Stars and nebulae

Artist’s impression of a star forming region, a dense interstellar gas and dust cloud where stars are formed in large numbers in intervals of time of the order of a million years. These clouds consist in a mixture of dust, hydrogen, helium and heavy elements previously forged in the interior of previous stars and ejected at the end of their lives in the form of dense winds and supernova explosions. New stars are formed in the cloud from the collapse of dense knots (an example is the star-forming region nebula NGC 346; see figure below). The newly formed stars are very active and characterized by strong variability: bright flares, massive accretion episodes, ejection of plasma in the form of collimated jets, coronal mass ejections, and winds.  Image credit: NASA, ESA and A. Nota (STScI/ESA)