Giant Cluster is Spitting Out Massive Stars
By Mark Thompson
Published on: October 16, 2024
We live inside the Milky Way galaxy, which is joined as it drifts through space by two satellite galaxies, the Magellanic Clouds. A star cluster in the Large Magellanic Cloud known as R136 has been the subject of a fascinating discovery. A team of astronomers have discovered 55 high-speed stars that have been ejected from the cluster. The discovery was made using the Gaia satellite, and it seems up to a third of the stars from the cluster have been ejected in the last century.
Understanding R136
R136 is a massive star cluster located in the Tarantula Nebula inside the Large Magellanic Cloud (LMC), which is approximately 160,000 light years from Earth. This cluster is notable for its extraordinary mass and contains some of the most massive stars ever observed. The stars in R136 are relatively young, having formed from the abundant gas in the nebula just a few million years ago.
The Mechanism of Star Ejection
When clusters form, the random movement of gas is transferred to the forming stars. As these stars navigate their clustered environment, interactions with neighboring stars can lead to their ejection from the cluster. This phenomenon was precisely what the astronomers observed using Gaia.
The Gaia Mission
The Gaia space observatory, launched in 2013 by the European Space Agency, has been key in mapping the positions of stars with unprecedented accuracy. Gaia’s data have provided insights not only about the stars themselves but also about their movements and the dynamics of clusters like R136.
High-Speed Ejected Stars
The astronomical team, led by PhD student Mitchel Stoop from the University of Amsterdam, made the groundbreaking discovery of ejected stars traveling at speeds exceeding 100,000 km/hr. This finding underlines the saying, "live fast, die young." Massive stars tend to fuse elements in their cores at an alarming rate, which results in them exhausting their nuclear fuel relatively quickly within a few million years. The ejected stars from R136 typically progress to become supernovae, ultimately resulting in the formation of neutron stars or black holes.
Patterns of ejection
The measurements indicate that the ejections were not limited to a singular event. The first episode occurred approximately 1.8 million years ago, coinciding with the formation of the cluster. A subsequent event took place around 200,000 years ago. Analyzing these two events revealed distinctive characteristics in the directions of the ejected stars. During the initial event, the stars were ejected in random directions, whereas the later event featured ejections predominantly in one direction.
Interaction with Nearby Clusters
According to co-author Alex de Koter, who contributed to the publication of the study in Nature, the directional ejection of stars during the second event suggests interactions with another nearby cluster, which was only identified in 2012. The merging of these two clusters could significantly influence the dynamics and evolutionary paths of the stars involved.
Implications for Galactic Evolution
The revelation that nearly one-third of the stars from R136 have been expelled from their point of origin provides insight into how ejected stars can interact with various regions of the galaxy. These interactions may have contributed to broader cosmic phenomena, including the reionization of the universe, a process during which the universe transitioned from being dominated by ionized gas to a more neutral state, wherein electrons and protons formed neutral hydrogen atoms.
Conclusion
The discovery of the ejected stars from R136 not only expands our understanding of stellar dynamics but also offers a glimpse into the processes shaping the structure of the universe. With further study, researchers hope to unveil additional secrets about the formation and evolution of stars, and how massive clusters like R136 serve as crucial laboratories for stellar evolution.
References
For more information, visit Universe Today.
