Recent analysis of star movements from the European Space Agency’s Gaia spacecraft reveals that the Small Magellanic Cloud (SMC) is being gradually torn apart by gravitational forces from its larger neighbor, the Large Magellanic Cloud (LMC). The SMC, located around 200,000 light-years from Earth, is a dwarf galaxy. As a result, it is gravitationally bound to both the Milky Way and the LMC.
Given that the SMC is only about 7,000 light-years across, it’s a small galaxy by any measure – literally! It’s a member of the Local Group, home to roughly 30 galaxies in our cosmic backyard. This fragile structure has a low metallicity which makes it look like a lot of observed galaxies at the analogous time during the early universe. The SMC is special because it has a weak gravitational potential energy, which makes it quite fragile. It revolves around the LMC approximately every 900 million years and around the Milky Way every 1.5 billion years.
Now the discoveries brought to light by the Gaia spacecraft paint a much bleaker picture of the SMC’s future. Researchers mapped the positions of roughly 2 billion stars within the Milky Way and its surrounding galaxies, leading to new insights into the SMC’s star movements. Unlike the stars in the Milky Way, which rotate around a central axis, stars in the SMC exhibit erratic motion.
“The stars in the SMC were moving in opposite directions on either side of the galaxy, as though they are being pulled apart,” said Kengo Tachihara, a researcher involved in the study.
The findings imply that the gravitational tugs of war from the LMC are best explained by the LMC’s strong influence on the SMC’s large-scale structure. The interstellar gas and dust surrounding the SMC hides its inner workings from us. All of this complexity adds up to not fully understanding the complexity of its stellar dynamics.
“However, upon closer examination, the results are indisputable, and we were surprised,” Tachihara added.
The gravitational interactions between these galaxies might spell a different fate for the SMC than long overdue predictions [7]. Previous models predicted a collision and eventual merger with the Milky Way within a couple of billion years. In a new offending observation, it now seems the SMC could be gradually breaking apart because of these gravitational contests with the LMC.
Further investigations with everimproving data from Gaia are still unlocking the secrets of these nefarious gravitational waltzes. Scientists are continuing to develop their models and further their knowledge about dwarf galaxies. Such work would likely produce exciting results explaining how dwarf galaxies are accreted and digested by larger galaxies.
“We are unable to get a ‘bird’s-eye view’ of the galaxy in which we live – as a result, the SMC and the LMC are the only galaxies in which we can observe the details of stellar motion,” he explained.
The ongoing research using data from Gaia continues to shed light on these complex gravitational interactions. As scientists refine their models and enhance their understanding of these dwarf galaxies, they may uncover even more revelations about how smaller galaxies interact with larger ones.
