The Spotless Sun

Since the start of 2017, only a single small sunspot has made a brief appearance on the solar disk.

The photosphere as seen by NASA's Solar Dynamics Observatory

The Sun's spotless photosphere as seen on January 12, 2017, by the Solar Dynamics Observatory.
NASA / SDO

Although 2017 heralds the first total solar eclipse to be seen from the continental U.S. in more than 30 years, the Sun itself has become a featureless ball — at least in visible wavelengths. Following the weakest solar cycle in more than 100 years, the minimum of Cycle 24 appears to have arrived for the duration, at least for observers.

According to Tony Phillips of SpaceWeather.com, the Sun hasn't been blank for so long since May 2010. Only a single tiny sunspot briefly appeared then vanished on January 3rd, followed by a continuing stretch of spotless days.

Even the usually dynamic chromosphere visible at the wavelength of hydrogen alpha is nearly as featureless, with only several tiny prominences visible along the solar limb.

The Sun in hydrogen-apha light.

The Sun as it appeared today in hydrogen-alpha light.
NSO / GONG

Long-time Sky & Telescope contributor Tom Fleming notes that this is the first spotless week following a steady decline throughout the last half of 2016.

But not to worry, the situation can change very suddenly. NASA's STEREO A spacecraft, which monitors the Sun from a point ahead of us along Earth's orbit and sees a good portion of the solar disk that has recently disappeared from our view, shows an active region on the Sun's far side. This region should come around and be visible in about a week or so, assuming it doesn't dissipate.

And just because there are no sunspots doesn't mean the Sun is completely inactive. The solar wind buffeted Earth's magnetosphere several days ago, producing aurora activity near the Arctic Circle. Although no coronal holes are expected to face Earth in the coming days, that too can change.

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