Shrinking Core of the Sun: Stellar Evolution

Source: Firefly To generate a image for The shrinking core of the Sun is a key part of its stellar evolution

The Sun is a dynamic, ever-changing star, the source of life. But, while this may sound utterly counterintuitive, the Sun is actually shrinking. During its life cycle, hydrogen through nuclear fusion is being converted into helium, a process which contracts the core while the outer layers expand. This, what is called stellar evolution, will eventually transform the Sun into a red giant that engulfs Mercury, Venus, and possibly Earth.

Stellar Evolution – Understanding Stellar evolution describes the life cycles of stars. It is a process energized by nuclear fusion in the core. When stars form out of collapsing clouds of gas and dust, they begin fusing hydrogen into helium, releasing tremendous amounts of energy in the process. This reaction supplies the Sun with its energy and heat.

Hydrogen depletion in the core makes the star shrink due to the gravitational pull. During this shrinking process, the core heats up with increasing density until heavy elements begin to fuse, such as helium into carbon and oxygen. This is then followed by the continued burning of even heavier elements until the star reaches its maximum mass.

The Sun’s Contracting Core

This, in fact, is what the core of the Sun is doing now in its present-day contractions: converting hydrogen into helium that increases the core’s density, thus shrinking. Such shrinkage raises the core temperature and pressure, which in turn accelerates the rate of fusion.

Despite this shrinkage, the outer layers of the Sun itself will actually expand. The reason for this expansion is that the extra energy from the core raises the temperature in the outer layers of the Sun enough that they also heat up and inflate. This inflation will continue until the outer layers of the Sun have expanded to roughly 100 times their present size and have become a red giant. The newly expanded outer layers will then engulf Mercury and Venus, and probably reach the Earth as well.

The Red Giant Phase

Ultimately, once the hydrogen fuel in the core of the Sun will be burned out, helium will start to merge into carbon and oxygen. It will further contract the core of the Sun and greatly expand its outer layers. Then the Sun will go to the red giant phase by becoming a huge, cool, and brilliant star.

At the red giant stage, the outermost layers of the Sun will reach far beyond the Sun’s present surface, even outside the orbit of Venus and probably beyond the orbit of Earth. Whether it will actually be engulfed is not totally certain; although it should be destroyed, there is a chance that it might escape complete destruction.

The Sun’s Future

Source: Wikimedia_Star_Life_Cycle_Chart_By R.N. Bailey – Own work, CC BY 4.0

Eventually, at the end of the red giant phase, the Sun will lose its outer mantle, leaving behind a hot core called a white dwarf-a very compact, extremely dense body composed mainly of carbon and oxygen, in fact. It is so dense that a sugar cube-sized amount of white dwarf material weighs about as much as Mount Everest. The white dwarfs cool over billions of years to black dwarfs.

The Sun’s evolution into a white dwarf marks the end of its main sequence life. The Sun, however, is anything but finished. Billions of years from now, it will eventually degrade into obscurity, a cold and dark shadow of what it once had become.

The Effects of the Sun’s Core Contraction

These roles of the shrinking core of the Sun have large implications for life on Earth and its future. In the phase of the red giant, increased luminosity from the Sun will cause the evaporation of oceans on Earth, along with stripping off the atmosphere. Life may find some other place in the solar system, but eventually the change in the Sun is going to mark great effects on the habitability of our native planet.

This contraction in the core of the Sun does have a bright side, though. The energy output from the core of the Sun is what enables and supports life on Earth. It provides the warmth and light necessary for plants to start photosynthesis-or the conversion of sunlight into energy. Without the Sun’s energy, life as we know it could not exist.

The Shrinkage in the Sun’s Core: Continued Exploration

This phenomenon involves the shrinking core of the Sun, which has strong implications for the fate of our solar system. In the process of conversion of hydrogen into helium, the core of the Sun shrinks and heats up while the outer layers expand. Through this process-which is responsible for stellar evolution-the Sun will be transformed into a red giant, which would engulf Mercury, Venus, and probably Earth.

One of the most fateful developments in the life span of Earth is due to the natural shrinking of the Sun’s core. It will increase its brightness while in the phase of a red giant and cause the evaporation of Earth’s oceans and the stripping of the atmosphere. While this may allow life to find a way onto other planets in the solar system, the change will have a profound impact on the conditions that exist on our home planet.

The Effect of the Sun’s Core Shrinking on Earth

The contracting core of the Sun will greatly raise Earth’s climate. The increase in the luminosity of the Sun will heat up Earth’s temperature even higher. This will thus melt the glaciers and the ice caps, raising the sea levels. Coastal cities and low-lying areas will face flooding, whereas much of the ecosystems will also be disrupted.

Besides the rise in sea level, the growing luminosity of the Sun will also modify Earth’s atmosphere. Due to heating of the planet, the atmosphere will expand, and consequently, the atmospheric pressure will decrease. With the reduction in pressure, the ability of Earth to retain its atmosphere will decrease, potentially resulting in the loss of life-supporting gases.

The Search for Habitable Exoplanets

The future transformation of the Sun into a red giant superclass indicates how vital the search for habitable exoplanets is. An exoplanet is, by definition, those planets that orbit stars outside the Earth’s solar system. Research on exoplanets would enable scientists to learn more about how life exists and where the future of humanity is potentially going to be.

As a result, several exoplanets have been unraveled through the years, some of which seem to be habitable. Being in a habitable zone around a star does not, however, imply the living existence on that planet. The other factors related to the atmospheric composition of a planet and also the availability of liquid water are equally important factors as well.

The Role of Solar Wind in Earth’s Evolution

For the same reasons, core shrinkage will have implications for the solar wind-a stream of charged particles let out by the Sun. The protection of Earth from hostile radiation will also depend on an active solar wind. It generates a magnetic shield that shields the planet from cosmic rays and other deleterious particles.

It can however have adverse effects too. During solar storms, the solar wind’s density and velocity increase that might interfere with and even render useless power supplies and radio communication systems. Moreover, due to the erosion it causes in Earth’s atmosphere, the solar wind can remove potentially life-sustaining gases.

The Sun’s Future: Beyond the Red Giant Phase

The Sun, at the end of the red giant phase, will shed its outer layers and leave behind a hot core called a white dwarf. These are incredibly compact, yet very dense, remnants of carbon and oxygen; they cool over billions of years and eventually, in turn, become black dwarfs.

This change into a white dwarf is the final stage in the evolution of the Sun and can be thought of as the end of its life on the main sequence. But for the Sun, this is anything but the end. Billions of years into the future, it will go out and finally become the cold, dark remnant of its once bright self.

Conclusion

One of the most interesting aspects of stellar evolution has to be the shrinking core of the Sun and its far-reaching ramifications for the future of the solar system. The Sun will only very gradually evolve from a hydrogen-burning star into a helium-burning star as it ages. The core of the Sun is already contracting while the outer layers are expanding, and later the Sun will become a red giant engulfing the inner planets.

While the Sun’s eventual outcome might be bleak, on the other hand, one has to consider the fact that it has already provided our planet with life-giving energy for billions of years. The shrinking core of the Sun forms part of the life cycle that is natural and simply manifestations of the power and beauty of the universe.

Further research into the Sun and its life cycle helps us learn more about our place in the universe and what we might face in the near future. The study of exoplanets and the development of new technologies could someday help us find a home for the human race to continue on and even save our species from extinction.

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