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The Sun

The Sun is the largest object in the solar system with a central temperature of 16 million degrees. It is located at the centre of the solar system. It is about 4.5 billion years old.

The source of the Sun's energy is the nuclear fusion reaction of four hydrogen atoms fusing together to become one helium atom.

 

What will happen when all the hydrogen in the Sun's core has been transformed into helium?

The Sun will expand to a red giant which fuses helium to carbon and oxygen in its core by the Triple Alpha Process.

After the helium in its core is used up, the Sun will shed its atmosphere and in the process create a Planetary Nebulae. A planetary nebulae is a discharge consisting of luminous shells of gas and plasma ejected by stars like our Sun at the end of their lives.

During this process, the remnant central core of the Sun will become a white dwarf. It will have a temperature of about 20,000 degrees. However, as it will no longer have any source of energy, it will slowly cool down.

 

How bright will the Sun be when it becomes a white dwarf?

During this time, the Sun's light will be 100 times dimmer than it is now. Daytime will be colder because there will be less heat energy released by the white dwarf.

 

What will be the temperature of the Earth when the Sun becomes a white dwarf?

The Earth is going to have a temperature of about 90 K (-183 °C).
(For more information on the temperature of the future Earth, go to Earth's page).

 

For this planet's panel in the model click here

Click here for a planetary nebula at the Astronomy picture of the day

Click here for the Wikipedia entry on the Sun

For a link to "The Life of the Sun" click here