A new study from the University of Colorado Boulder reveals that when it comes to basic recycling principles, galaxies are wasteful and selfish.The data, published in Monthly Notices of the Royal Astronomical Society, shows how galaxies eject massive quantities of heavy metals into deep space after the substances are produced during star formation. According to the study, this means that there are higher levels of oxygen, carbon, and iron atoms on the outside of galaxies than there are on the inside.
Researchers had initially assumed the metals, which have greater atomic weight than sodium, would be “recycled into future generations of stars and contribute to building planetary systems,” but it turns out that even cosmic clouds have smokestacks. Though heavy metal discharge isn’t pollution exactly, it’s something damn close, a natural parallel.
Scientists refer to the surrounding reservoir where the expelled gases end up as the circumgalactic medium. This area is many times larger than any galaxy and the study indicates that over half of heavy metals reside in this medium. Not all galaxies are created equal though — the circumgalactic mediums (CGMs) surrounding spiral galaxies were found to contain more oxygen than those of elliptical galaxies. This is because the CGMs of elliptical galaxies are actually much, much hotter than their spiral counterparts, meaning a corresponding reduction in oxygen.