The Northern Summer Milky Way is part of our own galaxy seen from the inside. Bright star clouds and dark nebulae line the Milky Way from the constellation of Cygnus at lower left to Cassiopeia at upper right. The large red emission nebulae are star-forming regions. Some are listed in the NGC (New General Catalog) and IC (Index Catalog). Hold your mouse cursor over the image to identify NGC and IC objects within the Milky Way. The red emission nebula are clouds of hydrogen gas that are condensing under gravitational attraction and forming new stars. These hot young stars heat the gas in the nebula causing it to fluoresce and emit light. Dark nebulae are opaque clouds of dust and matter in space that hide the light of stars behind them.