Introduction
The Solar System, our home in the Universe, is made up of an amazing variety of planets, and other objects, that orbit around our local star - the Sun. But what makes the Sun so special, to be considered the center of the Solar System? How has the Sun enabled the formation of planets and the evolution of life on Earth? In this article, we will explore the why and how of our parent star, the Sun.
What Is The Sun?
The Sun is an ordinary but brilliant yellow-white star that is about 93 million miles (150 million kilometers) from our planet. It is the star at the center of our Solar System and the source of light and heat for life on Earth. It is often referred to as our "parent star", and it is appropriately named, since it provides the energy that allows a four-billion-year-long cycle of life to exist on our planet.
The Sun is made of mostly hydrogen and helium gases, which form a glowing ball of gas powered by nuclear fusion. Fusion is the process where several lightweight atoms are combined to form a heavier atom, releasing energy in the process. This is the source of the Sun's immense power and brilliance. The Sun's enormous mass - having 330,000 times the mass of Earth - causes it to produce a strong gravitational pull, which is what keeps the planets and other objects in the Solar System in orbit.
How Was The Sun Formed?
It is believed that the Sun formed about 4.6 billion years ago from an interstellar cloud of gas and dust. At first, the gases within the cloud were drawn together by gravity to form a rotating disk of material known as a proto-planetary disk. This material was swirling around and cooling down, and eventually drew together, collapsing in on itself and forming our Sun. At the time, the Sun was about 40% of its current size - and, it was likely much hotter than it is today.
As the proto-planetary disk was drawn together to form a star, radioactive and chemical elements, such as carbon, oxygen, nitrogen, and iron, also became concentrated in the material, which would eventually become the planets, moons, asteroids, and other objects in the Solar System.
The Sun's Role in the Water Cycle
The Sun's major role in our Solar System is to provide the energy that drives Earth's water cycle, which is vital to all life on the planet. Water cycles between liquid, solid (ice), and gaseous (vapor) states and circulates through the atmosphere, hydrosphere, and lithosphere of Earth.
The Earth is constantly being heated by the Sun's energy - which causes the liquid water in oceans, rivers, and lakes to evaporate and rise up as water vapor in the atmosphere. As the water vapor rises and cools, it condenses and forms clouds. Eventually, the clouds become so heavy that their contents are forced back to the Earth's surface, usually in the form of rain, snow, or hail. This water eventually flows from the Earth's surface back into the ocean and the cycle starts all over again.
This cycle is incredibly important - it makes water available to plants and animals, which need it to survive; it cleans our atmosphere by trapping pollutants, which are eventually washed back to the ground (this is why it often rains after a very polluted day); and it moderates the temperature on Earth as colder water evaporates and forms clouds (without clouds, temperatures on our planet would be much higher).
The Sun's Role in the Formation of Life
The Sun's energy plays a pivotal role in another important way - the formation of life on Earth. Photosynthesis, the process by which plants use the Sun's energy to convert carbon dioxide and water into food, is the backbone of life on Earth. This process uses light from the Sun to create sugars, which are a form of energy stored in plants. These plants then release oxygen into the atmosphere.
This oxygen helps create the ozone layer, which is a layer in the Earth's atmosphere that acts as a shield against the harmful ultra-violet radiation that the Sun emits. Without the ozone layer, Earth's surface would be too dangerous for life. As the Sun continues to warm the surface of the Earth and produces light, it gives energy to the plants, which they use to grow and reproduce.
The Sun as a Timekeeper
The Sun is used as the main reference point in defining the passage of time on Earth. Day and night occur due to the rotation of the Earth's axis in relation to the Sun - we experience this as the Sun rising and setting every day. The length of a year is determined by the time it takes for the Earth to complete its orbit around the Sun. This is why the length of a day and a year vary depending on where on the Earth's surface you are - closer to the equator you are, the shorter the day. And, since the Earth's orbit around the Sun is slightly elliptical, the time it takes for the Earth to go around it is slightly different for each individual year, but the Sun is still our main reference point for the passage of time.
The Sun in Other Cultures
The Sun has long been worshiped or held in high regard in many cultures due to its importance in providing essential life-sustaining energy to our planet. Ancient Egyptians associated the Sun with the god Ra. In India, the Sun is an important part of the Hindu religion and it is worshiped as the creator god of energy, life and knowledge. In many cultures, the Sun is seen as a powerful and life-giving symbol and is often given special rituals.
Conclusion
The Sun is our parent star - it provides the energy and light that let life exist on Earth. Its immense mass, created by the fusion of hydrogen and helium atoms, creates a strong gravitational pull that helps keep the planets of the Solar System in orbit. Its energy also drives the water cycle, which provides water for life, as well as the formation of the ozone layer which protects us from harmful ultra-violet radiation. It even serves as a timekeeper for us, with day and night determined by the rotation of the Earth and the length of a year by the time it takes for the Earth to orbit the Sun. Clearly, the Sun is an integral part of the Solar System and has been a source of awe and reverence in many cultures.