Collision with Large Magellanic Cloud Shatters Orbital Structure of Neighboring Galaxy and Challenges Cosmic Evolution Models

University of Arizona astronomers find the Small Magellanic Cloud was "shattered" by a crash with its neighbor, solving a decades-old mystery of its chaotic stars.

By: AXL Media

Published: Mar 20, 2026, 11:10 AM EDT

Source: Information for this report was sourced from University of Arizona

The Discovery of a Distorted Galactic Neighbor

For decades, the Small Magellanic Cloud (SMC) was considered a pristine example of a dwarf galaxy, yet its internal mechanics have long baffled the scientific community. Unlike typical galaxies where stars follow orderly, circular orbits around a central core, the stars within the SMC move in a chaotic and disorganized fashion. A team from the University of Arizona has now determined that this lack of rotation is the result of a catastrophic "live action" transformation. According to lead author Himansh Rathore, the galaxy was fundamentally altered when it slammed into the Large Magellanic Cloud (LMC), an event that injected massive amounts of energy into the system and shattered its structural integrity.

Atmospheric Pressure and the Stripping of Galactic Gas

The SMC is notably gas-rich, a characteristic that typically leads to the formation of a flat, spinning disk as gravity pulls cooling matter toward the center. However, observations from the Hubble Space Telescope and the Gaia satellite confirmed that the stellar population was not following this expected rotational plane. Researchers explain that as the SMC punched through the dense disk of the LMC a few hundred million years ago, it encountered extreme gravitational and fluid-dynamic pressures. This process effectively blew the rotating gas out of its natural alignment, much like water droplets being stripped from a moving hand by rushing air, leaving the galaxy’s structural components in a state of flux.

Resolving the Optical Illusion of Rotating Gas

One of the most persistent contradictions in Southern Hemisphere astronomy was the observation that the SMC’s gas appeared to rotate while its stars did not. Since stars are born from gas and usually inherit its movement, this discrepancy suggested a fundamental misunderstanding of the galaxy’s physics. The new analysis resolves this mystery by identifying the "rotation" as a sophisticated optical illusion created by the collision. The impact stretched the SMC into an elongated shape; when viewed from Earth, gas moving along this stretched axis created a false signature of rotation that misled astronomers for years regarding the galaxy's true kinetic state.