The Large Magellanic Cloud Is Tearing Apart Its Neighboring Galaxy

Astronomers have discovered that the Large Magellanic Cloud (LMC) is gradually pulling apart the Small Magellanic Cloud (SMC) through its gravitational influence.

This visible light mosaic shows the LMC and SMC. Separated by about 21 degrees, the two galaxies are readily visible from the Southern Hemisphere as faint, glowing patches in the night sky.  (Image credit: Axel Mellinger, Central Michigan University/NASA Visualization Studio)

Using 11 years of observations from the VISTA telescope at the European Southern Observatory, researchers found that stars in the Small Magellanic Cloud are not rotating around the galaxy as previously believed. Instead, they are moving outward as a group. Their motions point directly toward the Large Magellanic Cloud, indicating that tidal forces from the larger galaxy are stretching and disrupting its smaller neighbor.

An animation indicating the radial motion of the stars in the SMC. (Image credit: ESO/VISTA VMC/AIP/S. Vijayasree)

The findings suggest that the Small Magellanic Cloud has been significantly distorted over billions of years of interaction. Its irregular shape today is likely the result of this long-term gravitational tug-of-war.

The study also revealed evidence of another mysterious gravitational disturbance that may have occurred around 2 billion years ago. The signatures of this ancient event are still preserved in the motions of some of the galaxy’s oldest stars.

In the distant future, both Magellanic Clouds are expected to continue interacting with the Milky Way and will eventually merge with our galaxy billions of years from now. Until then, the Large Magellanic Cloud will continue to reshape and influence its smaller companion.