Exploring the cosmic uniqueness: How would aliens perceive our Milky Way?

Researchers from the German Max Planck Institute for Astronomy conducted a study aimed at enhancing our understanding of space. They attempt to identify the result that could be obtained by alien astronomers who conduct a thorough examination of the Milky Way, akin to our investigations of various galaxies observable in our sky.

Thanks to this experiment, we now have the ability to accurately compare how our home galaxy differs from other galaxies, specifically those distant galaxies we can observe. This provides an answer to the age-old question: Is the Milky Way unique on a cosmic scale? If we trust the comparisons made by astronomers, we can conclude that while it is indeed remarkable, it isn't absolutely unique.

By observing other galaxies, we can determine their shape and spectrographic spectrum, essentially their color. These observations provide information about the galaxy's chemical composition and characteristics. If an alien astronaut conducted a similar investigation of the Milky Way, they would find that most of the stars are composed primarily of hydrogen and helium, with a small proportion of heavier elements. Some of these heavy particles (which astronomers refer to as "metals", though they are not chemically metal), are dispersed into space via supernova explosions, while others are ejected from still living stars through solar wind.

Alien astronomers would likely note the increasing amount of gas in interstellar space. By tracking the distribution of these dust clouds, they could determine the areas of the galaxy that contain older stars as opposed to newer ones. They would also realize that the metal content in stars increases with the distance from the core of the galaxy.

The results of the simulation were compared to properties of other galaxies. Researchers considered 321 galaxies of similar mass to the Milky Way that also produce a comparable number of stars. These galaxies were chosen specifically based on their visibility from above, which aids in measuring their diameter. Additionally, they studied 134 galaxies similar to the Milky Way found in the simulated TNG50 universe.

The scholars concluded from the study that while the Milky Way is noteworthy for its abundance and distribution of metals on a cosmic scale, it is not unique. Approximately 11 percent of galaxies in the TNG50 simulation and 1 percent of those we observe showed similar properties to ours. Scientists propose that the distinguishing trait of galaxies like ours is the low metallic content in stars located in the center of the galaxy. This may be a result of them being encased in a so-called bulge, a spherical area populated by older stars that surround the core of the galaxy.