Those other processes include collisions of giant gas clouds within galaxies, internal instabilities, tidal interactions during flybys of smaller galaxies, and minor mergers that don't produce conspicuous distortions. (sciencemag.org)
Hydrogen molecules aren't the best coolant, but they are good enough to enable giant gas clouds, millions of times as massive as the sun, to fall in on themselves. (discovermagazine.com)
The scientists analyzed radio emission from Carbon Monoxide (CO) molecules in giant gas clouds along M51's spiral arms. (public.nrao.edu)