sentences:  A planet about 150 light years away from earth, HD 209458 b was known previously to contain an evaporating hydrogen atmosphere, along with oxygen and carbon.Though the planet is only 7 million kilometers away from its star, the planet is not hot enough to break the water molecules.HD 209458 b, a transiting planet, passes in front of its star, where it can be viewed from earth every three and a half days.