That special place in space and time would have provided a protective world of the best protection against gamma-ray explosions and supernovae that tasted a place with deadly radiation.
About 4 billion years ago, the central regions of the galaxy (which comprise the Solar System) became safer than the periphery – safe enough for life to emerge, if not less safe. in which was the margin.
“Our work shows that, up to 6 billion years ago, with the exception of the peripheral regions of the Milky Way, which had very few planets, due to the formation of high stars and low metallurgy, planets subject to many explosive events that could have gone extinct, “explained astronaut Riccardo Spinelli of the University of Insubria and the National Institute for Astrophysics (INAF) in Italy.
Cosmic explosions are no joke. Incredibly dramatic events such as gamma-ray explosions and supernovae send cosmic radiation flying through space; so intense is the result that it can be fatal to life.
The Earth was not watertight, either. Extinction through our history has been linked to supernovae, including the extinction of the late Pliocene 2.6 million years ago and the late Devonian extinction 359 million years ago . Gamma-ray explosions, which are far rarer but much more powerful than supernovae, would be devastating as well.
Both events are linked to the life cycles of stars. Supernovae occur when a large star reaches the end of its main series life, or when a white dwarf assemblage material becomes unstable, ruling and kicking into a runaway fusion. Both situations lead to a massive explosion of stellar material into space.
Gamma-ray explosions are thought to be sputtered from stars falling into neutron stars or black holes, and we know that they can occur when neutron stars come together. We never saw one on the Milky way; the ones we find come from other galaxies millions of light years away – the most dynamic electromagnetic events in the Universe.
Scientists believe that a gamma-ray explosion 450 million years ago could have gone extinct in Ordovician destruction, before the age of the dinosaurs.
“Supernovae are more common in star-forming regions, where large stars are formed,” said astronaut Giancarlo Ghirlanda of the INAF.
“On the other hand, gamma-ray explosions prefer star-forming regions that are still badly trapped by heavy elements. In those regions, large stars formed by poor metal gas will ‘less loss of life during their lives due to stellar winds.So these stars are able to keep themselves in rapid rotation, a necessary condition for being able to launch, once that a black hole is created, a powerful jet. “
To find out which are the safest places to live, the research team carefully modeled the evolutionary history of the Milky Way, noting the regions most likely to harbor explosive activity. supernova no gamma-ray.
Their model hypothesized that the inner regions of the galaxy would have formed faster than the periphery; thus, the inner Milky Way would have been much more active in the creation of stars and cosmic explosions. Over time, the rate of star formation in the inner region decreased, but increased in the outer regions of the galaxy.
When the Universe was young, it was mostly filled with hydrogen and helium – the gases from which the first stars were made. Heavier elements were constructed from a dense mixture of nuclei; and even heavier elements from supernova explosions.
As the stars lived and died, the center of the Milky Way area became richer in heavier elements and metals.
As a result, this would have reduced gamma-ray explosions, making the central region – between about 6,500 and 26,000 light-years from the galactic center – safer than before.
“Excluding the very central regions, less than 6,500 light-years from the galactic center, where supernova eruptions are more frequent, our study suggests that there is an evolutionary pressure in each epoch. mostly certified by GRBs, “Spinelli said.
“Although they are much rarer events than supernovae, GRBs are able to disappear from greater distances: being the most dynamic events, they are the bazookas with the longest range.”
While the outskirts of Milky Ways were once safer than the central areas now, the news is getting better – for us, at least. According to the team’s study, in the last 500 million years the edge of Milky Way would appear to have been sterilized by two to five long gamma-ray explosions. On the other hand, the location of our Solar System was safer than ever.
But even the relative danger and reappearance of cosmic explosions could be fortunate for us.
“We note that the real-life life on planet Earth today shows that the destruction of many does not hinder the potential for the development of complex life,” the researchers wrote in their paper.
“On the other hand, it could be very much extinct at the right pace in the evolution of complex life forms on our home planet. “
So it may be necessary to take “safety” with a grain of salt.
The research was published in Astronomy & Astronomy.