In recent years, astronomers have been puzzled by formidable mystery. Galaxies don’t appear to have enough raw material within them to form new stars at the rate they do. The Milky Way, for example,  turns about one solar mass’ worth of matter into new stars every year, despite the apparent lack of star forming raw material, such as gas and dust.. Even more perplexing, astronomers believe that galaxies expel gas and dust into outer space due to various processes within the galaxies, such as  supernova explosions of dying stars, as well as the force of radiation from bright stars. This would seem to suggest that galaxies are losing star forming material and should be unable to continue to form new starts at the rate they do.

Recently, Kate Rubin of the Max Planck Institute for Astronomy in Germany, leading a team of astronomers, used the Keck I telescope on Mauna Kea in Hawaii to observe 100 galaxies between 5 and 8 billion light-years away from Earth. They made a startling discovery. For six of the galaxies they observed, gas adrift in space was being recaptured by the galaxies and flowing back into their centers. This confirmed a long held suspicion that the gravitational attraction of galaxies would eventually recycle the gases expelled and use it to form new stars.

However, no such observation was made regarding the other 94 galaxies. Astronomers believe this is because it is difficult to detect the gas flow, which is dependent on the orientation of the galaxy. Essentially, they believe galactic recycling is occurring, but they are unable to confirm it. “This is a key piece of the puzzle and important evidence that cosmic recycling (‘galactic fountains’) could indeed solve the mystery of the missing raw matter,” according to a Max Planck Institute for Astronomy statement.

However, before we breakout the champagne, be aware that galactic recycling may not explain the entire mystery. It’s not clear that galaxies are capturing enough material to account for the amount of formation of new starts. Arguably, the most fundamental law in physics is the conservation of energy This suggests that the material to form new stars is coming from some place. If galactic recycling isn’t the total answer, we must look to other possible sources, perhaps even dark matter.

The universe is still extremely mysterious and our understanding has just scratched the surface. Galactic recycling is likely an important piece of the puzzle regarding new star formation. Like all great mysteries in science, it takes time to get and place all the puzzle pieces before the puzzle picture becomes clear.