Researchers Satoya Nakano and Kengo Tachihara tracked the movement of around 7,000 massive stars within the SMC. These stars, each more than eight times the mass of the Sun, live fast and die young, making them excellent indicators of recent star formation. The scientists observed that the stars exhibited a striking directional split-some moving toward the LMC and others away from it. This pattern hints at intense gravitational interactions.
"When we first got this result, we suspected that there might be an error in our method of analysis," Tachihara said. "However, upon closer examination, the results are indisputable, and we were surprised."
The analysis revealed another unexpected detail: a lack of rotational motion among these massive stars. In typical galaxies, both stars and interstellar gas tend to rotate in unison. But in the SMC, neither the gas nor the stars show signs of rotation. This suggests that the galaxy's internal structure may be fundamentally different from what was previously assumed.
"The stars in the SMC were moving in opposite directions on either side of the galaxy, as though they are being pulled apart," Tachihara explained. "Some of these stars are approaching the LMC, while others are moving away from it, suggesting the gravitational influence of the larger galaxy. This unexpected movement supports the hypothesis that the SMC is being disrupted by the LMC, leading to its gradual destruction."
According to Nakano, the implications of this non-rotating dynamic are significant: "If the SMC is indeed not rotating, previous estimates of its mass and its interaction history with the Milky Way and LMC might need to be revised. This could potentially change our understanding of the history of the three-body interaction between the two Magellanic Clouds and the Milky Way."
Because of its proximity and structural characteristics, the SMC serves as a vital model for exploring the mechanisms of galactic formation in the early universe. With its low metallicity and weak gravitational binding, the SMC resembles the kinds of galaxies that populated the cosmos shortly after the Big Bang. As a result, the team believes these findings may provide critical insights into how galactic mergers and tidal interactions shaped the early universe.
"We are unable to get a 'bird's-eye view' of the galaxy in which we live," noted Tachihara. "As a result, the SMC and the LMC are the only galaxies in which we can observe the details of stellar motion. This research is important because it allows us to study the process of star formation in connection with the motion of stars throughout the galaxy."
Research Report:Evidence of Galactic Interaction in the Small Magellanic Cloud Probed by Gaia-selected Massive Star Candidates
Related Links
Nagoya University in Japan
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