The Spotted Sun
On Oct. 11 and 12, there were no spots visible on the Sun. NASA solar physicist David Hathaway has checked the Sun every day since 1998 and had never seen it free of sunspots.
Now there are several, and the largest one is growing. In this image taken yesterday by the Solar and Heliospheric Observatory, the sunspot group named 687 is about 10 times wider than Earth.
Sunspots are cooler regions on the solar surface. They're areas of intense magnetic activity that are something like caps on a shaken soda bottle. If they blow, they release tremendous amounts of matter and energy into space. These solar eruptions can threaten Earth-orbiting satellites, black out radio communications, and on occasion trip power grids at the surface.
Scientists say sunspot 687 has the potential for medium-class solar flares.
The lack of sunspots earlier this month is a sign that a low point in solar activity may arrive sooner than expected, Hathaway says. Solar activity goes in a cycle that is roughly 11 years long, but it can vary.
"The shortest cycles are 9 years, and the longest ones are about 14 years." Hathaway says. And scientists don't know what causes the variation. "We won't even know if the current cycle is long or short -- until it's over. More on the cycle from Science.NASA.gov.
-- SPACE.com Staff
Credit: SOHO/NASA/ESA
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