In the search for “potentially habitable” extrasolar planets, one of the main things scientists look at is stellar activity.
While stars like ours, a yellow G-type (G2V) dwarf, are considered stable over time, other classes are variable and prone to spurts – particularly red M-type dwarf stars.
Even if a star has multiple planets orbiting its habitable zone (HZ), the tendency to periodically ignite could make those planets completely uninhabitable.
According to a new study, stars like ours may not be as stable as previously thought. By observing EK Draconis, a yellow G1.5V dwarf located 110.71 light years away [within the borders of the Draco constellation, meaning Dragon], an international team of astronomers witnessed a massive coronal mass ejection that eclipsed anything we have ever seen in our solar system.
These observations suggest that these ejections can worsen over time, which could be a terrible warning to life here on Earth.
The study, which appeared in the December 9 issue of the journal Nature astronomy, was led by Dr Kosuke Namekata, a researcher at Kyoto University, the National Astronomical Observatory of Japan (NAOJ) and the National solar observatory (ONS).
He was joined by researchers from CU Boulder’s Atmospheric and Space Physics Laboratory (LASP), the Nishi-Harima Astronomical Observatory (NHAO), the Tokyo Institute of Technology, the Graduate School of Advanced Integrated Studies in Human Survivability, and several universities.
Their study explores a stellar phenomenon known as “coronal mass ejection” (CME), aka. a solar storm. These ejections, which occur regularly with our Sun, often accompany a stellar eruption (or a sudden, bright explosion of radiation).
When they occur, CMEs send clouds of extremely hot charged particles (aka plasma) at extremely high speeds into space. While the Earth is protected from charged particles by its planetary magnetic field, a CME could cause significant damage if it collides with Earth head-on.
Astronauts in orbit would be exposed to deadly levels of radiation, satellites would be disabled, and earth infrastructure (such as power grids) would be destroyed.
Earth has experienced several powerful geomagnetic storms over time, the best-known example of which is the Carrington event in 1859. Several of these events have occurred in Earth’s history and are typically several thousand years apart. ‘years.
While studying EK Draconis, the research team observed evidence that super-flares can get worse for solar-type stars over time. As co-author Yuta Notsu (LASP) explained in a recent CU Boulder Today Press release:
“Coronal mass ejections can have a serious impact on Earth and human society. This type of large mass ejection could, theoretically, also occur on our sun. This observation may help us better understand how similar events occur. could have affected Earth and even Mars over billions of years. “
Research is based on Previous search by co-author Yuta Notsu, who was joined by many of the researchers who conducted this latest study. They showed how young Sun-like stars undergo frequent super-flares that are tens to hundreds of times more powerful than solar flares.
The Sun is known to experience super-eruptions, which seem to occur once every several thousand years. This begged the question: Could a super eruption also lead to an equally massive “super coronal mass ejection”?
While astronomers have speculated on a possible relationship between these two phenomena, no evidence has been found for this before.
To study this possibility, Namekata, Notsu and their colleagues decided to study EK Draconis, which is similar to our Sun in terms of size and mass but is significantly young in comparison (100 million years ago compared to our Sun, which is 4.6 billion years old). year).
For their observations, Namekata, Notsu and their colleagues used the Satellite for the study of exoplanets in transit (TESS) and Kyoto University SEIMEI telescope observe EK Draconis (who looks like a young version of the Sun) for 32 nights in winter and spring 2020.
On April 5, 2020, the team observed the eruption of EK Draconis in a super eruption, followed 30 minutes later by a massive ejection of super hot plasma. Said Notsu:
“This type of massive 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. what our Sun looked like 4.5 billion years ago. “
The team could only observe the first stage of the ejection life – the “filament eruption” phase – but were still able to obtain estimates of mass and velocity.
According to their study, the cloud was more than ten times larger than the strongest CME on record from a Sun-like star and had a top speed of around 1.6 million km (1 million mph ). The event could indicate how dangerous space weather can be.
If such an eruption were to occur from our Sun, it would have the potential to strip Earth’s atmosphere and render our planet largely barren.
While their findings indicate that the Sun might be capable of such violent extremes, they also suggest that super-eruptions and super CMEs are likely rare for stars as old as the Sun. But as Notsu explained, maybe super CMEs were much more common billions of years ago, when our solar system was still forming.
Super CMEs, in other words, could have played a role in the evolution of planets like Earth and Mars, which includes how one gave birth to life while the other did not. did not.
“The current atmosphere of Mars is very thin compared to that of Earth,” he said. “In the past, we believe Mars had a much thicker atmosphere. Coronal mass ejections can help us understand what happened to the planet for billions of years.”
This same knowledge could be useful if and when future generations begin to live on Mars. Protecting the atmosphere from solar activity (including CMEs) will allow the atmosphere to replenish itself over time, making the planet warmer, wetter, and overall more livable!