Based on data on the motion of young, massive stars and the structure of interstellar space, astronomers have created a new model of the Small Magellanic Cloud. With his help, they found new evidence that this dwarf galaxy consists of two structures 16 thousand light-years apart.

The Magellanic Clouds are the two largest galaxies that are satellites of the Milky Way. They have been interacting with each other and our Galaxy for at least seven billion years.

Because the Large Cloud is approximately ten times larger than the Small Cloud, it is the cloud most frequently studied when calculating the motion history of these objects. Moreover, it has almost preserved its structure. But tidal forces had a devastating effect on the distribution and speed of stars in the Little Cloud, whose geometry astronomers have been trying to unravel for more than half a century.

To accurately reconstruct and predict the interaction between clouds and the Milky Way, we need to precisely understand the structure of the Little Cloud. Therefore, the authors of the new study collected data from various studies to create a new model of this dwarf galaxy. The preprint of the work is available at. arXiv.

Scientists estimated the speed of stars in different parts of the Small Magellanic Cloud based on data from the Gaia probe. They then examined the structure of gas in interstellar space using the GASKAP radio probe. Combining all this with information from the APOGEE study, the researchers “connected” the stars to their formation sites.

Analyzing the motion and position of these stars, an international group of astronomers concluded that speed is not the only factor that can divide these objects into two groups, as previously assumed. The compositions of stars and interstellar gas also differ in the two groups. The division into structures is most visible in the distribution of cold, dense gas from which stars form.

After comparing all the parameters, scientists concluded that the Small Magellanic Cloud consists of at least two systems. The distance between them is about 16 thousand light-years (about five kiloparsecs). But from Earth’s perspective, they resemble a single galaxy because they completely overlap each other. New stars are born in each of them.

Perhaps both systems are remnants of ancient galaxies. The difference in the metallicity of their stars and the properties of interstellar gas can be explained by different evolutionary histories.

On the other hand, the system closer to us may be the main galaxy, and the distant one may be its “part” of the Great Cloud, formed under the influence of tidal forces. Or there may even be a “bridge” between the Clouds, but this is unlikely because the two structures have almost the same mass.

Low metallicity makes the Small Magellanic Cloud an excellent “laboratory” for studying the physics of interstellar space at redshift z = 2-3 during the “cosmic south”, when the universe is two to three billion years old (an extraordinary coincidence of values) . Therefore, it is important for scientists to understand the structure of this complex object.