OUR MILKY WAY GALAXY ISN’T VERY WELL MIXED
Our galaxy isn’t as thoroughly mixed as scientists assumed, according to a new study. The new research focuses on the distribution of what astronomers regard as metals, which is really just every element besides hydrogen and helium, even when these elements are gases. Scientists used the Hubble Space Telescope and the Very Large Telescope in Chile to map the metal in dust across the Milky Way in hopes of improving models describing the galaxy’s history.
“Initially, when the Milky Way was formed more than 10 billion years ago, it had no metals,” Annalisa De Cia, an astronomer at the University of Geneva in Switzerland, said. “The stars gradually enriched the environment with the metals they produced.” That enrichment occurs because deep inside a star’s core, atoms smash together to slowly form increasingly heavy types of matter, all the way up through iron. Not all stars explode when they run out of the material that fuels that process, but the stars that do go boom toss all those metals out into their cosmic neighbourhoods where, theoretically, the metals can mix in with the rest of the Milky Way.
Traditionally, scientific models have assumed that the mixing process is pretty effective. However, the new observations, which targeted dust near 25 different stars, suggest that might not be the case, and that instead there are stark local differences in metal levels. As a result, scientists may need to reevaluate their understanding of the Milky Way’s history.