What is the approximate surface temperature of the sun?

The Sun, that extremely luminous object that warms us every day and keeps us connected to all the planets in our solar system, is a yellow dwarf star and is composed of bright gases.

The approximate surface temperature of the Sun is about 5,800 °F or 5,527 °C. Its high temperature, plus the distance we are from the Sun, allows us on Earth to feel an average temperature of about 14 °C, which represents one of the main reasons why there is sustainable life on our planet.

What are the seven layers of the Sun?

The Sun’s seven layers

The Sun is composed of 7 main layers, of which three are internal, and four are external. The inner layers are the core, the radioactive zone, and the convection zone. The external zones are the photosphere, chromosphere, the transition region, and the corona.

Internal layers

Our Sun’s internal layers

Core

The core is a region of the Sun where energy is produced through thermonuclear reactions, creating exceptionally high temperatures, reaching about 15 million degrees Celsius.

Hydrogen is used in these nuclear reactions to form helium. As a result of these reactions, tremendous amounts of energy are released, which move away from the Sun, generating the light and heat that we receive on Earth.

The core, which begins in the center of the Sun, extends to about a quarter of its radius.

Radioactive Zone

This area is located between the core and convection zone. It occupies approximately 70% of the total radius of the Sun. The energy produced in the center by nuclear fusion moves outwards steadily in the form of electromagnetic radiation.

According to scientific studies, approximately 170,000 years must pass for this electromagnetic radiation to pass through the entire radioactive zone.

Convection zone

It is located above the radioactive zone. It extends from a depth of approximately 200,000 kilometers to the visible surface. The estimated temperature in the convection zone is 2 million degrees Celsius.

The energy moves towards the surface of the Sun through convection currents of cold and hot gases. It happens when the radioactive zone’s density becomes very low, and the core energy in the form of light is turned into heat.

The heat from the ends of the radioactive zone increases until it cools down enough to heat up again. This pattern of hot and cold material occurs in the cells of the convection zone.

Outer layers

Photosphere

It is the lowest layer of the Sun, and corresponds to the layer that can be seen directly from the Earth. It is also called “the solar surface.”

Much of this layer is covered by grains caused by bubble-shaped gas escaping from the convection zone and by sunspots created by strong magnetic fields.

The Sun’s granulation is seen in the photosphere, resulting in the appearance of bright cells with dark borders.

The temperature of the photosphere varies between 6,500 °K at the bottom and 4,000 °K at the top.

Chromosphere

It is the surface of the Sun that lies between 250 miles and 1,300 miles above the photosphere. The chromosphere has a temperature that varies between 4,000 °K at the bottom and 8,000 °K at the top.

As a result, in this layer and other upper layers, the temperature increases as it moves away from the Sun, contrasting to the lower layers, where the gases are hotter in the center.

Transition region

This layer is the thinnest, has a size of approximately 60 miles, and is located between the crown and the chromosphere.

In this region, the temperature increases rapidly from about 8,000 °K to 500,000 °K. The scientific community has not yet discovered the causes of this rapid increase in temperature.

What is the Sun’s corona?

The Sun’s corona visible during a total solar eclipse

The corona is the outer atmosphere of the Sun, and it extends for several thousand kilometers above the visible surface of the Sun. This corona changes as it moves away from the Sun, becoming solar winds that flow through our solar system, reaching a speed of 400 kilometers per second.

Its name comes from the shape of the corona formed in a total solar eclipse.

Hotter than the surface of the Sun

Surprisingly, the Sun’s corona has a higher temperature than the surface itself. It is probably due to the magnetic fields that trap the Sun’s corona, raising its temperature to millions of degrees.

The corona has a brightness of about 50% of the moon’s and is generally not visible to the human eye because the brightness of the solar surface obscures its light.

However, when a total eclipse of the Sun occurs, the moon blocks all the light from the photosphere, allowing the human eye to observe the corona’s light emitted.

Scientists use the coronagraph telescope to study the corona, which simulates an eclipse by covering the bright disk of the Sun.

The corona is composed in the same way as the interior of the Sun, mainly of ionized hydrogen. Thus, the corona contains protons and electrons, just like other atoms. The corona emits radiation in the form of X-rays and can only be seen from space.

It is important to emphasize that not all corona escapes from the Sun. That is, not all corona becomes solar winds.

Other stars may also have a corona, which can be detected using X-ray telescopes. Some stellar corona, particularly in young stars, are much more luminous than the corona of our Sun.

The Corona Problem
The corona problem: it’s hotter than the core

One of the most challenging puzzles of our Sun is the so-called crown problem. The corona can reach a temperature of up to 2 million degrees. While the core can reach a temperature of about 15 million degrees, it decreases towards the surface, where it reaches only about 5,000 degrees.

The temperature of the corona should be lower as it moves away from the Sun. However, it increases, changeling humanity’s greatest minds to understand why and how it happens.

Northern Lights (Aurora Borealis)
Northern lights, also known as Aurora Borealis

When the solar wind reaches Earth, our planet’s magnetic field sometimes traps these electrons and protons and pulls them into Earth’s atmosphere. Atoms in the atmosphere interact with these high-energy particles by taking energy from them and releasing energy in the form of light.

This visualization of light is known as the Aurora Borealis and occurs in the northern hemisphere.