Home » For educators » Space Science Experience Introduction » The Rotation of the Sun - http://cesar-tools.cosmos.esa.int/web/index.php?Section=SSE_Sun_Rotation
(Printable version, go to full version)

The Rotation of the Sun

12-14-year-old students

In this experience, we will discover what the Sun is made of and what are the mysteries behind its dark spots, do you want to join us?


The material for the classroom before coming to ESAC can be divided into two parts:

  • For students:
    • Introduction to ESA (6:46 min)
    • Departure into Space (4:02 min)
    • The space missions that observe the Earth  (5:11 min)
    • Paxi - The Solar System (5:18 min)
The Sun is our closest star, at only 150 million kilometers from the Earth. If we compare the Sun with other stars from our Galaxy, the Sun is a standard dwarf star. However, it is 109 times bigger than the Earth !!
Just like other stars, the Sun rotates around itself as well.

Sun rotation animation where flares and prominences are reproduced. Credits: NASA

The Sun is 333.333 times more massive than the Earth.Credits: NASA

The Sun is a big ball of gas and plasma with an onion-like internal structure as it is shown below. The center of the star is around 15.000.000K and it is where the thermonuclear reactions (H into He) take place.

Why is the Sun so hot?

Well, the Sun is continuously collapsing under its own gravity (due to its mass) which creates a region of very high pressures and temperatures that initiate thermonuclear reactions. 


Did you know that it takes hundreds of thousands of years for the light to travel from the center of the Sun to its surface? However, it takes only 8 minutes for the light to travel from the surface of the Sun to the Earth.

The Sun's surface can be divided into three main regions: the photosphere, the chromosphere, and the corona.

  • The photosphere is the region of the Sun that we see with our eyes. This region has a temperature of about 6000 K. It is in this region where we see the "sun-spots" which are darker because they are cooler  (~1000 K lower temperature).
  • The chromosphere is a thin layer on top of the photosphere at a temperature of about 10.000 K.
  • The corona, together with the chromosphere, forms the Sun's atmosphere. This region is at a temperature of about 2 million K.

Sunspot complex, called Active Region 1967, which extends 180.000 km across (larger than the Jupiter planet). A Smaller group of sunspots also rotating above. Credits: WIRED


Size comparison of a "sun spot" with the Earth  ( bottom right).


By studying the movement of the "sun spots" we can study the rotation of the Sun. Do you want to try?