Earlier this year, the Earth experienced two geomagnetic storms caused by bursts of radiation from the Sun that affected satellites in space and communication systems on the ground. It turns out that the Sun may be capable of much more powerful solar flares.
The Sun is a giant, hot ball of plasma that holds our solar system together, but there are billions of stars like it in space. Although scientists have only been studying the Sun up close for the past 60 years, observing Sun-like stars at different stages of their lives can help predict the behavior of Earth’s host star. Hoping to find out whether the Sun is capable of producing superflares, which are thousands of times more powerful than solar flares, the team analyzed data from 56,000 Sun-like stars. The team detected 2,889 superflares on 2,527 stars, indicating that stars with similar temperatures and variability to our Sun generate superflares about once a century.
So far, scientists are not sure whether the Sun is capable of causing a superflare, as no such event has been recorded on our host star. Extreme solar activity in the past has left its mark on Earth in the form of isotope bursts, but these events do not reach the energy level expected from a superflare, according to the study. Nevertheless, the results of the study, published today in the journal Science, not only give scientists a better understanding of our star, but may also help them better predict future geomagnetic storms that interfere with our technology on Earth.
“We wanted to determine how often our Sun produces superflares, but the duration of direct solar observations is relatively short,” said Valery Vasiliev of the Max Planck Institute for Solar System Research, lead author of the new study.
Instead of relying on observations of the Sun, the researchers turned to data collected by NASA’s Kepler space telescope, which has been scouring the cosmos for exoplanets for nine years. “An alternative approach is to analyze the big data collected by space telescopes like Kepler… By observing approximately 56,000 Sun-like stars over the course of four years, we have actually accumulated data equivalent to about 220,000 years of observations of the Sun,” Vasiliev added.
The results also showed that the frequency of superflares coincides with previously observed patterns of solar flares on the Sun, indicating that there is a common underlying mechanism. An ordinary solar flare – a giant explosion on the Sun that ejects high-speed particles into space – emits energy equivalent to ten million times that of a volcanic eruption on Earth. Superflares, on the other hand, are 10,000 times more powerful than solar flares.
“Such storms can seriously disrupt the operation of technological systems.”
Solar flares are a natural phenomenon of solar activity. The Sun goes through an 11-year cycle that affects the level of its solar activity. This year, NASA confirmed that the Sun is in its solar maximum, a period of increased activity characterized by intense solar flares and coronal mass ejections. In May, a G5 geomagnetic storm, or extreme geomagnetic storm, hit the Earth as a result of large plasma emissions from the Sun’s corona (also known as a coronal mass ejection). The G5 storm, the first to hit the Earth in 20 years, caused some devastating effects on the Earth’s power grid and led to a change in the position of thousands of satellites in low Earth orbits.
“If it is accompanied by a coronal mass ejection (CME), [the superflare] could lead to extreme geomagnetic storms on Earth,” Vasiliev said. “Such storms can seriously disrupt the operation of technological systems.”
The researcher noted that further detailed studies are needed to determine whether the observed stars are different from the Sun, or whether their activity reflects the future potential of our host star. The Sun is considered a typical yellow dwarf star. However, according to Vasiliev, it was recently discovered that the Sun exhibits much less variability in brightness compared to other sun-like stars in the field of view of the Kepler telescope. “This indicates that the Sun is less active than most solar analogs,” Vasiliev added.
The study took this factor into account by including a larger and more representative sample of Sun-like stars, but it is not clear whether this will affect the Sun’s ability to produce superflares similar to its stellar counterparts.
