SEPTEMBER/OCTOBER 2019 •SKYNEWS 9
T
HE SUN HAS GONE QUIET. These days, sunspots (cool, dark regions on the solar
surface that form where magnetic fields are particularly strong) rarely darken its face.
During the past 18 months, the Sun has been spotless some 60 percent of the time. This was
not unexpected. Solar activity goes through peaks and valleys over an 11-year cycle, and it’s
currently in the depths of what’s called sunspot minimum. So when might the Sun become
energetic again?
At the June meeting of the American Astronomical Society, two slightly different opin-
ions were offered. Robert Leamon of the University of Maryland and NASA’s God dard
Space Flight Center believes that Cycle 24 (the current one) will end around April 2020.
Leamon and his collaborators think the next cycle “will be of similar magnitude to
Cycle 24, which is still low by historical standards.” Irina Kitiashvili of NASA’s Ames
Research Center and her colleagues agree that the next solar cycle will begin in 2020, but
they predict the upcoming maximum will be 30 to 50 percent lower than Cycle 24, making
Cycle 25 the weakest of the past 200 years.
Two months earlier, at a space weather workshop hosted by the National Oceanic
and Atmospheric Administration, panel co chair Lisa Upton of Space Systems Research
Corporation summarized the results: “We expect Cycle 25 will be very similar to
Cycle 24, another fairly weak maximum.” The workshop consensus is for Cycle 25
to begin between mid-2019 and late 2020, reaching its height between 2023 and 2026,
the top sunspot numbers ranging between 95 and 130. Since Cycle 24 peaked at 82
sunspots in 2014, this prediction of higher numbers contradicts Kitiashvili’s bleaker fore-
cast. Another contradictory forecast comes from Scott McIntosh of the High Altitude
Ob servatory, in Colorado, who argues for a peak of 155 sunspots in mid-2023. Because
solar scientists are unable to agree on the strength of the upcoming cycle, observers can
do little more than wait and watch. ✦
O SUNSPOTS, WHERE ART THOU?
REMEMBER THESE?A gigantic sunspot, almost 130,000 kilometres across, was photo graphed
by SkyNewseditor Gary Seronik during the partial solar eclipse on October 23, 2014, near the peak
of Cycle 24. This active region was one of the largest of the current solar cycle.