Where Do All the Stars Come from?... ...New Views of Star Formation with the Spitzer Space Telescope

Abstract

VAST CLOUDS of gas and dust are swirling throughout our Milky Way galaxy. Many of these clouds are stellar nurseries, places where one star (in the case of small clouds) to tens of thousands of stars (in the case of the largest and most massive clouds) are being born right now. These clouds range in size from cores that are 100,000 times the size of the Solar System and a mass of several suns (solar masses), to giant clouds more than ten million times the size of our Solar System and many thousands to tens of thousands of solar masses. A typical star-forming cloud might create very few massive stars (20 solar masses or more), many stars like our Sun, and many more lower-mass stars and brown dwarfs, which are objects with a mass smaller than the 0.08 solar masses needed to produce stars fueled by nuclear fusion. An umbrella term for all of these newly-forming objects is young stellar objects (YSOs).