The coronal hole is an area where the solar wind is streaming out of the Sun at superfast speeds, researchers said.
NASA's Solar Dynamics Observatory (SDO) has captured a video of the Sun's square-shaped coronal hole last week, 'Space.com' reported.
The coronal hole appears dark because there is less material emitting light in the ultraviolet range of the spectrum used to make the video, NASA astronomers said in a video description.
"Inside the coronal hole you can see bright loops where the hot plasma outlines little pieces of the solar magnetic field sticking above the surface," they said.
"Because it is positioned so far south on the Sun, there is less chance that the solar wind stream will impact us here on Earth," they added.
According to Tech Times, coronal holes come in a wide variety of shapes and sizes, including this square example. There is no single reason why this feature formed in this particular shape.