They are formed by huge clouds of gas that eventually come together in sufficient quantities to kick off nuclear reactions. (blogs.discovermagazine.com)
The winds change speed dramatically, leading to huge cloud formations building up then dying away. (sciencedaily.com)
The eruption shows how blazing energy from the centers of galaxies can heat up huge clouds of gas and prevent new stars from forming quickly, he adds. (sciencemag.org)