Sunlike stars produce superflares once per century

Berlin, Germany (SPX) Dec 13, 2024 - The Sun, known for its volatile nature, has exhibited unusually intense solar storms this year, creating auroras visible even at lower latitudes. However, new research suggests that the Sun and its stellar relatives are capable of even more powerful events called superflares, which release over one octillion joules of energy in brief bursts. These findings come from a study analyzing data from NASA's Kepler space telescope, revealing the frequency of these rare but potent solar events.

"We cannot observe the Sun over thousands of years," explained Prof. Dr. Sami Solanki, Director at the Max Planck Institute for Solar System Research (MPS) and coauthor of the study. "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."

Tracking Superflare Activity Across Thousands of Stars

The study analyzed brightness fluctuations in 56,450 sunlike stars using data captured by the Kepler space telescope between 2009 and 2013. The dataset equates to approximately 220,000 years of stellar activity. Researchers identified 2,889 superflares on 2,527 stars, determining that sunlike stars, on average, experience a superflare roughly once every century.

To ensure accuracy, the team carefully selected stars similar to the Sun in surface temperature and brightness. They excluded potential errors such as cosmic interference, nearby passing objects, or unrelated stars in the Kepler images. "High performance dynamo computations of these solar-type stars easily explain the magnetic origins of the intense release of energy during such superflares," noted Dr. Allan Sacha Brun from the Commissariat of Atomic and Alternative Energies of Paris-Saclay and the University of Paris-Cite.

Surprising Frequency and Implications for the Sun

The study's findings challenge previous research, which suggested superflares occur far less frequently, with intervals ranging from 1,000 to 10,000 years. Earlier limitations stemmed from the inability to pinpoint exact sources of observed flares in dense stellar environments. The current study's methodology, however, provides a clearer, more reliable picture of superflare activity.

Historical evidence from Earth points to extreme solar particle events roughly every 1,500 years, as inferred from elevated levels of radioactive isotopes such as carbon-14 in tree rings and ice cores. These findings, however, may underestimate the Sun's superflare potential. "It is unclear whether gigantic flares are always accompanied by coronal mass ejections and what is the relationship between superflares and extreme solar particle events. This requires further investigation," commented coauthor Prof. Dr. Ilya Usoskin from the University of Oulu in Finland.

Preparing for Potential Hazards

The research underscores the need for vigilance. The Carrington Event of 1859, one of the most severe solar storms in recent history, caused widespread telegraph outages and other disruptions despite being significantly less energetic than a superflare. In today's world, such an event could jeopardize satellites and critical infrastructure.

Timely forecasting is essential for mitigating the impact of extreme space weather. From 2031, ESA's Vigil space probe will provide early warnings by observing the Sun from a unique vantage point, detecting dangerous solar activity before it impacts Earth. The MPS is currently developing a key instrument for this mission, the Polarimetric and Magnetic Imager.

"These results are a stark reminder that even the most extreme solar events are part of the Sun's natural repertoire," said Dr. Natalie Krivova from the MPS.

Research Report:Sun-like stars produce superflares roughly once per century