Cosmic Crash Turns Nearby Galaxy into Chaos
The Small Magellanic Cloud (SMC) is a neighbor of the Milky Way. Astronomers have studied it for decades. However, its stars do not rotate normally. This mystery finally has an answer.
A Violent Collision
Researchers from the University of Arizona ran computer simulations. They found evidence of a direct crash. Several hundred million years ago, the SMC punched through its larger companion, the Large Magellanic Cloud (LMC). As a result, gravitational forces scrambled the SMC’s stars into chaotic motion.
Gas Stripped Away
The LMC’s gas also pushed against the SMC’s gas. This pressure stripped away the SMC’s rotation. “Imagine water droplets blown off your hand by rushing air,” says graduate student Himansh Rathore. The same thing happened to the SMC.
An Illusion of Rotation
For years, scientists thought the SMC’s gas was rotating. But the collision stretched the galaxy instead. Gas moving toward and away from Earth created a false rotation signal. Therefore, the stars did not inherit orderly motion.
The SMC is small, gas-rich, and low in heavy elements. Astronomers often use it as a model for early universe galaxies. Nevertheless, a galaxy still recovering from a major crash is not normal. “It is not a ‘normal’ galaxy by any means,” says Professor Gurtina Besla.
New Ways to Study Dark Matter
A separate 2025 study found the collision also tilted the LMC’s central bar. The tilt depends on the SMC’s dark matter content. This gives scientists a fresh method to measure dark matter. The crash transformed both galaxies completely.
