The Sun has a lot of gas.
From http://www.enchantedlearning.com/subjects/astronomy/sun/sunsize.shtml, I found these facts:
The Sun's mass is roughly 1.99 x 1030 kg. This is about 333,000 times the mass of the Earth. The Sun contains 99.8% of all of the mass of the Solar System.
The sun will blow up in a way - it will shed its outermost atmosphere when it becomes a red giant. This atmosphere will extend out and away from the Sun, engulfing the Earth and the other planets in the solar system. At this point then one could say that the Sun's extreme heat will flood Earth. But this won't happen for another 5 billion years, so we don't have to worry about it at this point in time!
Laura