Astronomii au descoperit că o galaxie învecinată se deplasează în direcții opuse.

Researchers from Nagoya University in Japan have made a significant discovery regarding the motion of Cepheid variable stars in the Small Magellanic Cloud (SMC), our neighboring galaxy. They found that these stars move in opposite directions along two distinct axes. Closer stars are observed moving northeast, while those farther away are shifting southwest. This newly identified motion coexists with a previously observed movement along the northwest-southeast axis, linked to massive stars.

This intricate bidirectional movement indicates that the SMC is being influenced by multiple gravitational forces. The primary influence is from its larger neighbor, the Large Magellanic Cloud (LMC), while a secondary, unidentified mechanism acts in the opposite direction. These findings are detailed in a study published in The Astrophysical Journal Letters.

For the first time, this research examines stellar motions in the SMC by considering the individual distances of stars, rather than assuming a uniform distance of 200,000 light-years from Earth — a simplification that could lead to inaccuracies due to earlier challenges in precise measurement. The researchers utilized data from the Gaia satellite to analyze over 4,200 Cepheid variable stars, which are characterized by their rhythmic pulsation that causes variations in brightness. By comparing the duration of their brightness cycles, astronomers can accurately measure their distances from Earth.

Previous studies indicated that the LMC exerts a stretching force on the SMC. These two galaxies are gravitationally linked and their interactions likely influence each other’s structure and evolution. The new research also considers the gravitational effects from our own Milky Way and the possibility that past close encounters between the two Magellanic Clouds have contributed to the dynamic of the SMC.

The study confirms the theory that the SMC does not rotate, suggesting that its unique irregular shape is affected by gravitational interactions with both the Milky Way and the LMC. According to Dr. Kengo Tachihara from the Department of Physics at Nagoya University, this contradicts previous theories about the structure and dynamics of the galaxy. There is a need to rethink how the SMC, LMC, and Milky Way interact and to develop new simulations that account for the non-rotating nature of the SMC. Satoya Nakano, a doctoral student and lead author of the study, emphasized the importance of this reevaluation for comprehending the complex relationships between these galaxies.

In summary, this research opens new avenues in understanding the dynamics of the Small Magellanic Cloud, urging a re-examination of its interactions with neighboring celestial bodies.