THE EDGE OF THE SUN Photo: Sergio Castillo

Giant sunspot AR2403 has departed, leaving the face of the sun mostly blank. Amateur astronomer Sergio Castillo of Corona, CA, decided to look for something else to photograph. "My search didn't take long," he says, "because there are plenty of beautiful prominences on the solar limb." This is what he saw on Aug. 29th:

The massive structure is more than 30,000 km tall and 100,000 km wide. Planet Earth could fit through the central arch with room to spare. (Croquette, anyone?)


Prominences are plumes of hot plasma held aloft by magnetic fields on the sun. Typical prominences last a few days, until the underlying magnetic supports become unstable and collapse. This one has already been visible for several days, so a photogenic explosion could be in the offing. Amateur astronomers with solar telescopes and filters are encouraged to monitor developments.