Starbirth. Computer illustration of a newborn star (upper left) shining through the nebula from which it was formed. The new star's solar wind is blowing a hole in the surrounding gas. Stars form from clouds of gas which collapse due to gravitational attraction until the particles are hot and dense enough for nuclear reactions to begin. The energy from these reactions balances the collapse and blows away any remaining material. The gas in the nebula is glowing red as its hydrogen atoms are ionised by the new blast of radiation. These areas are known as emission nebulae, or HII (ionised hydrogen) regions, and many are known.