Dozens of runaway stars discovered in the young star cluster R136

A recent study reveals 55 high-velocity stars ejected from the young star cluster R136, located in the Large Magellanic Cloud (a satellite galaxy of the Milky Way), about 160,000 light-years away. This is the first time that such a large number of high-velocity stars have been detected coming from a single cluster.

The discovery increases the number of known runaway stars in this region of the cosmos by up to ten times and is a new scientific contribution from the European Space Agency’s (ESA) Gaia space telescope, which aims to identify the positions, distances and velocities of more than billion stars in our galaxy.

R136 is a star cluster with particular features, containing hundreds of thousands of stars, including the most massive stars known (up to three hundred times the mass of the Sun), and is part of the largest star-forming region of any known so far in the world. a radius of five million light years.

The Gaia mission is ESA’s most ambitious project to detail the stellar mapping of our galaxy. Since its inception, astronomers from the Department of Quantum Physics and Astrophysics of the University of Barcelona (UB), the Institute of Cosmos Sciences of the UB (ICCUB) and the Institute of Space Studies of Catalonia (IEEC) have participated in the Gaia project.

In the new research, led by experts from the University of Amsterdam, the State University of Leiden and the Radboud University of Nijmegen, in the Netherlands, Mark Gieles (ICREA, ICCUB, IEEC) has a prominent participation. Astronomers from the Royal Belgian Observatory (Belgium), Tel-Aviv University (Israel), the Dutch National Institute for Space Research (Netherlands) and the University of Geneva (Switzerland) also sign the work.

R136 and its surroundings, photographed in infrared light. (Photo: NASA, ESA, CSA, STScI, Webb ERO Production Team)

When star clusters form, collisions between smaller star clusters can cause stars to be ejected from the young cluster. The scientific team, led by Mitchel Stoop, a doctoral student at the University of Amsterdam, has discovered that the young cluster R136 has thrown outward up to a third of its most massive stars in the last million years, at speeds exceeding 100,000 km/h. These stars travel up to 1,000 light-years from their birthplace before exploding as supernovae at the end of stellar life and giving rise to a neutron star or black hole.

Another surprising result of the study indicates that there was not a single period in which stars were dynamically ejected, but two. According to Stoop, “the first episode was 1.8 million years ago, when the cluster formed, and fits with the ejection of stars during the formation of the cluster.” «The second episode was only 200,000 years ago and had very different characteristics. For example, the fugitive stars of this second period moved more slowly and did not shoot in random directions as in the first episode, but in a preferred one,” explains the expert.

Gieles, from ICREA, ICCUB and IEEC and co-author of the research, says that “a lot happens in a short time during the formation of massive star clusters and the images only provide a snapshot.” And he adds that “these new observations of the movement of escaping stars are like a ‘rearview mirror’, offering us an unprecedented view of what happened before.”

It should be remembered that the Dutch astronomer Adriaan Blaauw (1914-2010) identified the first signs of the existence of runaway stars, that is, stars that move at high speed through the Milky Way galaxy. With this discovery, Blaauw opened one of the most exciting and surprising chapters of research in astronomy and cosmology that has been revealing its unknowns thanks to a first ESA mission — called Hipparcos — and currently with the Gaia telescope.

The new study is titled “Two waves of massive stars running away from the young cluster R136.” And it has been published in the academic journal Nature. (Source: University of Barcelona)