Astronomers have discovered that one of our closest neighboring galaxies is going through a dramatic transformation—and they can watch it happening in real time.
The Small Magellanic Cloud (SMC), a small galaxy visible from the southern hemisphere, has long puzzled scientists because its stars move in an unusual way.
Now, new research suggests the reason is a past collision with its larger neighbor, the Large Magellanic Cloud (LMC).
The SMC and LMC are both satellite galaxies of the Milky Way and have been interacting with each other for hundreds of millions of years.
The SMC is rich in gas and has been studied for decades, with scientists carefully tracking its stars and structure.
However, one mystery remained: unlike most galaxies, the stars in the SMC do not orbit neatly around its center.
In a recent study published in The Astrophysical Journal, researchers from the University of Arizona found that this unusual behavior likely comes from a direct collision between the two galaxies.
According to their findings, the SMC passed through the disk of the LMC a few hundred million years ago, disrupting its entire structure.
Normally, stars in a galaxy follow organized paths, orbiting the center due to gravity. But after this collision, the stars in the SMC were thrown into random, chaotic motion. Instead of moving in smooth orbits, they now move in many different directions, making the galaxy appear disordered.
The collision also affected the gas inside the SMC. Gas is important because it cools and forms stars, and it usually settles into a rotating disk. For years, scientists believed the gas in the SMC was rotating.
However, this new study suggests that this apparent rotation is actually an illusion caused by the galaxy being stretched during the collision. From our point of view, gas moving toward and away from Earth can look like rotation, even when it is not.
The impact of the collision was powerful. As the SMC moved through the LMC, it experienced strong pressure from the larger galaxy’s gas. This pressure likely stripped away or disrupted the SMC’s own gas, further altering its structure.
These findings are important because the SMC has long been used as a model for understanding how galaxies form and evolve. Its simple structure and low levels of heavy elements made it a useful comparison for studying early galaxies in the universe. However, if the SMC has been heavily disturbed by a collision, it may not be as typical as scientists once thought.
The research team used advanced computer simulations to recreate the interaction between the two galaxies and better understand what happened. They also developed new methods to interpret the chaotic motion of stars in galaxies that have experienced collisions.
Interestingly, the collision may also help scientists study dark matter. The impact left a visible mark on the LMC, tilting a central bar-shaped structure. The extent of this tilt could provide clues about how much dark matter the SMC contains.
This discovery shows that galaxies are not static objects but are constantly changing. By observing the SMC and LMC, astronomers are getting a rare, real-time look at how galaxies evolve after dramatic cosmic events.
Source: KSR.
