Science still can't say with certainly anything about the fireball that our civilization has observed and celebrated like a deity for the longest time. There are many theories about how the Sun works, but there is so little reliable data to examine them. The star that shines so peacefully and cruelly from the blue sky is actually hellish world - a great "heater" of humanity, but also a great threat. Its light and energy enable life on Earth, but the charged particles that it randomly emits are a danger to the technologies we have, and thus to our well-being. That is why it is crucial to understand the Sun. That is exactly why two new spacecrafts headed towards it: the American "Parker Solar Probe" and the European "Solar Orbiter". launched in February this year. The Sun is 15 million kilometers away from the Earth. The light takes about 8 minutes to cross that path, the fastest particles of the solar wind 15 hours, the "Concord" plane, theoretically, would take eight years, and the "Solar Orbiter" should - after a few loops - reach its orbit around the Sun after three and a half year. They should get closer to the Sun before than any before, to capture the most detailed images of our star and measure values that will help scientists understand its nature.

So far, more then ten spacecrafts have been sent to the Sun. Some studied the activities of the star, others the material. They provided the scientists with pieces of the puzzle, but not a clear overall picture. That is why there are many contradictory and difficult to prove theories about the Sun, as well as many questions: what drives into chaotic magnetic field? How is the corona heated? Why are the solar winds and storms are so fierce?

The only that certain is that the event inside the Sun are very complex. Hell conditions prevail deep in the star: temperatures reached 15 million degrees Celsius, and the pressure is up to 200 billion times higher that in the Earth's atmosphere. Even the basic building blocks of the Sun, hydrogen atoms, can't withstand that hell, and they break down into positively charged nuclei and negative electrons, creating plasma. But this condition doesn't last long: due to enormous pressure, the protons merge to form helium. The released heat seeks to come to the surface, and further into space. However, in a densely charged ball of plasma this isn't so easy. Energy packets are struggling to break through and take about 170,000 light years to reach the outer, sparse layers from the core. There, in so-called "convection zone", the plasma can still move freely at 2 million degrees Celsius, rise to the surface, cool down and finally sink back into the depths, ending its turbulent cycle.

The secrets of the Sun

This is exactly one of the biggest secrets that the Sun hides. As the charged particles move, a magnetic field in the plasma propagates inside the star far into space. Because the plasma is constantly stirred as the star's rotation rises and falls, the star's magnetic field is extremely complex. The knots on it are constantly splitting and re-creating.

"Without such a opposing magnetic field, the Sun would be a pretty boring star", said Sami Solaki, a helio-physicist and the director of the "Max Plank" Institute's solar system reaching department in Gottingen. Fifteen years ago, astrophysicists believed that the picture was a quite clear - a magnetic field is created at the boundary between dense layers of plasma, at the place where the Sun stops rotating like a solid body, but does so like gas bubbles. But after new data from various aircraft, everything is much less clear today.

The main obstacle in the research is that it isn't possible to peer into the Sun, it is impossible to drill or record it with X-rays, because it is too big and too dense, and everything depends on indirect measurements. Important data will be provided by recording seismic movements, since earthquake waves give indications of temperature, disturbance and changes in density inside the star. The image of the interior of the Sun obtained in this way has so far been confusing, full of turbulence and parts that rotate at different speeds.

Parts of our star visible from the outside also confuse our scientists. Just above the convection zone, on the surface of the Sun, temperatures of about 6000 degrees Celsius were measured. However, at higher altitudes, in the "corona", the temperatures rises sharply and reaches several million degrees Celsius. This means that the surface of the sun looks different from, for example, a stove that is always warmer that the room in which it is. What is it that heats the "corona"?

"It's a little embarrassing that we discovered this phenomenon more than a year ago, but we still can't explain it, that is, there are several different explanations, none of which we can prove", says Solanki.

Maybe that mysterious heating of the corona has something to do with ejection of a huge amount of matter into space - the solar flares. The largest of these eruptions contain billions of tons of charged particles and are so large that they can be observed from Earth, but there are certainly much smaller eruptions across the surface of the Sun that Sam Crucker, a helio-physicist at the University of Applied Sciences in northwestern Switzerland, calls "nanoflares". He believes that their action is due to the heating of the corona. They could release enough energy to build up in the corona. While the calculations sounds promising, Crucker warns:

"We aren't yet able to see these nanoeruptions and confirm that they exist at all."

There is another riddle about the corona: The solar wind - the flow of positively and negatively charged plasma that are constantly flowing from the star into space.

The German astrophysicist Ludwig Birman predicted its existence in the fifties of the last century, since he noticed that the Sun always rotate the tails of comets. Seventy years later, scientists believe that the wind drives a magnetic field. However, it is not yet completely clear what accelerates these particles and why the solar winds sometimes blow at a speed of a million and sometimes at three millions kilometers per hour.

On the other hand, huge eruptions are much more dangerous than winds. The fastest-charged particles emitted by the sun have a speed of ten million kilometers per hour and can wreck havoc on Earth: irreparably damaging satellites, disrupting radio and GPS signals and endangering planes, or loading networks, raising voltage in them and causing hour of electricity disappearance. One such geomagnetic storm caused a power outage in Quebec in 1989 that lasted for several hours.

Literature and images: Politica's Entertainer, number 3582, rubric "Assignments for 21. century"