Just a few weeks back the Sun was peppered with sunspots- dark areas stretching thousands of kilometers across that come and go. This was hardly surprising given that it is currently in the middle of its solar maximum- the most active period in the Sun’s 11-year cycle. But in an image taken last Thursday by NASA’s Solar Dynamics Observatory there was not a spot in sight. A day later, one lonely sunspot seemed to be making an appearance, and scientists aren’t quite sure why the Sun is displaying this peculiarly quiet behavior.

According to solar physicist Tony Phillips, while this observation is out of the ordinary, the solar maximum we are currently experiencing is the weakest one for a century.

“It’s weird, but it’s not super weird,” Phillips told LA Times. “It all underlines that solar physicists really don’t know what the heck is happening on the Sun. We just don’t know how to predict the Sun, that is the take away message of this event.”

Sunspots are caused by extremely strong magnetic fields that cause magnetic pressure to increase in an area while the surrounding atmospheric pressure decreases. This then causes a slight drop in temperature as the concentrated magnetic field prevents hot gas flowing from the Sun’s interior to the surface. Sunspots often occur in pairs with the magnetic field pouring out of one and entering the other.

Sometimes the magnetic fields can become twisted, resulting in a huge build-up of energy and massive explosions on the photosphere. These explosions are called Coronal Mass Ejections and solar flares. When sunspots are particularly active, resulting in numerous solar flares, geomagnetic storm activity is increased and we see spectacular Northern and Southern Lights.

As Alex Young, a heliophysicist at NASA’s Goddard Space Flight Center, points out, it’s difficult to know what can be classed as “normal” behavior from the Sun given that we’ve only been intensively studying it for the last 50 odd years; a speck on its 4.5 billion year history.

As it stands, whether or not this quiet period will continue for an extended period of time remains unknown and highlights the unpredictable nature of our Sun.

[Via LA Times]