Most of the Universe’s iron had already been uniformly distributed inside intergalactic gas some 10 billion years ago --- or well before the first galaxy clusters even formed, an international team of astrophysicists report.
Using 26 independent measurements of ten nearby galaxy clusters taken by Japan’s Suzaku x-ray satellite, the team was surprised to find that the gas between these galaxies has iron metallicities about a third of solar. That is, a third of the iron found in our own Sun. (Astronomers term anything heavier than helium, a metal.)
“The fact that the distribution of iron appears so homogeneous indicates that it has been produced by some of the first stars and galaxies that formed after the Big Bang,” Ondrej Urban, the lead author of a paper being published by the Monthly Notices of the Royal Astronomical Society (MNRAS), said in a statement.
The findings are important because iron --- which forms in the last stages of a star that’s about to go supernova --- is crucial to life as we know it. Astrobiologists may in turn push back the clock on when life could have begun based on these findings. That’s because terrestrial mass planets like Earth are laden with iron cores and we ourselves need this stellar by-product to carry oxygen in our bloodstreams.
The paper also notes that the early universe was likely even more violent and topsy-turvy than previously thought.
Iron, and many other elements, was blown out of galaxies by the combined energy of billions of supernovae, as well as outbursts from growing supermassive black holes, the team noted in a statement.
Galaxy clusters, the authors note, have long been valued as unique astrophysical labs which allow cosmologists to study the onset of nucleosynthesis --- the nuclear processes that form elements --- and the chemical enrichment history of the Universe.
It’s been known for some four decades, they note, that a significant portion of the hot plasma in the central regions of galaxy clusters has been enriched by iron produced in stars. Their work corroborates aspects of earlier observations.
What’s unique about these findings however, the authors say, is that the Suzaku measurements found such an unexpectedly homogeneous metal distribution in the outskirts of the nearby Perseus Cluster. Just when and how these metals were injected into the intergalactic medium (the space between galaxies) is not well understood, they note.
Iron’s uniform distribution also means that the combined energy of many supernovae --- as well as the jets and winds of accreting supermassive black holes --- enabled the thorough mixture of the elements across cosmic time, Norbert Werner, the paper’s second author and an astrophysicist at Eötvös Loránd University in Budapest, noted in a statement.