According to the researchers, our own star could also behave in an equally violent way, with serious consequences for Earth.
An international team of astronomers, led by Kosuke Nomekata of the National Astronomical Observatory of Japan, has just witnessed the largest coronal mass ejection ever recorded, tens of times more intense than what scientists can see in our solar system. The responsible star, EK Draconis, violently expelled an unprecedented amount of energy and charged particles. If the Sun ever did something similar, the Earth’s magnetosphere, the natural ‘shield’ that protects us from similar events, would not be able to prevent the lethal radiation from reaching the Earth’s surface. The disturbing finding has just been published in ‘Nature Astronomy’.
According to Yuta Notsu, from the University of Colorado at Boulder and co-author of the study, the researchers were studying how solar storms occur in other stars similar to our own.
The Sun ‘fires’ this type of ejection on a regular basis. They are made up of clouds of extremely hot particles, or plasma, that can hurtle through space at speeds of millions of miles per hour. And if a coronal mass ejection hits Earth squarely, it could fry orbiting satellites and burn out transformers in power grids that serve our cities. on Earth and human society.
During their investigation, Namekata, Notsu, and their colleagues used ground-based and space-based telescopes to observe EK Draconis, 111 light-years away, which looks like a young version of the sun. In April 2020, the team watched as this star ejected a scorching cloud of plasma with a mass of 1 billion trillion kilograms, more than 10 times larger than the most powerful coronal mass ejection ever recorded from a Sun-like star.
It can happen in the Sun
According to Notsu, “This type of large-mass ejection could theoretically also occur on our Sun. ‘This observation may help us better understand how similar events may have affected Earth and even Mars over billions of years.’ years”. The researcher explains that coronal mass ejections often occur just after the star emits a strong flash, a sudden and very bright burst of radiation that can spread out into space.
On the Sun, this sequence of events is usually quite ‘quiet’, at least since scientists regularly study solar behavior. But in 2019 Notsu and his colleagues published a paper showing that young Sun-like stars are capable of producing flares like our own, but tens, or even hundreds of times more powerful. And in theory, such a ‘superflare’ could also occur in Earth’s Sun, though not very often, perhaps once every several thousand years.
Still, the Namekata and Notsu team undertook their study to answer one question: could a superflare also lead to a super coronal mass ejection? “Superflares are much larger than the flares we see emerging from the Sun. So we suspect they would also produce much larger mass ejections. Until recently, that was just conjecture.”
To find out the truth, the researchers decided to study EK Drakonis, a star that is the same size as the Sun but is much younger, only about 100 million years old. In Notsu’s words, “it’s what our Sun looked like about 4.5 billion years ago.”
During the winter and spring of 2020, scientists observed the star for 32 nights. To do this, they used NASA’s TESS satellite, an instrument designed to discover transiting exoplanets, and the SEIMEI telescope, from Kyoto University. And on April 5, 2020, the bell rang: researchers watched as EK Draconis erupted into a superflare, a really big one. About 30 minutes later, the team observed what appeared to be a coronal mass ejection moving away from the star’s surface, a ‘monster’ moving at more than a million and a half km/h.
Which might not bode well for life on Earth, as the study hints that our Sun could also reach these extremes of violence. And while these kinds of superflares were certainly much more common during our star’s youth, there’s no indication that they can’t happen again from time to time. According to the study, this gigantic ejecta from the past could have helped make planets like Mars or Earth itself as we see them today.
The atmosphere of Mars today, Notsu concludes, is very thin compared to Earth’s. In the past, we thought that Mars had a much thicker atmosphere. Coronal mass ejections can help us understand what happened to the planet billions of years ago.”
