What is the hole in the sun? Phenomenon explained

Coronal hole observed in 2020 (Nasa via Reuters)
Coronal hole observed in 2020 (Nasa via Reuters)

A coronal hole has opened in the sun's atmosphere, a recent photo from Nasa's Solar Dynamics Observatory has shown.

The captured image depicts a stream of solar wind hurtling towards Earth as magnetic fields open up, allowing solar wind to escape. The structure shown spans roughly 800,000 km along the axis.

The hole, which is a region in the sun's atmosphere, was seen on Monday (December 4) according to Space Weather, the US government's official source for space weather forecasts.

It looks dark in the photo because the hot glowing gas (or plasma) normally contained in that area is missing.

But is it really a hole?

Coronal hole and solar wind (Space Weather / Atmospheric Imaging Assembly)
Coronal hole and solar wind (Space Weather / Atmospheric Imaging Assembly)

Coronal holes are not holes in the sun but rather those at the sun's surface. They are a relatively common feature of the sun’s outer atmosphere, called the 'corona'.These holes are large dark regions in the solar atmosphere and can generally be seen in extreme ultraviolet (EUV) and X-ray wavelength imagery.Coronal holes can form at any point during the 11-year solar cycle. They are cooler than the surrounding area.

However, they are more prominent when persistent coronal holes form near the Sun's polar regions, or the solar minimum.

What causes coronal holes?

Dean Pesnell, project scientist for Nasa's Solar Dynamics Observatory, told NPR that scientists aren't really sure where coronal holes come from.

"Some people claim that they are the skeleton of old sunspots," he said.

Other scientists say it occurs when the magnetic fields crash into each other, merge, and split, during periods of intense solar activity.

In March, Daniel Verscharen, associate professor in space plasma physics at University College London, said: “Coronal holes are regions from where fast solar wind is launched into space.

“Fast solar wind has speeds of about 700km or 800km per second and is thus almost twice as fast as the average solar wind."

Is a hole in the Sun anything to worry about?

In short, no, they're nothing to worry about.

"A coronal hole is just a big, dark blotch that we see on the sun in our images," explained Dean Pesnell. "We can only see them from space because, when we look at them [through] a regular telescope, they don't appear."

Are coronal holes common?

Spotting coronal holes is not something entirely unusual. Scientists in March spotted one.

Scientists in March also reported being in the midst of heightened solar activity, as a hole 20 times larger than Earth was spotted. They predicted an increase in the number of phenomena, including coronal mass ejections, geomagnetic storms, and flares.

It has been thought that more coronal holes will be spotted in the coming years.