Michigan University astronomers confirmed a recent collision (be careful: ‘recent’ in this context means ‘a few million years ago’) of two satellite galaxies in the Milky Way. These are the Small Magellanic Cloud (SMC) and the Large Magellanic Cloud (LMC). With the help of a new, powerful space telescope, they found that the southeast region (called ‘the Wing’) of Small Magellanic Cloud is moving away from its main body, making it clear that the satellite galaxies had recently collided. Sally Oey, professor of astronomy at Michigan said that the Wing is its own separate region that is moving away from the rest of the Cloud. The findings are published in The Astrophysical Journal Letters dated November 1, 2018.
Oey and fellow researcher Johnny Dorigo Jones were observing the SMC for ‘runaway stars’ using date release from Gaia, the European Space Agency’s new orbiting telescope. Gaia is designed to scan stars repeatedly over the years to map their motion in real time so that their movements can be measured. Removing the bulk motion of SMC, the team focused on the velocity of individual stars in order to study the physical processes within the cloud. While doing this, they noted that all the stars within the Wing of SMC are moving in the same direction, with similar speed. And this made them conclude that the SMC and the LMC possibly had a collision a few million years ago.
Gurtina Besla of the University of Arizona, who contributed to the study, had predicted along with her team a few years back that a collision would force the wing region to move toward the LMC. Instead, if the galaxies passed near each other without collision, the stars in the Wing region would be moving along with the rest of SMC. As the wing is moving away from it, it is clear that a direct collision has occurred. So, what Oey and team observed offers conclusive proof to Besla’s hypothesis. There indeed was a collision between the galaxies LMC and SMC.