The Sun… idolatrized from ancient civilizations people to 60s rock legends, its presence has been acquainted by humanity from early ages, providing it a godlike status, or even dedicated celebrations of its “prevalence against darkness”. This big ball of plasma has always been there for us, and, as dangerous as it can be extended unprotected exposures to it, all the biodiversity and life we are presented with, and are part of, in this planet, started with, and still depends on it. The sun is our nearest star, the one we can see the brightest (not recommended to directly staring at it), it’s rays in contact with our skin provide us a natural source of an essential vitamin (D) for our wellbeing. We are a product of the sun!
With all this importance to life as we know it, and for so many years, no wonder that this huge ball of superhot gas spreads across 1.4 million kilometres in diameter, equal to 109 Earths side by side, and has a mass of as much as 330 000 Earths. Overall, inside the Sun fit 1.3 million Earths. The Sun is the largest object in our solar system, with its gravity holding the solar system together, with every object, from the biggest planets, to the smallest bits of debris, orbiting around it. Nevertheless, in comparison to other stars found throughout the universe, the sun is an average star in terms of its size, thus fitting in the category of a yellow dwarf star.
The sun’s formation dates back to 4.6 billion years ago, in a giant, spinning cloud of gas and dust called solar nebula. Once the nebula collapsed under its own gravity, most of the nebula’s material was pulled towards the center to form the sun. The sun accounts for 99.8% of our solar system’s mass, with the remaining material of the nebula having been transformed into planets and other objects that now orbit the Sun. It is predicted by scientists that the sun will still last 5 more billion years, before it turns into a white dwarf.
Although it looks static, the sun is a dynamic ball of hydrogen and helium, held together by its own gravity. It is composed by many layers, as depicted in Figure 1. The hottest part of the Sun is its core, with temperatures reaching 15 million oC. Although the Sun doesn’t have a solid surface like other rocky planets and moons, what is thought of as its surface is designated as the photosphere. The photosphere is much cooler than the Sun’s core, reaching temperatures of about 5500 oC. One of the biggest mysteries about the Sun is the reason why the Sun’s corona, an outter layer compared to the photosphere, is much hotter than the layers below it.
Regarding its activity, the sun doesn’t always behave the same way, going through phases of high and low activity that make up what’s called the solar cycle. What happens is that every 11 years, the Sun’s geographic poles swap their magnetic polarity, and the Sun’s photosphere and corona, e.g., change their activity from quiet to agressively active. When the solar maximum is reached, sunspots, solar flares , and CMEs (coronal mass ejections) become common. The next predicted maximum by scientists will be in July 2025, and as we are approaching that date, these kind of extreme events become more observable and felt for and by us, on Earth, like they were in May 2024.
