The collision of a cold interstellar cloud with the heliosphere, the protective shield of the solar system, caused it to shrink to the point that our planet was exposed to cosmic radiation for 10,000 years.
A group of researchers from various US scientific institutions has found evidence suggesting that the our system it may have collided with a dense interstellar cloud about two million years ago as it passed through the Milky Way, which may have altered both climate and evolution on Earth, the lBoston University reported this week. The solar system is surrounded by a protective plasma shield, the heliosphere, formed by a constant flow of charged particles, called the “solar wind”, coming from the Sun’s outermost atmosphere. Inside the heliosphere, the planets are protected by gamma rays, radiation coming from our galaxy and according to Space.com, some scientists think that this shielding was fundamental to the birth and evolution of life on our planet.
An encounter between the Sun and “something outside the solar system”
In new research published in the journal Nature Astronomy, evidence has been reported suggesting that one of the clouds cold ones of the Local Ribbon system, located in the constellation Lynx, may have collided with the heliosphere, interfering with the solar wind. This caused this protective shield to shrink to the point that both Earth and other planets were exposed to cosmic radiation for 10,000 years. The researchers reached this conclusion after mapping the location of the cold cloud in the interstellar medium, the vast space between star systems, as well as the trajectory our star took through the Milky Way two million years ago. “This paper is the first to quantitatively show that there was an encounter between the Sun and something outside the solar system which would have influenced the Earth’s climate“said scientist Merav Opher.
An increase in radioactive isotopes
According to Opher, it is possible that the meeting between the heliosphere and the cold cloud, composed mainly of hydrogen, coincides with increases in the radioactive isotopes plutonium-244 and iron-60 in Antarctic ice, deep ocean cores, and sample moles. Likewise, these elements contained in interstellar clouds, which originated in distant supernovae, were probably deposited on our planet while it was out ofheliosphere. “The indication of an increase in these elements about 2 or 3 million years ago provides us with compelling evidence that, in fact, the Sun passed through that cloud about 2 million years ago.”said Opher, who emphasized that the Earth and its climate have suffered “substantial impact” resulting from “exposure to cold medium interstellar clouds“, as well as by the increase in hydrogen in the atmosphere and radiation.
