Since Galileo first observed them through his telescope in the early 1600s, sunspots have fascinated scientists. These dark patches on the Sun’s surface can persist for days or even months, but until now, researchers couldn’t fully explain why they remained stable for such extended periods.
A study published in Astronomy & Astrophysics has finally solved this centuries-old puzzle. An international team of scientists, led by researchers from Germany’s Institute of Solar Physics, developed a revolutionary new method for analyzing sunspot stability that reveals the delicate balance keeping these solar features intact.
A group of sunspots, labeled as Active Region 1520 rotated into view over the left side of the sun on July 7, 2012. (Credit : NASA/Goddard Space Flight Centre)
Sunspots are regions where the Sun’s magnetic field is strong, comparable to the magnetic field in a hospital MRI machine, but covering an area larger than Earth itself. These magnetic field concentrations appear as dark spots because they’re cooler than the surrounding solar surface but in reality, a sunspot at the distance of the Sun but isolated from the rest of the disc would shine brighter than the full Moon!
The number of sunspots follows an 11 year cycle, reaching peak activity when solar storms are most likely to occur. During these periods, unstable magnetic configurations near sunspots can trigger explosive events called coronal mass ejections and solar flares. These space weather events can disrupt satellite communications and, in extreme cases, cause power grid failures on Earth.
When observed in white-light coronagraph imagery, CMEs sometimes resemble a light bulb, possessing a bright bulb-like outer shell surrounding a dark void and compact inner structure. (Credit : NASA)
It’s long been suspected that sunspots remain stable because of an equilibrium between gas pressure and magnetic forces. However, proving this balance has been challenging due to atmospheric disturbances that interfere with ground based observations of the Sun’s magnetic field.
The research team made a crucial breakthrough by improving a technique originally developed at Germany’s Max Planck Institute for Solar System Research. Their enhanced method removes the blurring effects of Earth’s atmosphere from observations made with the German GREGOR solar telescope.
Using this refined technique, the researchers analysed polarised light emitted by the Sun to measure magnetic forces within sunspots with unprecedented precision. Their measurements now achieve satellite quality results from ground based telescopes at a fraction of the cost.
The analysis revealed that magnetic forces inside sunspots are perfectly balanced by pressure forces, maintaining strict equilibrium. This delicate balance explains why sunspots can survive for such extended periods on the Sun’s turbulent surface.
This discovery has significant practical applications. By understanding the precise mechanisms that keep sunspots stable, scientists may be able to predict when these solar features become unstable and more likely to produce dangerous space weather events.
Better prediction of solar storms could help protect satellites, power grids, and astronauts from harmful radiation. As our society becomes increasingly dependent on satellite technology and electronic infrastructure, this research provides crucial insights for safeguarding modern life against solar threats. It also represents a major step forward in solar physics, combining advanced ground based observations with sophisticated analysis techniques to solve one of astronomy’s oldest mysteries.
Source : A new method for analyzing the stability of sunspots