The temperature of our nearest star is not uniform and varies considerably. At the core of the sun, gravitational attraction produces enormous pressure and temperature, which can reach 15 million degrees Celsius. Hydrogen atoms shrink and merge, creating helium. This process is called a thermonuclear reaction.
The thermonuclear reaction produces huge amounts of energy. Energy comes to the surface of the sun, the atmosphere and beyond. From the core, energy moves to the radiation zone, where it spends up to 1 million years, and then moves to the convective zone, the upper layer of the inner part of the Sun. The temperature here falls below 2 million degrees Celsius. Huge bubbles of hot plasma form a “soup” of ionized atoms and move upward toward the photosphere.
The temperature in the photosphere is almost 5.5 thousand degrees Celsius. Here, solar radiation becomes visible light. Sunspots on the photosphere are colder and darker than in the surrounding area. In the center of large sunspots the temperature can drop to several thousand degrees Celsius.
The chromosphere, the next layer of the solar atmosphere, is slightly colder – 4320 degrees. According to the National Solar Observatory, the chromosphere literally means “color sphere”. Visible light from the chromosphere is usually too weak to be visible against a background of a brighter photosphere, but during total solar eclipses, when the moon covers the photosphere, the chromosphere is visible as a red rim around the Sun.
“The chromosphere seems red because of the huge amount of hydrogen in it,” the National Solar Observatory wrote on its website.
The temperature rises significantly in the corona, which can also be seen during an eclipse, when the plasma flows upward. The crown can be surprisingly hot compared to the body of the sun. The temperature varies from 1 million degrees to 10 million degrees Celsius.
When the corona cools down, losing heat and radiation, the substance is blown out in the form of a solar wind, which sometimes intersects with the Earth.
The sun is the largest and most massive object in the solar system. It is located in 149.5 million km from the Earth. This distance is called an astronomical unit and is used to measure distances throughout the entire solar system. Sunlight and heat take about 8 minutes to fly to our planet, so there is another way to determine the distance to the sun – 8 light minutes.