The Sun has long been recognised to experience different periods of solar activity. Galileo first pointed a telescope at the sun in 1612, and astronomers have since observed and recorded the coming and going of sunspots.
Such long-term research has informed much about the Sun's activity, with increased sunspots broadly associated with increased activity occurring the core of our solar system’s sole star.
Only for the last 400 years and using the extremely laborious counting method
Dr Lukas Wacker
The most famous solar cycle of them all is the Schwabe cycle, with its 11-year cadence.Insurance Loans Mortgage Attorney Credit Lawyer
But there are other cycles of far longer duration which have a well-documented effect on Earth and its environment.
However, scientists’ attempts to understand more extended cycles have been frustrated, until they learned how the Sun has left some tantalising clues within tree rings.
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Solar mystery: Scientists have turned to tree rings in bid to understand Sun’s strange 11-year cycle (Image: Getty)
Solar mystery: A simple schematic of an accelerator mass spectrometer. (Image: Hah/BioMed Central Ltd/CC BY 2.0)
Scientists consequently decided to retroactively reconstruct the 11-year Schwabe cycle beyond 400 years in an attempt to understand how they fit together.
This was achieved by uncovering solar evidence stored inside trees, in the form of radionuclides.
Laboratory of Ion Beam Physics researchers led by Professor Dr Hans-Arno Synal and Dr Lukas Wacker traced the Schwabe cycle to the year 969 by measuring radioactive carbon concentrations in tree rings.
Because trees grow in an annual cycle, they create a compelling visual time capsule of the Sun's annual output.
Solar mystery: The Sun's cadence has been studied for four centuries (Image: Robert A. Rohde/Global Warming Act/CC BY-SA 3.0)Insurance Loans Mortgage Attorney Credit Lawyer
Compiling those rings, therefore, creates a sophisticated picture of solar activity, with each ring containing a trace amount of radioactive carbon - as