An article published in “The Astrophysical Journal Letters” reports the results of a study of the Small Magellanic Cloud that shows how this dwarf galaxy is undergoing distortions in its shape due to various gravitational influences. Satoya Nakano and Kengo Tachihara of Nagoya University, Japan, used data collected by ESA’s Gaia space probe together with information on Cepheid stars collected by the OGLE (Optical Gravitational Lensing Experiment) project. This allowed them to determine the distances of 4,236 Cepheids and the anomalies in their motions. The conclusion is that the Small Magellanic Cloud is undergoing a gravitational influence from the Large Magellanic Cloud and another as yet unknown source.
The Small Magellanic Cloud is one of the dwarf galaxies satellite of the Milky Way. Due to its relative proximity, it’s the subject of various studies by astronomers. They include the interactions between the Milky Way and its satellites, but these are complex studies because they require precise measurements of the movements of stars within the various dwarf galaxies and the Milky Way.
The Gaia space probe, whose mission ended recently, is providing considerable help because for years, it has detected with great precision the position of a huge quantity of stars by following their movements over time. The data collected and published on various occasions is very useful in various astronomical research, in this case, regarding the motions of stars in the Small Magellanic Cloud.
Among the stars examined by the Gaia space probe, there are the Cepheids, variable stars that are used by astronomers to measure cosmic distances. That’s thanks to the fact that they show regular pulsations that make them “standard candles” in the measurement of their distances. The OGLE project, which deals among other things, with the classification of variable stars, has also collected a lot of information on Cepheids.
Combining data from the Gaia mission’s Data Release 3 (DR3) and the OGLE project’s OGLE-IV phase, researchers Satoya Nakano and Kengo Tachihara mapped the motions of 4,236 Cepheids in the Small Magellanic Cloud. The result indicates that this dwarf galaxy is subject to various gravitational influences that pull the stars closest to Earth towards the northeast and the more distant ones in the opposite direction.
It’s certainly not surprising that the Large Magellanic Cloud exerts an influence on its neighbor, and the two researchers, together with their colleague Mao Tamashiro, had already reported evidence in an article published in “The Astrophysical Journal Supplement Series” published last April. However, another gravitational source hasn’t been identified yet. It could be the Milky Way or the long-term effects of a close encounter between the two Magellanic Clouds that occurred in the distant past.
These interactions may also have caused the Small Magellanic Cloud’s stars not to rotate coherently around its nucleus. Over time, there may have been various interactions with its neighbors that have caused dynamical anomalies within it.
This study challenges previous theories about the structure and dynamics of the Small Magellanic Cloud. This means that its interactions with the Large Magellanic Cloud and the Milky Way, and perhaps with other dwarf galaxies, need to be rethought. For this reason, the two Japanese researchers concluded that computer simulations are needed to reproduce the findings derived from these observations.
The evolution of the Small Magellanic Cloud may seem like a scientific curiosity, but interactions between galaxies are a crucial factor in their evolution, so studies like this are followed with interest by astronomers.
