The Small Magellanic Cloud, a galaxy close to us, is being torn apart right now, Japanese scientists have discovered

A group of scientists from Nagoya University studied over 7,000 massive stars in the dwarf galaxy Small Magellanic Cloud and came to the conclusion that our distant descendants will not be able to admire this object. This galaxy is literally torn apart by its neighboring, larger galaxy Large Magellanic Cloud.

Vectors show the directions of motion of stars in the Small Magellanic Cloud. Image credit: Nagoya University

Both of these dwarf galaxies, satellites of our Milky Way, serve as a kind of testing ground for studying the evolution of galaxies. They are relatively close: 160 thousand light years to the Large Magellanic Cloud (LMC) and 200 thousand light years to the SMC (Small Magellanic Cloud). The small distance allows us to observe even individual stars in each of them, which provides rich soil for testing cosmological hypotheses. In particular, these galaxies are in many ways reminiscent of the first galaxies in the Universe, and this is the key to understanding the evolution of the universe at its earliest stages, which are currently impossible to look at directly.

The Gaia astrometric space observatory, which has already completed its work, was engaged in mapping stars in the LMC and LMC galaxies. Gaia’s data have not yet been fully processed: two releases are ahead – the fourth in 2026 and the fifth, final, in 2030. Japanese scientists used the third edition of Gaia observations, published in 2022.

«Gaia was able to determine the vector of the star’s motion. Using this information, Japanese researchers created a three-dimensional map of 7,426 stars with a mass greater than eight solar masses in the Small Magellanic Cloud. It turned out that the stars move in different directions, and not synchronously around the center of the galaxy, as would be expected. This allowed us to assume that the neighboring larger galaxy, the Large Magellanic Cloud, is literally tearing its smaller neighbor apart with its gravitational influence. Apparently, over time (although not in the near future), the smaller galaxy will cease to exist as an independent object.

The Small and Large Magellanic Clouds. Image Credit: ESO

What was even more valuable for the work done was that some of the studied stars in the SMO did not rotate at all. This, in turn, did not involve the surrounding gas cloud in motion. Such observed processes contradict established ideas about the evolution of stars and introduce serious errors into calculations – for example, when estimating the mass of galaxies.

The study also provides valuable insights into how galaxies interact and evolve, especially in the early ages of the Universe. The Large Magellanic Cloud, which is similar in structure to primordial galaxies, is key to understanding how star systems form. Observing the motion of stars in the Large and Small Magellanic Clouds helps scientists connect star formation to galaxy dynamics, potentially changing our understanding of the Universe.