With no sunspots actively flaring this weekend, solar activity is low. Or is it? There's more to solar activity than sunspots and flares. "I can't recall ever seeing as many magnetic filaments on the sun as I have this month," points out amateur astronomer John W. O'Neal of Amherst, Ohio. "This composite image is my tribute to the filament-ridden sun of May 2015."
Indeed, the sun has been unusually filamentary. Vast strands of plasma held together by magnetic fields have crept across the face of the sun all month long. Occasionally, these dark filaments become unstable and erupt, hurling parts of themselves into space. Fragments falling back to the stellar surface can explode, producing a type of flare called a Hyder flare--no sunspot required.
There is an extra-large filament on the solar disk today. It stretches more than 700,000 km from end to end--about twice the distance from Earth to the moon. These dimensions make it an easy target for backyard solar telescopes.