The sun has gone quiet. Almost too quiet.
A few weeks ago it was teeming with sunspots, as you would expect since we are supposed to be in the middle of solar maximum -- the time in the sun's 11-year cycle when it is the most active.
But now, there is hardly a sunspot in sight. In an image taken Friday by NASA's Solar Dynamics Observatory, a tiny smidgen of brown just right of center can be seen where a small sunspot appears to be developing. Just one day before, there was nothing. It was a totally spotless day.
So what's going on here? Is the "all quiet event" as solar physicist Tony Phillips dubbed it, a big deal, or not?
"It is weird, but it's not super weird," said Phillips, who writes about solar activity on his web site SpaceWeather.com. "To have a spotless day during solar maximum is odd, but then again, this solar maximum we are in has been very wimpy."
Phillips notes that this is the weakest solar maximum to have been observed in the space age. It is shaking out to be the weakest one in 100 years.
"It all underlines that solar physicists really don't know what the heck is happening on the sun," Phillips said. "We just don't know how to predict the sun. That is the takeaway message."
Sunspots are the region of the sun where solar activity originates. This includes solar flares -- giant flashes of light -- and coronal mass ejections when material from the sun goes shooting off into space.
They are caused by highly concentrated magnetic fields that are slightly cooler than the sun, which is why they appear dark to us. Solar flares and coronal mass ejections occur when the fields' energy is released in a very explosive way.
Alex Young, a heliophysicist at Goddard Space Flight Center, said it is hard to say what is and isn't unusual when it comes to the sun.
"We've only been observing the sun in lots of detail in the past 50 years," he said.
"That's not that long considering it's been around for 4.5 billion years."