Research reveals tidal forces disrupting nearby dwarf galaxy
by Riko Seibo
Tokyo, Japan (SPX) Apr 14, 2025
New research led by Satoya Nakano and Kengo Tachihara at Nagoya University has uncovered compelling evidence that the Small Magellanic Cloud (SMC), one of the Milky Way’s closest galactic neighbors, is undergoing tidal disruption due to gravitational forces from its larger companion, the Large Magellanic Cloud (LMC). Published in The Astrophysical Journal Supplement Series, the findings offer new perspectives on how galaxies evolve through interactions.
“When we first got this result, we suspected that there might be an error in our method of analysis,” said Tachihara. “However, upon closer examination, the results are indisputable, and we were surprised.”
Using detailed observations of roughly 7,000 massive stars-each more than eight times the Sun’s mass-the team analyzed stellar motions within the SMC. These short-lived stars, found in hydrogen-rich regions, serve as markers of recent star formation and allow astronomers to trace the dynamics of their host galaxy.
According to Tachihara, “The stars in the SMC were moving in opposite directions on either side of the galaxy, as though they are being pulled apart. 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.”
One of the study’s most intriguing results was the lack of observed rotational motion among these massive stars. In contrast to the Milky Way, where young stars typically rotate in step with the interstellar gas from which they formed, SMC stars displayed a starkly different pattern. The absence of rotation among both stars and gas suggests the SMC may not be rotating at all.
Nakano emphasized the implications of this finding: “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 the SMC has properties resembling those of early-universe galaxies-such as low metallicity and weak gravitational cohesion-it offers a valuable analog for studying galactic formation and evolution during the universe’s formative epochs. These insights may shed light on processes that shaped galaxies billions of years ago.
“We are unable to get a ‘bird’s-eye view’ of the galaxy in which we live,” Tachihara noted. “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
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