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The Dark Side of the Sun

  • February 15, 2024
  • 7 min read
The Dark Side of the Sun

On the 8th April 2024, one of the most spectacular solar eclipses of our time will cross North America. Nothing like it will be seen again for another 20 years! The moon’s orbit at this time puts it relatively close to Earth, meaning that it will appear larger, block out the sun’s light for longer and create a darker eclipse than has been seen in decades. Totality – when the moon completely blocks out the sun’s disc – will last nearly four and a half minutes. At this point observers can see the outermost layer of the sun’s atmosphere — the corona — with the naked eye. This is great news for scientists aiming to uncover the inner workings of our star.

The very fact we get to see eclipses at all is incredibly fortunate. We happen to have a Moon that’s just the right size and distance from Earth, and to be in precisely the right orbit around the Sun at this moment in history (considering that these factors change over millions of years), enabling us to witness solar eclipses! However, in the future, as the Moon moves farther away from Earth, it will gradually cease to fully eclipse the sun.

The sun is often thought of as a celestial giver of life, which of course it is, however there is a darker, more sinister side to its powers. Every 11 years the Sun goes through a cycle of activity driven by its magnetic field. The peak of this, known as the solar maximum, is indicated by increased frequency and intensity of visible sunspots on the surface. Sunspots are dark, planet-size regions of strong magnetic fields on the surface of the sun, that can cause solar flares and coronal mass ejections (CMEs). 2024 is set to be the most intense maximum in two decades. What this means for the eclipse is that we get to see an incredible show of bright, petal-like streamers of plasma extending out from the sun’s outer atmosphere. There will also be a higher chance of a CME, a large explosion of hot gas trapped in a loop of magnetic field that is blasted away from the sun’s surface. When these solar eruptions head in the direction of the Earth, the fast solar winds accompanying them can potentially disrupt communications, power grids, satellites and even astronauts in orbit around Earth. These winds seem to be accelerated by kinks that develop in magnetic field near the surface of the sun. This eclipse is a fantastic opportunity for scientists to gain a deeper insight into this phenomena. An accurate prediction of solar wind conditions will be essential in protecting Earth’s technology from any harmful effects and in the development of more robust technology that can better withstand any CME. Luckily for us, Earth’s atmosphere protects us from most of the Sun’s harmful rays. This can be seen in the aurora borealis or australis (in the southern hemisphere). These lights in the sky are high energy particles of solar wind being deflected by our magnetic field. During the solar maximum there is a higher chance of seeing the Northern or Southern Lights further away from the Poles than normal. You can find out more on space weather and aurora forecasts at the Met Office.

We can use Mars as a comparative of what could have happened to Earth without our atmosphere. There is geological evidence that Mars once had liquid water, in fact the Mars Trace Gas Orbiter has identified sub surface iced water, which is the main reason why the Perseverance Rover has been sent to collect samples to look for signs of extinct life, which will indicate a life-sustaining atmosphere at some point in the early history of Mars. It is possible that Mars was too small to keep the dynamo going at its core, as Earth does, and so lost its magnetic field. This meant the atmosphere and liquid water were gradually stripped away, the temperature plummeted and the planet was exposed to the ravaging solar winds.

Knowing the speeds of these winds can help scientists predict when they will reach Earth and develop technology to mitigate some of the potential damage. In the 2020 BBC TV series, COBRA, A massive solar flare strikes Europe, blowing the electric grid and navigational systems, leaving much of Great Britain without power and creating social and political chaos. Although these exact circumstances are fantastical, it does highlight the need to ensure future technology can withstand these flares. The Solar Orbiter, the most complex scientific laboratory ever to have been sent to the Sun and built by Airbus Defence and Space in the UK is giving us greater insights into the Sun’s atmosphere, which you can only see from Earth during solar eclipses.

Understanding space weather will be essential in terms of our ambitions to return to the Moon via the Artemis missions and eventually to send humans to Mars. Such space travellers will be outside Earth’s protective magnetic field, therefore receive much higher doses of ionising radiation from the sun. Over time that could lead to devastating medical conditions, including cancer. Working out how to protect them and how to get early warnings of possible additional solar activity is crucial.

Ingmar Kamalagharan of the UK Space Agency says

“Solar eclipses are an incredible, natural phenomenon that shows in one moment how lucky we are on Earth. We happen to be just in the right time in history and happen to have all the right size objects in the right place to see total solar eclipses. The eclipse itself then reveals the atmosphere of the Sun and the high energy matter that it ejects towards us, which would have destroyed all life on Earth long ago if it wasn’t for our protective magnetic field. Just look at Mars if you want to see how Earth might have ended up! They have shaped our cultures and ideas and have even helped to prove Einstein’s theories, and having seen one in person, you cannot help being affected by the experience.”

The eclipse will begin over the South Pacific and pass over Mexico, the US and Canada, making it accessible to over 50 million people. Varying degrees of the eclipse will be seen across all US states as well as large portions of northwestern Mexico and southeastern Canada.

The promise of a longer, darker, more dramatic eclipse has significantly driven tourism along the 115-mile-wide (185 kilometres) path of totality. According to the Great American Eclipse, up to 4 million people are predicted to descend along this path, making it the biggest travel event of the year.

Major tour operators, museums and local science groups will be offering events, seminars and a host of other fun activities centred around the eclipse. There are even a number of festivals to suit all tastes. Kerrville Eclipse Festival is a free event hosted by NASA. As well as music there will be a number of presentations by scientists to peak your interest. Ground Zero Musicfest is set in a rodeo arena, expect stunt shows, cowboy rodeo, truck shows as well as lots of good music. The Fredericksburg Hot Air Balloon Solar Eclipse Festival gives you a chance to get even closer to the eclipse by viewing it from a hot air balloon. You can even tie the knot at the Total Eclipse of the Heart Festival in Arkansas!

To ensure you will get a front row seat, check the path of totality on this NASA map.

About Author

Natalie Shanahan

Natalie Shanahan has a BSc in Genetics and a MSc in Bioinformatics. She worked as a lecturer, teaching genetics and biochemistry, before moving to Australia to work for their first Bioinformatics company. Here she managed their marketing as well as working on their numerous educational resources. Natalie left her career in science to follow her passion and now works as a personal trainer and nutrition consultant, helping individuals and employees of large organisations, better understand their health and wellbeing.

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