The space between galaxies is not only not as empty as one might think, but it’s actually rich in all the elements that make us and planets.
In a new study, an international team of astronomers showed that oxygen, carbon, and iron are more abundant in the space just around galaxies than in the galaxies themselves. The physicists were able to provide clues on how galaxies and their stars have evolved over cosmic time.
"Previously, we thought that these heavier elements would be recycled into future generations of stars and contribute to building planetary systems," said lead author of the study Benjamin Oppenheimer, from the University of Colorado-Boulder, in a statement. "As it turns out, galaxies aren't very good at recycling.”
The study, published in the Monthly Notices Of The Royal Astronomical Society, combines observations from the Cosmic Origin Spectrograph (COS) in CU-Boulder with 20 computer simulations of large and medium-sized galaxies.
"The remarkable similarity of the galaxies in our simulations to those targeted by the COS team enables us to interpret the observations with greater confidence," said Robert Crain, a Royal Society University Research Fellow at Liverpool John Moores University, and co-author of the study.
The team aimed to simulate different types of galaxies with the goal of explaining why there’s less oxygen around elliptical galaxies compared to spiral ones, and discovered that it’s about the temperature of the circumgalactic medium (CGM). The CGM around ellipticals is much hotter, reaching temperatures of over 1 million kelvin, while it is only less than a third of that in spiral galaxies.
The researchers believe that the enrichment of intergalactic space has been a constant process during the ages of the universe, and as galaxies age, they expel more and more galaxies.
"It takes massive amounts of energy from exploding supernovae and supermassive black holes to launch all these heavy elements into the CGM," said Oppenheimer.
"This is a violent and long-lasting process that can take over 10 billion years, which means that in a galaxy like the Milky Way, this highly ionized oxygen we're observing has been there since before the Sun was born."