A billowing cloud of hydrogen in the Triangulum galaxy (Messier 33), about 2.7 million light-years away from Earth, glows with the energy released by hundreds of young, bright stars. This NASA/ESA Hubble Spare Telescope image provides the sharpest view of NGC 604 so far obtained.
Some 1500 light-years across, this is one of the largest, brightest concentrations of ionised hydrogen (H II) in our local group of galaxies, and is a major centre of star formation.
The gas in NGC 604, around nine tenths of it hydrogen, is gradually collapsing under the force of gravity to create new stars. Once these stars have formed, the vigorous ultraviolet radiation they emit excites the remaining gas in the cloud, making it glow a distinct shade of red. This colour is typical not only of NGC 604 but of other H II regions too.
NGC 604 – click for 1280×919 image
