Even galaxies recycle

On Earth, recycling signs are everywhere, urging us to save our planet while we still can. In space, some galaxies apparently recycle without any signs to remind them.

At least one galaxy isn’t letting materials that could form potential stars go to waste. An international team of scientists led by astronomers Shiwu Zhang and Zheng Cai of Tsinghua University in China has found evidence that an enormous galaxy within an even larger nebula called MAMMOTH-1 is drawing in material from its surroundings to spawn new stars.

However, that material contains elements formed by past supernovae that are thought to have happened within galaxies, with the elements they created being flung into the nebula by the galaxy’s central black hole. This means that the galaxy, which the research team refers to as G-2, is now forming stars from material had previously been hurled out into intergalactic space by a galaxy—either itself or another nearby.