Galaxies come in a variety of shapes and sizes. Some have buff, spiral arms. Others are necklace-shaped or oblong. They begin their lives rotating in an orderly fashion, but the movement of the stars eventually gets more random and less organized. Astronomers have not been able to pinpoint the reasons behind the changes, but new research poses a somewhat simple explanation–aging. As galaxies age, they tend to be more chaotic. The findings are described in a study published April 3 in Monthly Notices of the Royal Astronomical Society (MNRAS).
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“When we did the analysis, we found that age, consistently, whichever way we slice or dice it, is always the most important parameter,” study co-author and University of Sydney observational astrophysicist Scott Croom said in a statement. “Once you account for age, there is essentially no environmental trend, and it’s similar for mass. If you find a young galaxy it will be rotating, whatever environment it is in, and if you find an old galaxy, it will have more random orbits, whether it’s in a dense environment or a void.”
When galaxies are young, they are star-forming machines. Older ones typically stop forming new stars. Earlier studies suggested that the galaxy’s…
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