Eventually a galaxy has to grow up and settle down, and stop throwing superheated gas around all over the place. And now astrophysicists have figured out how the glowing "superblobs" around galaxies help to make this happen.

Scientists now believe that the supermassive black holes at the center of young galaxies throw off immense heat as matter falls into them. This heat illuminates the surrounding gas, as seen in the picture above. Interstellar gases, drawn by gravity, cool off and condense, forming new stars. But eventually, the "superblobs" of gas surrounding the galaxy get too hot, and this forces the growth of the galaxy to slow down, scientists say. Here are some stills from a new animation illustrating the process, to go along with a paper in the July 10 issue of The Astrophysical Journal. The stills also have more info in the captions:

[National Geographic]