Artist's depiction of the star EK Draconis ejecting a coronal mass ejection as two planets orbit. (Credit:听National Astronomical Observatory of Japan)
Astronomers spying on a stellar system located dozens of lightyears from Earth have, for the first time, observed a troubling fireworks show: A star named EK Draconis ejected a massive burst of energy and charged particles in an event that was 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, Dec. 9 in the journal Nature Astronomy.
The study explores a stellar phenomenon called a 鈥渃oronal mass ejection,鈥� sometimes known as a solar storm. Notsu explained the sun shoots out these sorts of eruptions on a regular basis. They鈥檙e made up of clouds of extremely hot particles, or plasma that can hurtle through space at speeds of millions of miles per hour. And they鈥檙e potentially bad news: If a coronal mass ejection hit Earth dead-on, it could fry satellites in orbit and shut down the power grids serving entire cities.
鈥淐oronal mass ejections can have a serious impact on Earth and human society,鈥� said Notsu, a research associate at the (LASP) at CU Boulder and the U.S. National Science Foundation鈥檚 .
The new study, led by the National Astronomical Observatory of Japan鈥檚 Kosuke Namekata鈥攆ormerly a visiting scholar at CU Boulder鈥攁lso suggests the ejections can get a lot worse.
A coronal mass ejection seen erupting from the surface of Earth's sun in 2015. (Credit: NASA)
In the research, Namekata, Nostu and their colleagues used telescopes on the ground and in space to peer at EK Draconis, which looks like a young version of the sun. In April 2020, the team observed EK Draconis ejecting a cloud of scorching-hot plasma with a mass in the quadrillions of kilograms鈥攎ore than 10 times bigger than the most powerful coronal mass ejection ever recorded from a sun-like star.
The event may serve as a warning of just how dangerous the weather in space can be.
鈥淭his kind of big mass ejection could, theoretically, also occur on our sun,鈥� Notsu said. 鈥淭his observation may help us to better understand how similar events may have affected Earth and even Mars over billions of years.鈥�
Superflares erupt
Notsu explained coronal mass ejections often come right after a star lets loose a flare, or a sudden and bright burst of radiation that can extend far out into space.
Recent research, however, has suggested that on the sun, this sequence of events may be relatively sedate, at least so far as scientists have observed. . In 2019, for example, Notsu and his colleagues published a study that showed that young sun-like stars around the galaxy seem to experience frequent superflares鈥攍ike our own solar flares but tens or even hundreds of times more powerful.
Such a superflare could also happen on Earth鈥檚 sun but not very often, maybe once every several thousand years. Still, it got Notsu鈥檚 team curious: Could a superflare also lead to an equally super coronal mass ejection?
鈥淪uperflares are much bigger than the flares that we see from the sun,鈥� Notsu said. 鈥淪o we suspect that they would also produce much bigger mass ejections. But until recently, that was just conjecture.鈥�
Danger from above
To find out, the researchers set their sights on EK Draconis. The curious star, Notsu explained, is about the same size as our sun, but, at just 100 million years old, it鈥檚 a relative youngster in a cosmic sense.
鈥淚t鈥檚 what our sun looked like 4.5 billion years ago,鈥� Notsu said.
The researchers observed the star for 32 nights in winter and spring 2020 using NASA鈥檚 Transiting Exoplanet Survey Satellite (TESS) and Kyoto University鈥檚 SEIMEI Telescope. And on April 5, Notsu and his colleagues got lucky: The researchers looked on 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 flying away from the star鈥檚 surface. The researchers were able to catch only the first step in that ejection鈥檚 life, called the 鈥渇ilament eruption鈥� phase. But even so, it was a monster, moving at a top speed of roughly 1 million miles per hour.
It may also not bode well for life on Earth: The team鈥檚 findings hint that the sun could also be capable of such violent extremes. But don鈥檛 hold your breath鈥攍ike superflares, super coronal mass ejections are probably rare for our getting-on-in-years sun.
Still, Notsu noted that huge mass ejections may have been much more common in the early years of the solar system. Gigantic coronal mass ejections, in other words, could have helped to shape planets like Earth and Mars into what they look like today.
鈥淭he atmosphere of present-day Mars is very thin compared to Earth鈥檚,鈥� Notsu said. 鈥淚n the past, we think Mars had a much thicker atmosphere. Coronal mass ejections may help us to understand what happened to the planet over billions of years.鈥�
Co-authors on the new study include researchers from the National Astronomical Observatory of Japan, University of Hyogo, Kyoto University, Kobe University, Tokyo Institute of Technology, the University of Tokyo and Doshisha University.
