Mega Explosion From Sun Captured in Tree Ring From Almost 10,000 Years Ago

Scientists have found evidence of solar explosions thousands of years ago by the impact they had on tree rings—and estimate that potentially disruptive events could happen as often as once every 400 years.

Today, scientists know that the sun does not always behave the same way. It goes through periods of enhanced activity and sometimes produces eruptions such as solar flares or coronal mass ejections, which may cause brief but powerful bursts of solar radiation to hit Earth.

Such events often pass unnoticed for most of us, but they have the potential to seriously disrupt electronics or damage power systems if they're powerful enough.

Scientists are therefore keen to study ancient solar activity so that they can gain critical information on previous extreme solar events.

One way they can do this is by studying tree rings. Tree rings are circular shapes embedded all the way through tree trunks as a result of the tree expanding over time. By looking at tree rings, scientists can work out how old the tree is and what the weather was like during earlier periods of the tree's life.

Trees are sensitive to local climate conditions, so a particularly old tree can give useful insights into what a particular part of the world was like potentially thousands of years ago.

By studying tree rings in Switzerland, Germany, Ireland, Russia, and the U.S., a team of researchers has been able to gain insight into solar activity more than 9,000 years ago by studying a type of cosmogenic radionuclide called carbon-14 which is present in tree rings.

Cosmogenic radionuclides, also called cosmogenic isotopes, are atoms produced when radiation from space collides with an atom here on Earth.

During periods of increased solar activity, there may be a short-term increase in the production of carbon-14, which is then stored in tree rings or polar ice.

In a report published on Monday in the journal Nature Communications, scientists describe a two percent increase in atmospheric carbon-14 levels stored in multiple tree rings that occurred in 7176 and 5259 BCE, which exceed the strongest previously known carbon-14 event if the Earth's geomagnetic field is not taken into account.

"Ranking among the three largest short-term carbon-14 production events, the impact of the newly discovered events would have been catastrophic for aircraft, satellites, modern telecommunication and computer systems if they occurred today," the report states.

Existing data suggests that strong solar energy burst events hit Earth perhaps once every 400 to 2,400 years on average. More data will allow for a more precise measurement.

Solar flare
An image of a solar flare seen on the lower right-hand side of the sun, pictured by NASA's Solar Dynamics Observatory in October, 2014. Solar flares and other types of solar activity can disrupt electrical systems on Earth. NASA/SDO