A star like the Sun can produce a superflare every century

Dec. 13 () –

An analysis of data from 56,450 Sun-like stars taken by the NASA Kepler space telescope between 2009 and 2013 reveals that our star can produce one superflare per century.

Modern space telescopes observe thousands upon thousands of stars and record their brightness fluctuations in visible light. Superflares, which release amounts of energy of more than one octillion joules in a short period of time, They show up in the observation data as short, sharp brightness spikes.

“We cannot observe the Sun for thousands of years,” explains Prof. Dr. Sami Solanki, director of the MPS (Max Planck Society) and co-author of the research, about the basic idea of ​​it. “However, we can observe the behavior of thousands of stars very similar to the Sun for short periods of time. This helps us estimate how often superflares occur.“he adds.

“Taken together, the Kepler data provide us with evidence for 220,000 years of stellar activity,” says another co-author of the study, Professor Dr. Alexander Shapiro of the University of Graz.

A decisive factor for the studio was the careful selection of stars to take into account. After all, the stars chosen had to be especially close “relatives” of the Sun. Therefore, scientists They only admitted stars whose surface temperature and brightness were similar to those of the Sun.

The researchers also ruled out numerous sources of error, such as cosmic radiation, passing asteroids or comets, as well as non-Sun-like stars that in Kepler images can, by chance, explode in the vicinity of a Sun-like star. To do this, the team carefully analyzed images of each possible superflare (just a few pixels in size) and only counted those events that could be reliably assigned to one of the selected stars.

In this way, the researchers identified 2,889 superflares in 2,527 of the 56,450 stars observed. This means that, on average, a Sun-like star produces a superflare about once a century.

“High-throughput calculations of these dynamo-solar-type stars easily explain the magnetic origins of the intense energy release during these superflares,” he said. in a statement co-author Dr. Allan Sacha Brun of the Paris-Saclay Commissariat for Atomic and Alternative Energies and the University of Paris-Cité.

“We were very surprised that stars similar to the Sun are prone to such frequent solar flares“said first author Dr. Valeriy Vasilyev of the MPS. Previous studies by other research groups had found average intervals of a thousand or even ten thousand years.

However, previous studies were unable to determine the exact source of the observed flare and therefore had to limit themselves to stars that did not have very close neighbors in the telescope images. The current study is the most precise and sensitive to date.

Studies looking for evidence of violent solar storms impacting Earth have also suggested longer average time intervals between extreme solar events. When a particularly high flow of energetic particles from the Sun reaches the Earth’s atmosphere, They produce a detectable amount of radioactive atoms such as the radioactive carbon isotope 14C.

These atoms are then deposited in natural archives such as tree rings and glacial ice. Even thousands of years later, the sudden influx of high-energy solar particles can be deduced by measuring the amount of 14C with modern technologies.

ONE EXTREME EVENT EVERY 1,500 YEARS

In this way, the researchers were able to identify five extreme solar particle events and three candidates in the last twelve thousand years of the Holocene, resulting in an average occurrence rate of once every 1,500 years.

The most violent is believed to have occurred in 775 AD.. However, it is quite possible that more such violent particle events and also more superflares occurred on the Sun in the past.

“It is not clear whether giant flares are always accompanied by coronal mass ejections and what the relationship is between superflares and extreme solar particle events. This requires further research,” said co-author Professor Dr. Ilya Usoskin of the University of Oulu in Finland. Therefore, Looking at ground-based evidence of past extreme solar events could underestimate the frequency of superflares.