Citations:billion


 * 1997 September 1 — R Naeye. Through the Eyes of Hubble: The Birth, Life and Violent Death of Stars. CRC Press. Page 15.
 * The Sun is slowly fusing its hydrogen reserves into helium. At present, the Sun's core has converted roughly half of its hydrogen into helium. The Sun is almost 5 billion years old, so 5 billion years from now all of the hydrogen in the Sun's core will be gone. This will have grave consequences for the well-being of the Sun and Earth, as we shall see in Chapter 4.