A superflare from the sun could kill us all off, says an international team of scientists from Denmark, Italy and China. The scientists say they can now answer the question ‘Are superflares formed by the same mechanism as solar flares, and if so, can our Sun produce a superflare?’
They calculated that our Sun could be producing one superflare on its surface every thousand years.
Christoffer Karoff, who works at the Department of Geoscience, Aarhus University, Copenhagen in Denmark, and colleagues wrote about their latest study and findings in the prestigious journal Nature Communications (citation below).
In 2008, NASA’s Swift satellite picked up a record-setting flare from a star called EV Lacertae. This flare was thousands of times more powerful than the greatest observed solar flare. But because EV Lacertae is much farther from Earth than the sun, the flare did not appear as bright as a solar flare. It was the brightest flare ever observed from a star other than the Sun. (Image: nasa.gov).
Solar eruptions are common
Our planet is regularly struck by solar eruptions. These eruptions are the result of an accumulation of energetic particles that are flung away from the Sun into space. Some of them reach Earth, but do not harm us because our planet’s magnetic field (magnetosphere) protects us.
When these eruptions interact with our planet’s magnetic field they cause spectacular auroras. Most auroras are found far from the equator in the northern and southern hemispheres. In the north they are called Northern Lights (aurora borealis), and Southern Lights (aurora australis) in the south.
These beautiful auroras are a poetic reminder that our nearest star is an unpredictable neighbour.
An artist’s impression of our Sun (left) with a normal solar flare, and what it would look like with a superflare (right). (Image: University of Warwick)
When the Sun pours huge amounts of hot plasma during the large solar eruptions, there is the possibility of severe consequences on Earth.
Eruptions from our Sun, however, are nothing compared to the so called ‘superflares’ we observe on other stars.
Since they were discovered in large numbers by the Kepler mission four years ago, superflares have been a mystery.
Scientists wonder whether superflares and solar flares are formed in the same way. If that is the case, does it mean that our Sun could produce superflares?
Dr. Karoff and colleagues believe they now have the answer to this question.
The Sun – our dangerous neighbour
We know the Sun can produce gigantic eruptions that disrupt our radio communications as well as power supplies here on Earth.
The largest eruption observed by us occurred in September 1859, when colossal quantities of hot plasma from the Sun struck the Earth.
If a solar superflare hits Earth, the scene would be spectacular, even beautiful. However, could end up destroying us all.
While observing the Sun on 1st September 1859, astronomers saw how one of the dark spots on the surface suddenly lit up and shone brilliantly across the Sun.
Nobody had ever observed the phenomenon before, and therefore had no idea what was to come. On the morning of the following day, the first particles, from what we today know was a massive eruption on the Sun, reached our planet.
That 1859 solar storm is known as the Carrington Event. Auroras associated with the Carrington Event were visible as far south as Hawaii and Cuba, telegraph systems globally went berserk, and ice core records from Greenland suggest that the Earth’s protective ozone layer was damaged by the energetic particles from the solar storm.
Some star eruptions are incredibly large
In several other stars in our Universe, however, some eruptions up to 10,000 times larger than the Carrington Event have been observed.
Solar flares happen when large magnetic fields on the Sun’s surface collapse. When this occurs, enormous quantities of magnetic energy are released.
On Oct. 8, 2015, a photographer in Harstad, Norway captured this image of the dancing northern lights (Aurora borealis). (Image: nasa.gov)
Associate Professor Karoff and colleagues have used observations of magnetic fields on the surface of nearly 100,000 stars made with China’s new Guo Shou Jing telescope to show that these superflares are probably formed in the same way as our Sun’s solar flares.
Prof. Karoff said:
“The magnetic fields on the surface of stars with superflares are generally stronger than the magnetic fields on the surface of the Sun. This is exactly what we would expect, if superflares are formed in the same way as solar flares.”
Superflares from the Sun?
It would seem unlikely, therefore, that the Sun should be able to create a superflare, given that its magnetic field is too weak, wouldn’t it?
Out of all the stars with superflares that Prof. Karoff and colleagues analyzed, about 10% had a magnetic field with a strength either the same as or weaker than that of our Sun. Therefore, even though it is unlikely, it is definitely not impossible for the Sun to produce a superflare.
In an Abstract in the journal, the authors wrote:
“However, superflare stars with activity levels lower than, or comparable to, the Sun do exist, suggesting that solar flares and superflares most likely share the same origin.”
Prof. Karoff said:
“We certainly did not expect to find superflare stars with magnetic fields as week as the magnetic fields on the Sun. This opens the possibility that the Sun could generate a superflare – a very frightening thought.”
An eruption of this size striking the Earth today would have devastating consequences. Not only would all our electronic equipment be frazzled, our atmosphere would change significantly and our planet would lose the ability to support life, i.e. we would all die.
Has a superflare already hit Earth?
According to evidence from geological archives, our Sun may have produced a small superflare in AD 775. Tree rings show that abnormally large amounts of radioactive isotope 14C were formed in our planet’s atmosphere. 14C is formed when cosmic-ray particles from the Milky Way, or especially-energetic protons from the Sun, formed in connection with large solar eruptions, penetrate the Earth’s atmosphere.
According to studies using the Guo Shou Jing telescope, there was a small superflare in AD 775. This would have been a solar eruption between ten and one hundred times bigger than the largest solar eruption observed during the space age.
Prof. Karoff explained:
“One of the strengths of our study is that we can show how astronomical observations of superflares agree with Earth-based studies of radioactive isotopes in tree rings.”
In this way, by using observations from the Guo Shou Jing telescope, scientists can evaluate how often a star with a magnetic field similar to that of our Sun would experience a superflare.
According to this new study, the Sun should experience a relatively small superflare every millennium. This is in agreement with the notion that the event in AD 775 and another similar event in AD 993 were caused by small superflares on the Sun.
Citation: “Observational evidence for enhanced magnetic activity of superflare stars,” Christoffer Karoff, Mads Faurschou Knudsen, Peter De Cat, Alfio Bonanno, Alexandra Fogtmann-Schulz, Jianning Fu, Antonio Frasca, Fadil Inceoglu, Jesper Olsen, Yong Zhang, Yonghui Hou, Yuefei Wang, Jianrong Shi & Wei Zhang. Nature Communications. 24 March 2016. DOI: 10.1038/ncomms11058.
Video – The largest Solar Storm in History: The Carrington Event