of cold molecular carbon monoxide, the same gas emitted by internal combustion engines on Earth. New stars form within these regions, as gas concentrations collapse under the force of gravity. Although infant stars actually form from molecular and neutral hydrogen gas, these gases are difficult to detect, so astronomers make their observations using the much less common, but more easily detected, carbon monoxide gas shown here.
The Great Nebula and the Horse- head Nebula represent a more- advanced stage of stellar develop- ment. Here young stars have developed enough to shine brightly and heat the surrounding gas and dust. Eventually, radiation from these stars will drive away nearby gas and dust and the stars will
