A Hole in the Sun

A giant, black region of the sun — called a coronal hole — was spotted on Monday by NASA's Solar Dynamics Observatory.

Despite the name, however, this isn't a physical hole in the solar surface; coronal holes are cooler in temperature, so they don't glow as bright as other areas of the sun and therefore look black.

"The current coronal hole, the big one right now, is about 300,000 to 400,000 kilometers across," Alex Young, the associate director for science at NASA Goddard's Heliophysics Science Division, told Insider over email. "That is about 20-30 Earths lined up back-to-back."

Coronal holes are common; there is "nothing unusual here," Scott McIntosh, a solar physicist and the deputy director of the National Center for Atmospheric Research, told Insider in an email.

Holes like this are part of the sun's normal activity, but McIntosh said that they are "not well understood" and called these events "the 'dark side' of solar activity."

Coronal holes are the source of rapid solar winds, which reach speeds of about 500-800 km per second, Young wrote — The solar winds from this coronal hole are scheduled to reach Earth by the end of this week.  READ MORE...