Anatomy of Sun : Astronomy for Kids

Quick Facts about The Sun :

Sun lies at the heart of our Solar System, where it is by far the largest object of our Solar System, holding 99.85% mass of the entire Solar System, Diameter of Sun is 109 times the diameter of Earth i.e. about one million Earths can fit inside the Sun.

1000000 Earths = 1 Sun

The temperature of Sun ranges from 10,000 Fahrenheit in photosphere, while in the core it is more than 27 million Fahrenheit, driven by nuclear reactions. This is equal to exploding 100 billion tons of dynamite every second to match the energy produced by Sun. It orbits some 25,000 light-years from the galactic core, completing a revolution once every 250 million years or so.

Formation & Evolution of Sun

The sun was born about 4.6 billion years ago. Many scientists think the sun and the rest of the solar system formed from a giant, rotating cloud of gas and dust known as the solar nebula. As the nebula collapsed because of its gravity, it spun faster and flattened into a disk. Most of the material was pulled toward the center to form the sun.

The sun has enough nuclear fuel to stay much as it is now for another 5 billion years. After that, it will swell to become a red giant. Eventually, it will shed its outer layers, and the remaining core will collapse to become a white dwarf. Slowly, this will fade, to enter its final phase as a dim, cool theoretical object sometimes known as a black dwarf.

The Structure of the Sun

Anatomy of Sun

Anatomy of Sun  :

The sun is basically a giant ball of gas and plasma that keeps on getting hotter and denser as we travel from the outer layer to the innermost layer. Temperatures vary from a 5780K on the outer visible layer i.e. photosphere to about 15 million Kelvin in the Core i.e. innermost layer
(0K = – 273°C) .

A Superb Video Reference from Youtube Channel : Crash Course Kids 

Layers of Sun :

1. The Core of Sun

The core of the sun is the actual powerhouse where the nuclear fusion reactions which generates massive amounts of energy takes place. The temperatures at core go upto15 million K, whereas density of core is 160,000 Kg/m3.

2. The Radiative Zone

After the core comes the Radiative zone, which extends upto 70% of the sun’s radius. The energy flowing from the core through the radiative zone, travel in a haphazard path, losing energy in the process.

3. The Convection Zone

The convective zone, like the rest of the Sun, is made up entirely of plasma. A plasma is a ‘gas’ that conducts electrical currents, just like a wire does. The plasma in the convective zone is mainly made up of hydrogen (70% by mass), helium (27.7% by mass) plus small quantities of carbon, nitrogen and oxygen. The bottom of the convection zone is heated by the radiations coming out of the radiative zone. The temperature at the bottom of the convection zone is 200,000° C. At the same time the top of the convection zone (surface of the Sun) is being cooled by the creation of light. The temperature at the surface is only about 5700° C.

4. The Photosphere

The photosphere is the visible surface of the Sun that we are most familiar with. Since the Sun is a ball of gas, this is not a solid surface but is actually a layer which is about 100 km thick (very, very, thin compared to the 700,000 km radius of the Sun). Sunlight as we know it – the visible white light, is emitted from the photosphere. The photosphere is one of the coolest regions of the Sun (about 6000 K), sunspots caused by strong magnetic fields are also visible in the photosphere layer of Sun, because of the distance from the sun to Earth, light reaches our planet in about eight minutes.

Since the sun is a ball of gas with no solid form, different regions rotate at different rates. The sun’s equatorial regions rotate in about 24 days, while the Polar Regions take more than 30 days to make a complete rotation.

A number of features can be observed in the photosphere with a simple telescope (along with a good filter to reduce the intensity of sunlight to safely observable levels).

5. The Chromosphere

The chromosphere is 2000-3000 km thick and the temperature rises from around 6000k to 20,000K. These high temperatures result in hydrogen emitting a reddish light (H-alpha emission) and can be seen in the exciting prominences that project from the sun and in the thin reddish line that can sometimes be seen as a ‘rim’ round the dark disk of the moon inside the corona. It is this colour that gives the chromosphere its name (color-sphere).

6. The Corona

This is the outer layer of the sun and is the whitish halo seen around the disc only during a total solar eclipse. This can be seen in the picture of the solar eclipse above. Temperatures range from 2 to 3 million °.

The Corona of the Sun

The Corona of the Sun : Source