Superflares occur on sun-like stars roughly once per century

Sun-like stars experience superflares approximately once every 100 years, according to new research from the Max Planck Institute for Solar System Research and collaborating institutions.

Analysis was conducted using Kepler Space Telescope data which covered 56 450 Sun-like stars and identified 2 889 superflares on 2 527 stars, suggesting that our own Sun might be capable of such extreme events.

“We were very surprised that Sun-like stars are prone to such frequent superflares,” Valeriy Vasilyev from Max Planck Institute and the lead author stated.

Superflares are immense bursts of electromagnetic radiation similar to solar flares but with more energy, reaching up to 10³⁶ ergs. They can be thousands of times more powerful than the most intense solar flares ever recorded. The events can impact planetary atmospheres and magnetospheres and can pose potential risks to modern technology and space operations.

Researchers examined Kepler mission photometry data from 2009 to 2013. The sample included main-sequence stars with effective temperatures between 5 000 K and 6 500 K and absolute magnitudes between 4 and 6 mag. A flare detection algorithm identified events where light curve fluctuations exceeded five standard deviations (5σ).

The findings reveal the detection of 2 889 superflares on 2 527 Sun-like stars with flare energies ranging from 10³³ to 10³⁶ ergs. The occurrence of superflares with energies equal to or greater than 10³⁴ ergs happens approximately once per century. The frequency of these flares follows a power-law distribution.

Possible effects on earth

The Carrington Event of 1859 was one of the most powerful solar storms recorded. It had an estimated energy of 4 × 10³² to 6 × 10³² ergs and caused widespread telegraph failures and intense auroras. However, research indicates that superflares could be 100 times stronger.

“We cannot observe the Sun over thousands of years. Instead, however, we can monitor the behavior of thousands of stars very similar to the Sun over short periods of time. This helps us to estimate how frequently superflares occur,” Sami K. Solanki, a solar physicist commented.

If a superflare were to occur today, satellites, power grids, and communication systems could face severe disruptions. High-energy radiation from such an event could also disturb Earth’s upper atmosphere leading to prolonged radio blackouts.

Superflare frequency on sun-like stars

Researchers found that superflares ≥ 10³⁴ ergs occur with a frequency of (8.63 ± 0.20) × 10^-3 per year per star, or approximately once per century by applying a power-law model to the data. Previous studies estimated a much lower frequency which ranged from once per 1 000 to 10 000 years.

The research categorized stars according to their temperature range between 5 500 and 6 000 K. The classification also considered photometric variability with an Rvar of less than 0.3% and rotation periods ranging from 20 to 30 days.

Superflare occurrence rates remained largely unchanged regardless of the criteria.

Could our star generate a superflare?

The study indicates that Sun-like stars exhibit similar flare patterns to the Sun, suggesting that our star could experience a superflare. The most powerful solar flare in modern times, recorded on October 28, 2003, had an estimated energy of 7 × 10³² ergs. It implies the Sun has the potential for stronger eruptions while below the superflare threshold.

“The new data are a stark reminder that even the most extreme solar events are part of the Sun’s natural repertoire,” Natalie Krivova, co-author of the study stated.

Tracing solar activity through cosmogenic isotopes

Direct solar flare observations have been available for fewer than 200 years. Researchers use cosmogenic isotopes such as carbon-14 (¹⁴C) in tree rings and beryllium-10 (¹⁰Be) in ice cores to track past solar activity.

Studies indicate 5 confirmed extreme solar energetic particle (SEP) events over the last 10 000 years which suggests an occurrence rate of 10^-3 per year. The exact relationship between SEP events and superflares remains unclear.

Predicting future superflares

The timing of the next solar superflare remains uncertain. Some Sun-like stars exhibit superflares while others do not which suggests that factors such as starspots and magnetic complexity influence their occurrence.

The study accounted for this by excluding unresolved binaries while 30% of flaring stars in the Kepler data were binary systems.

Monitoring the sun for extreme events

Space agencies are enhancing solar observation missions and space weather prediction models given the potential risks.

The European Space Agency (ESA) plans to launch the Vigil space probe in 2031 which will provide real-time solar monitoring from a unique vantage point.

The research reinforces the need for continued solar observation and preparedness for space weather events. Historical data and stellar observations indicate that superflares are part of natural stellar activity while the Sun has remained relatively stable.

References:

¹ Sun-like stars produce superflares roughly once per century, Valeriy Vasilyev, Timo Reinhold, Alexander I. Shapiro, et. al., Cornell University – December 16, 2024 – https://doi.org/10.48550/arXiv.2412.12265 – OPEN ACCESS

Rishika Yadav

Rishika holds a Master’s in International Studies from Stella Maris College, Chennai, India, where she earned a gold medal, and an MCA from the University of Mysore, Karnataka, India. Previously, she served as a Research Assistant at the National Institute of Advanced Studies, Indian Institute of Science, Bengaluru, India. During her tenure, she contributed as a Junior Writer for Europe Monitor on the Global Politics website and as an Assistant Editor for The World This Week. Her work has also been published in The Hindu newspaper, showing her expertise in global affairs. Rishika is also a recipient of the Women Empowerment Award at the district level in Haryana, India, in 2022.

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