🌀 Galactic war in our neighborhood: the Small Magellanic Cloud is being torn apart

The Small Magellanic Cloud, a small dwarf galaxy, is being literally torn apart by its larger neighbor, the Large Magellanic Cloud.

This phenomenon shakes our view of the Milky Way's neighboring galaxies. The stars of the Small Cloud are moving away from their center at a dizzying speed of approximately 37,900 mph (61,000 km/h), and this movement concerns almost the entire galaxy. This discovery, published in the journal Astronomy & Astrophysics, reveals a true gravitational war in our cosmic backyard.


These two galaxies are the closest satellites to our Milky Way. The Large Cloud is located about 160,000 light-years from Earth, while the Small Cloud is a bit farther, at 200,000 light-years. The former contains roughly 30 billion stars, the latter about 3 billion – compared to the Milky Way's 200 billion stars. Both are connected by a vast ribbon of gas and dust, the Magellanic Stream, a remnant of their past interactions with our galaxy.

To reach this discovery, astronomers used over ten years of observations from the VISTA survey of the Magellanic Clouds (VMC). By measuring the movements of thousands of stars, they found that all of them – even those near the center – are moving outward. Their trajectories are aligned along a precise axis, proving that it is the Large Cloud's gravity, not the Milky Way's, that is causing this expansion.

The consequences of this galactic struggle are dramatic. At this rate, the Small Cloud's stars will have traveled several thousand light-years over the next few hundred million years, permanently deforming the galaxy. It is even possible that the Small Cloud will be completely torn in two before both clouds collide with the Milky Way, in about 2.4 billion years. An earlier study had already considered this phenomenon, but the new research shows it affects the whole galaxy.

These results challenge a long-held idea: scientists thought the Small Cloud rotated on itself, like a disk. In reality, its internal movements are dominated by repeated gravitational disturbances from the Large Cloud over billions of years.

Thanks to the exceptional quality of the VMC survey measurements, astronomers hope to soon obtain a more complete picture of the Small Cloud. A new instrument, recently installed on the VISTA telescope, will allow mapping of star movements in three dimensions. That will lift the last unknowns of this small galaxy in turmoil.