Many believe that Milky Way is special because it's where the Earth and humans exist. However, from an astronomer's perspective, our galaxy is unusual but not unique, and they have to compare it with other galaxies to determine if it's indeed special.
Is Milky Way Special?
Astronomers have figured out what extraterrestrial scientists could view when they take a distant look at the Milky Way. The new findings imply that, at least in terms of chemistry, our home galaxy is peculiar but not exceptional.
According to study co-lead author Jianhui Lian of the Max Planck Institute for Astronomy in Heidelberg, Germany, scientists have pondered the Milky Way's specialness about other galaxies ever since American astronomer Edwin Hubble discovered that our galaxy is just one among many galaxies about a century ago.
If we want to determine whether the Milky Way is unique, we must find techniques to compare our galaxy with more distant galaxies, Lian said in a statement.
The Milky Way is the galaxy astronomers know the most about because Earth is within it. For instance, the Milky Way is the only spiral galaxy in which astronomers can do extensive individual star analyses to determine their positions, chemical compositions, temperatures, and other characteristics. It is possible to learn more about how our galaxy and other galaxies may have grown and evolved by examining how the concentrations of particular substances have varied over their histories.
But up until now, no one had considered how all these chemical components of the Milky Way would seem from a distance. It is necessary to do so to compare the Milky Way to other galaxies that astronomers have studied from a distance.
Milky Way is Not Common, But Not Unique
The new study relied on developments over the previous ten years to conduct a methodical analysis of the Milky Way. As an illustration, the Gaia mission of the European Space Agency has monitored the brightness, movements, and distances of around 1.5 billion stars in the Milky Way.
It is also simpler to compare the Milky Way to other galaxies because more and better data are available on them. For instance, over 2,700 square degrees of the sky, the MaNGA survey examined approximately 10,000 galaxies in detail. When viewed from Earth, the full moon is visible over an area of around 0.5 square degrees.
The MaNGA survey investigated the chemical evolution of each galaxy from its core to its periphery. Furthermore, thousands of galaxies' histories from the Big Bang to the present can be modeled using contemporary galaxy creation and evolution models. As an illustration, the TNG50 simulation by German and American scientists simulates a cube of space that is more than 230 million light-years large and traces the simultaneous evolution of hundreds of galaxies over 13.8 billion years of cosmic history.
The Milky Way was then compared to 321 galaxies in the MaNGA survey with masses comparable to our galaxy and equal numbers of stars. All these galaxies can also be seen face-on, allowing the researchers to determine how the metal content varies from galaxy to galaxy. The 134 Milky-Way-like galaxies in the TNG50 simulation were found using the same criterion.
Scientists discovered that the Milky Way is neither typical nor exceptional among galaxies. Only 11% of the galaxies in the TNG50 simulation and 1% of the MaNGA sample's galaxies showed a metal distribution pattern resembling the Milky Way. They pointed out that the MaNGA data uncertainties and the TNG50 simulation's constraints on accurate universe modeling may cause the gap between 1 and 11%.
The team also discovered that the Milky Way's irregular form and structure are unusual among galaxies in terms of its chemical makeup.
Study co-lead author Maria Bergemann, an astrophysicist at the Max Planck Institute for Astronomy Bergemann, told Space.com the key implication is that our Milky Way is not typical of other Milky Way-like galaxies. In other words, the Milky Way may have evolved differently compared to other galaxies like it.
The study was published in the journal Nature Astronomy.
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