NASA's Solar Dynamics Observatory observed a massive coronal hole on Monday.
Coronal holes are cooler than other parts of the sun, thus they light less and seem black.
"The large coronal hole right now is around 300,000 to 400,000 kilometres broad,"
NASA Goddard's Heliophysics Science Division associate director for science Alex Young told Insider via email.
"That's 20-30 Earths." Nothing uncommon here," said solar scientist and
deputy director of the National Center for Atmospheric Research Scott McIntosh.
McIntosh labelled these holes "the 'black side' of solar activity" and "not widely understood."