The Sun (will continue) much as it is today until it (enters) its red giant
phase in 4 to 5 billion years. Then, the core (will grow) smaller and hotter
until it finally (finishes) burning the fuel in its nuclear core. When
this (occurs) the core (will become) so dense that helium fusion will begin.
When the helium atoms (will collide), they (will form) carbon from 3 helium atoms
and oxygen from 4 helium atoms. When this process (begins) the Sun
(will produce) enormous amounts of energy. The Sun (will grow) larger as this
energy (increases). It (will be) over a hundred times its present size by the
time it (stops) growing. This is why we use the term red giant. As the
Sun (expands) it is probable that it (will absorb) the Earth. When the Sun
(uses) up all its energy, it (will become) a small white dwarf, and (will not make)
any more energy. After a few billion years, when it (is) completely
cool, it (will be) just a cold dark object.