Young sun-like star may hold warnings for life on Earth


Astronomers spying on a star system tens of light years from Earth have, for the first time, observed a disturbing pyrotechnic spectacle: a star, named EK Draconis, ejected a huge explosion of energy and charged particles much more powerful than anything scientists have seen in our own solar system.

The researchers, including astrophysicist Yuta Notsu of the University of Colorado Boulder, will publish their results on December 9 in the journal Nature astronomy.

The study explores a stellar phenomenon called “coronal mass ejection,” sometimes referred to as a solar storm. Notsu explained that the sun regularly launches these kinds of eruptions – they are made up of clouds of extremely hot particles, or plasma, that can travel through space at speeds of millions of kilometers per hour. And that’s potentially bad news: If a coronal mass ejection hits Earth head-on, it could roast orbiting satellites and shut down power grids serving entire cities.

“Coronal mass ejections can have a serious impact on Earth and human society,” said Notsu, associate researcher at the Atmospheric and Space Physics Laboratory (LASP) at CU Boulder and the United States National Solar Observatory.

The new study, led by Kosuke Namekata of the National Astronomical Observatory of Japan and former visiting scholar at CU Boulder, also suggests they may get worse.

In this research, Namekata, Nostu, and their colleagues used telescopes on the ground and in space to observe EK Draconis, who looks like a young version of the sun. In April 2020, the team observed EK Draconis eject a burning plasma cloud with a mass of several billion kilograms, more than 10 times the size of the most powerful coronal mass ejection ever recorded from a star similar to the sun.

The event can serve as a warning about the dangerous weather conditions in space.

“This type of massive mass ejection could, theoretically, also occur on our sun,” Notsu said. “This observation may help us better understand how similar events may have affected Earth and even Mars for billions of years.”

Superflares erupt

Notsu explained that coronal mass ejections often occur right after a star has triggered a sudden, bright flare or explosion of radiation that can spread far into space.

Recent research, however, has suggested that on the sun, this sequence of events can be relatively calm, at least as far as scientists have observed it. In 2019, for example, Notsu and his colleagues published a study this showed that young sun-like stars around the galaxy appear to experience frequent super-eruptions, like our own solar flares, but dozens if not hundreds of times as powerful.

Such a super eruption could, theoretically, also occur on Earth’s sun, but not very often, perhaps once every several thousand years. Still, it made the Notsu team curious: Could a super eruption also lead to an equally super coronal mass ejection?

“Superflares are much bigger than the flares we see from the sun,” Notsu said. “So we think they would produce much larger mass ejections as well. But until recently, that was just a guess.

Danger from above

To find out, the researchers set their sights on EK Draconis. The curious star, Notsu explained, is roughly the same size as our sun, but, at only 100 million years old, it is relatively young in the cosmic sense.

“This is what our sun looked like 4.5 billion years ago,” Notsu said.

Researchers observed the star for 32 nights in winter and spring 2020 using NASA Satellite for the study of exoplanets in transit (TESS) and Kyoto University SEIMEI telescope. On April 5, Notsu and his colleagues were lucky: Researchers watched EK Draconis erupt into a super eruption, a very big one. About 30 minutes later, the team observed what appeared to be a coronal mass ejection moving away from the star’s surface. The researchers were only able to capture the first stage in the life of this ejection, called the “filament eruption” phase. But even so, it was a monster, moving at a maximum speed of about 1 million miles per hour.

It may not bode well for life on Earth, too: the team’s findings suggest that the sun may be capable of such violent extremes as well. But don’t hold your breath, like super eruptions, super coronal mass ejections are probably rare around our age sun.

Still, Notsu noted that huge mass ejections may have been much more common in the early years of the solar system. In other words, gigantic coronal mass ejections could have helped shape planets like Earth and Mars to what they look like today.

“The current atmosphere of Mars is very thin compared to that of Earth,” Notsu said. “In the past, we think Mars had a much thicker atmosphere. Coronal mass ejections can help us understand what happened to the planet for billions of years.

Co-authors of the new study include researchers from the National Astronomical Observatory of Japan, Hyogo University, Kyoto University, Kobe University, Tokyo Institute of Technology, from the University of Tokyo and Doshisha University.