Sonne: When is the Superflare coming?

Even our star can produce rare, but extremely violent bursts

Radiation outbreak on the sun. Our star can apparently produce far more violent eruptions than previously thought - so-called superflares. © NASA / Goddard Space Flight Center
Read out

Latent threat: Astronomers have found that even stars like the sun can produce so-called superflares. These enormous bursts of radiation are a thousand times stronger than the strongest solar storms and could almost paralyze our modern civilization. However, in the sun only every few thousand years can be expected with such an extreme outbreak, as the researchers report.

Our sun is 4.6 billion years old and therefore relatively quiet for a star. Although it often produces solar storms in which solar plasma is thrown into space and high-energy radiation in the form of flares is released. If such solar storms hit the earth, they can cause serious consequences such as the collapse of power grids and the breakdown of telecommunications.

One million times stronger than the strongest solar storm

But it is even more extreme: some young, fast-rotating stars produce bursts of rays, which can be up to a million times stronger than the strongest sunflare, as observations with space telescopes show. However, the sun's magnetic field is far too weak to produce such superflares - at least that's what they thought.

But already observations with the space telescope Kepler have aroused doubts. Because astronomers also detected superflares around older sun-like stars. However, it remained unclear whether these were not hidden double stars. "So we did not know if such enormous flares could possibly occur on the Sun, albeit at a very low frequency, " explains Yuta Notsu from Kyoto University.

Even older stars produce superflares

To clarify this, Nossu and his team have again targeted 43 Sun-like stars with a telescope in the US and the Gaia Space Telescope. In all, superflares had been observed before. The researchers are now specifically investigating how old these stars are, how often superflares occur in them and whether they really are single stars. display

The result: Superflares are in fact not an exclusive phenomenon of young stars. However, with an energy of around 100 billion petajoules, they produce particularly strong bursts of radiation, as the astronomers report. But even older, slowly rotating stars like the sun can produce superflares that are only an order of magnitude smaller, according to Notsu and his colleagues.

When was the last super-eruption of the sun?

After all, in the sun, such Superflares are rather rare. "In sun-like stars around the age of 4.6 billion years, superflares of this magnitude would occur once every 2, 000 to 3, 000 years, " the astronomers report. Radiation bursts of the hundred to thousand times the strength of conventional flares could be somewhat more common. Already, they would be enough to hit our modern civilization based on electronics and telecommunications.

The problem, however, is that we do not know how long the sun's last superflare lasts. This makes it difficult to estimate the current risk for such an event. In fact, there are indications that the earth has already been hit by fierce jet showers from space among other things, almost 7, 500 years ago and in the year 775 and 994. Notsu and his colleagues consider it It's likely that these were extreme sunflares.

Already in the next hundred years?

"This suggests that extreme solar flares have even occurred several times in the last 1, 000 years, " say the astronomers. The next superflare of the sun is therefore only a matter of time. "There is a good chance that we will see such an event in the next 100 years or so, " predicts Notsu. In contrast to our ancestors, who heard of little more than increased polar lights, the consequences for us should be more severe. (The Astrophysical Journal, 2019; doi: 10.3847 / 1538-4357 / ab14e6)

Source: University of Colorado at Boulder

- Nadja Podbregar