The Sun has seen a flurry of activity on its surface recently and now Nasa astronomers have spotted not one but two ‘coronal holes’ on our star.

The first ‘hole’ or ‘sunspot’, 30 times the size of the Earth, was spotted earlier this month and led to a severe geomagnetic storm that put satellites on high alert and triggered Northern Lights to very low latitudes.

The most recent hole spotted this week is smaller but still the size of about 18 to 20 Earths across.

The appearance of the latest hole has prompted the US National Oceanic and Atmospheric Administration (NOAA) to issue an alert for an increase in solar wind towards the end of the week, providing another chance for spotting the Northern Lights.

‘Arctic auroras are likely when the solar wind arrives,’ said an alert on Spaceweather.com.

Solar winds can damage satellites at their worst but for people on Earth, they can provide an opportunity to spot stunning auroras.

What is a coronal hole?

Coronal holes aren’t exactly literal holes on the Sun, rather they are large areas that are much cooler than the rest of the Sun, causing them to appear black.

These are places where the Sun’s magnetic field lines don’t close back on themselves, but instead stick straight out into space. This leaves an open channel for solar wind to blast through.

A solar flare is an intense burst of radiation coming from the release of magnetic energy associated with these sunspots.

Flares are our solar system’s largest explosive events. They are seen as bright areas on the Sun and they can last from minutes to hours.

What happens if a solar flare hits the Earth?

That depends largely on what size the solar flare is – nothing may happen at all if they are very small, but larger ones could have catastrophic consequences.

The smallest, C-class, are unlikely to make much impact on Earth, medium-sized ones – known as M-class, could cause some low-level damage, while the largest, known as X-Class, could be seriously disruptive.

The biggest solar flares are known as ‘X-class flares’, which are becoming routine. So far, the Sun has produced seven X-class solar flares this year.

Radiation from the latest flare ionized the top of Earth’s atmosphere, causing a strong shortwave radio blackout over southeast Asia, Australia and New Zealand. 

If you’re hearing a lot about solar flares recently, it’s because the Sun is at its most active. This happens about every 11 years when coronal holes are more likely to appear.

Since December 2019, solar activity, including the number of sunspots and solar flares, has increased.

The Sun is heading to a solar maximum, in 2024, when the star’s polarity will reverse and many more active regions will appear.

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