The darker section at the top of the Sun in the above video is a coronal hole – part of the star’s atmosphere where its magnetic field bursts open and spurts streams of solar material out into space.
It appears as a dark “hole” on the surface of the sun because the process makes its atmosphere cooler and less dense than those around it.
The footage was captured between July 13-18 by Nasa’s Solar Dynamics Observatory, a five-year mission aimed at learning more about how “space weather” released by the sun affects astronauts, satellites, other planets and Earth itself.
The coronal hole pictured last month is particularly large, measuring at least 400,000 miles across – more than the width of 50 Earths placed side by side.
Although it looks dark and lifeless it was likely releasing fast solar wind, or streams of charged particles, at up to 500 miles per second.
This is about twice as fast as the normal solar wind, which is constantly being released by the Sun in all directions across the entire Solar System.
Coronal holes were first discovered in the 1970s and their size and number are known to fluctuate in tandem with the Sun’s natural eleven-year cycle.
The holes move closer to the poles of the Sun as it enters the most active phase of its cycle, the solar maximum, which is scheduled for later this year or early 2014.
“While it’s unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere,” Nasa’s Karen Fox said.
Courtesy: Nasa, Esa, Soho