The Sun is a vulgar star, with relatively little mass, so it will end its days expanding and transforming into a red giant, and then expelling its outer layers into the stellar medium and remaining in space in the form of a white dwarf.
However, this does not mean that its life is being boring. Even the behavior of medium-sized, gentle stars, such as our Sun, goes through periods of high activity that can cause it to pour more than its usual amount of energy into space. And sometimes it does so abruptly, although we should not be alarmed because even its most ‘aggressive’ reactions are consistent with the natural behavior of a star.
Our Sun is currently going through solar cycle 25, a stage of high activity that, according to astronomers, will reach its maximum peak in mid-2025. Each of these stages usually lasts between 9 and 13 years, and they usually give way to phases characterized by notably lower activity.
The curious thing is that the current cycle is being more vigorous than astronomers had predicted. In fact, on April 20, NASA identified a solar flare of some intensity (although not one of the largest observed by scientists). Astrophysicists predict that this cycle will last approximately eleven years, which is the norm, although it began only two years ago, so it still has many years of activity ahead of it.l
The ‘soul’ of a star resides within it. If we want to understand where it gets its energy from and what mechanisms allow it to maintain its equilibrium, we must necessarily delve into its physics. However, we need not be intimidated; it is possible to understand what phenomena take place in the stellar core without resorting to mathematical calculations. Astrophysicists use them, of course, but we can circumvent them and still become familiar with the physics of stars.
During this stage the star is consuming its hydrogen reserve and producing helium. And along the way it releases a large amount of energy. An interesting note: this is the process we are trying to replicate on Earth thanks to experimental nuclear fusion reactors, such as ITER. This is the mechanism that is currently taking place inside the Sun. It was set in motion when the temperature of the star’s core reached ten million degrees Celsius, and will continue for a part of the star’s life known as the main sequence.
As the hydrogen is consumed, the star is readjusting, compressing its core and increasing its temperature, so that the circumstances are in place for helium ignition to begin. Or not. It will depend on the mass of the star. In any case, the Sun has only consumed about half of its hydrogen reserve, so it has fuel for several billion years more. You can finish your coffee quietly.