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Galaxies swell up as they age

24 Apr 2018, 11:38 UTC
Galaxies swell up as they age
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Stars inside young galaxies move in a more orderly fashion around the galaxy’s disc. Image credit: ESA/NASA/Hubble/S. Smartt (Queen’s University Belfast)/R. Gendler
The latest result in galaxy evolution by an international team of researchers shows that as galaxies age, they grow larger and puffier. The team, including researchers from the Australian National University (ANU) and the University of Sydney, studied over 800 galaxies of all kinds in order to deduce the effects of time on a galaxy’s size.
Professor Matthew Colless, director of the ANU Centre of Excellence for All-sky Astrophysics in 3D (ASTRO 3D), says that when a galaxy is young its internal stars orbit along the galactic disc in an orderly fashion. This can be compared to cars going around a race track. “All galaxies look like squashed spheres, but as they grow older they become puffier, with stars going around in all directions,” says Colless. “Our Milky Way is more than 13 billion years old, so it is not young anymore, but the galaxy still has both a central bulge of old stars and spiral arms of young stars.”
In order to determine a galaxy’s shape, the research team recorded the movement of stars using an instrument ...

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