A team of Australian astronomers announces an unexpected discovery in the Large Magellanic Cloud — a neighboring galaxy to the Milky Way. Among the thousands of stars listed, a handful of them are much younger than the others. Something to challenge an already well-established model.
Star clusters are groups of stars bound together by gravity. Traditional models have until now assumed that all the stars in these clusters formed from the same cloud of molecular gas. We then quite naturally thought that these fundamental building blocks of galaxies formed at the same time, giving rise to thousands or millions of stars of the same age and of the same chemical composition. However, an analysis made in the Large Magellanic Cloud which orbits around the Milky Way at approximately 170,000 light years reports a group of about fifteen stars which seem much younger than the others in this same cluster. . This finding challenges the well-established model of how we think these incredibly abundant objects in the universe actually form.
» Our stellar evolution models are based on the assumption that stars in star clusters form from the same material around the same time. says Bi-Qing For, of the International Center for Radio Astronomy Research in Western Australia and lead author of the study. » If this assumption turns out to be incorrect as our results suggest, then our models will need to be reviewed and revised. « .
Of these 15 stellar candidates, seven are located right in the middle. We use the term « stellar candidates » here since a massive cloud obscures astronomers’ vision from Earth, so researchers cannot be certain of their identity at this time. But if this observation is confirmed, it means that scientists will have to find another explanation. However, it would seem that no correlation has been made between interstellar hydrogen and the location of the star clusters studied. Thus the formation of these young stars cannot be fueled by gas from interstellar space. Instead, the researchers believe that these young stars were seeded within their cluster by old stars. If this hypothesis is correct, it means that star clusters could be home to a number of generations of stars that all appeared in the same space.
This isn’t the first time the traditional star formation model has been put to the test. Observations made in 2015 had notably revealed multiple stellar populations with different helium compositions. The next challenge for the team will be to confirm these observations once the cloud of gas and dust has dissipated.