Saturday 22 June 2024

Wonder-filled Solar System - Part I


Many people are attracted to diamonds. It's not because diamonds are the hardest substance that everyone has become a fan of hardness. Natural diamonds are rare, which is why they are so expensive. In Bangladesh, the price of one gram of diamond is over four lakh takas. But what if diamonds were constantly raining down from the sky like raindrops, scattered everywhere? That would be unbelievable, or at most, a fantasy. But what if I told you that this is happening on one of the planets in our solar system! Similarly, if someone says that the sun rises in the west, we will naturally think the person is mistaken. But the truth is, the sun does rise in the west on one of the planets in our solar system. On some planets, a day is longer than a year. Sounds astonishing, doesn't it? There are countless astonishing phenomena occurring on the planets and moons of our humble sun. Today, we will discuss a few of these amazing phenomena.

The Sun and Its Family

If our solar system were a family, the head of that family would be the Sun. Its children, the planets, revolve around it. However, calling the planets the Sun's children can be misleading because each of the Sun's planets is as old as the Sun itself—4.5 billion years. Not only that, but the moons orbiting the planets also originated at the same time, making them as old as the Sun too. In this solar family, the father, son, and grandson all share the same age.

So, how many members are there in this family? There are eight planets and a total of 288 moons. In addition, there are dwarf planets, which have eleven moons of their own. As satellite technology advances, new discoveries are continuously increasing the number of solar system members. Despite being the head of such a large family, the Sun is not one of the brightest stars in the universe.

Among the hundreds of billions of stars in the universe, our Sun is a very ordinary G-type star located about 150 million kilometres from Earth. The temperature of a G-type star is about 6,000 degrees Celsius, which gives it its yellow colour. To summarize the size of the Sun: its diameter is 1,390,000 kilometres, which is 108 times that of Earth. This means that to stretch from one end of the Sun to the other, you would need to line up 108 Earths side by side. The volume of the Sun is so vast that 1.2 million Earths could fit inside it. If you combine everything in the solar system except the Sun, the Sun itself is still 750 times larger. The Sun is 333,000 times heavier than Earth, containing 98% of the mass of the entire solar system.

Humans have been observing the Sun since they developed intelligence, which is where the journey of astronomy began. However, even after all these years, many aspects of the Sun remain equally astonishing. For example, the Sun's temperature.

The Temperature of the Sun's Atmosphere is Higher Than Its Surface Temperature

 The Sun has many layers of gas inside it. Although there are no clear boundaries between these layers, each one has a distinct function. The Sun is primarily divided into two parts: the inner part and the outer part. The inner part can be divided into three regions. At the very center is the core. Surrounding the core is the radiative zone. Encircling the radiative zone is the convection zone. The outer part consists of three layers of gas, collectively referred to as the Sun's atmosphere. The innermost layer of this part is the photosphere, which surrounds the convection zone. Encircling the photosphere is the chromosphere. The outermost layer is the corona, which is the Sun’s outer surface.

The core of the Sun is the hottest part, with a temperature of about 15 million degrees Celsius. It occupies about a quarter of the Sun’s volume but holds almost half of its mass due to the dense, hot gas. The core is the source of all the Sun's energy, where nuclear fusion occurs. Every second, four million tons of hydrogen are converted into energy in the Sun's core.

The next layer outside the core is the radiative zone, filled with gamma rays. This region accounts for about a third of the Sun's volume, with temperatures around 5 million degrees Celsius. The energy produced in the core passes through this region in the form of electromagnetic waves. Due to interactions with dense gas, the energy flow here is extremely slow, taking between 30,000 and 100,000 years to move through this zone. Gamma rays are gradually transformed into visible light with longer wavelengths as they move through this region. Once this energy leaves the radiative zone, it takes just 8 minutes and 26 seconds to reach Earth.

Beyond the radiative zone is the convection zone, where the temperature averages around 5,500 degrees Celsius. This zone occupies more than 50% of the Sun's volume. Energy is transported through this zone by the convection of plasma, similar to how hot water rises and cold water sinks in a boiling pot. Energy moves quickly through this region, taking about a week to reach the photosphere.

Since the Sun is not a solid object but a gas giant, it has no solid surface. The "surface" is a 500-kilometer-thick layer of gas called the photosphere, which is what we see when we look at the Sun. Energy from the photosphere is emitted into space as light. The photosphere is very transparent, allowing energy to spread out as heat and light. When we look at the Sun, it appears to be a glowing ball of gas because we can see the convection zone through the photosphere.

Starting from the photosphere is the Sun's atmosphere. The layer immediately above the photosphere is the chromosphere, the innermost layer of the Sun's atmosphere, visible only during a total solar eclipse. The chromosphere's temperature is about 11,000 degrees Celsius. While the Sun's surface temperature is around 5,500 degrees Celsius, the temperature jumps to 11,000 degrees Celsius just 5,000 kilometres above the surface. The surprises don't end there. Moving outward to the corona, the outermost layer of the atmosphere, the temperature skyrockets to about 1.7 million degrees Celsius. What causes this?

Scientists have proposed some hypotheses, but the exact reasons are still unknown. One theory is that plasma moving from the photosphere to the chromosphere increases the temperature. From there, it moves to the outermost layer, raising the temperature by several hundred thousand degrees. Another theory is that the strong magnetic fields in the Sun's atmosphere increase the temperature. It is hoped that the satellite 'Parker,' sent close to the Sun, will help provide accurate explanations for many of the Sun's mysteries.

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