Black Hole Sun by National Geographic

Black Hole Sun

Image courtesy SDO/NASA

The sun appeared to have a bald spot for a few days in early February, as a massive coronal hole was aimed at Earth. Seen in extreme ultraviolet by NASA's Solar Dynamics Observatory, or SDO, the dark hole stretched across the top of the sun on February 1.

Coronal holes are magnetically open regions on the sun that send out streams of high-speed charged particles. As SDO watched, this coronal hole rotated to face Earth, increasing the chance for aurora sightings.
(See pictures: "Huge Solar Storm Triggers Unusual Auroras.")

Published February 10, 2011