Is the Milky Way a ‘normal’ galaxy?

Astronomers have already classified millions of galaxies in the Universe. So many that it is not difficult to divide them into different groups according to their shapes or the distribution of matter inside. Spiral, elliptical, barred, lenticular, irregular… The list of new galaxies grows practically every day, and from time to time one appears so different that it deserves to inaugurate a new category. However, studying the shape and structure of the Milky Way, our own galaxy, is an extremely difficult task. We know, for example, that ours is a spiral galaxy, but the fact that we are inside it prevents us from fully observing its characteristics. The problem can be compared to trying to determine what a building looks like without seeing it in its entirety, just by looking out of one of its windows. Despite this, the fact of being ‘inside’ also gives us some advantages. From our position, for example, we can carry out detailed studies of the stellar population of the Milky Way and their chemical compositions. Which gives researchers the tools they need to compare our own galaxy with the many millions of others in the Universe. Related news standard Yes They explain, for the first time, why galaxies have such different shapes José Manuel Nieves The work clarifies, for example, how spiral galaxies ‘drop’ their arms and become lenticular This same week, an international team of researchers from the United States, the United Kingdom and Chile have published an article in ArXiv that does just that: examine a catalog of more than ten thousand galaxies in search of the ones most similar to ours. In this way, the team discovered that, at first glance, there are numerous ‘twins’ of the Milky Way ‘out there’, albeit this is somewhat misleading, since most of them show fundamental differences buried in the data. Looking for other ‘Milky Ways’ In their analysis, the first thing the scientists did was reduce their sample size as much as possible, selecting only those galaxies that matched what we know about the Milky Way into three broad categories. In this way, they were first left with only those with a mass similar to that of the Milky Way. They then discarded all those that showed a different central bulge than our own galaxy, and ultimately only kept those with a similar ‘Hubble type’, a classification system that groups galaxies according to their shapes. At the end of this process, the team was left with 138 galaxies that were, at least superficially, similar to our own. And from there, they delved into the details to see just how close those ‘galactic cousins’ really are to us. Counting stars The researchers plugged the data into a model that predicts star formation, taking into account how stellar winds expel excess gas, which can be drawn toward the center of galaxies. The model also took into account the chemical composition and metallicity of materials within different regions of the galaxies. Which once again reduced the number of galaxies “like ours” from 138 to 56. All of them have in common the fact that they have a long time scale in which they made stars in their outer regions, giving birth to new stars of steady and slow manner. The inner region, on the other hand, in these 56 galaxies experiences a period of intense star formation early in their histories, which is followed by another, much slower stage of star formation in the core, from recycled gas expelled by older stars. in the outer region. These new stars, made from recycled material, have a higher level of metallicity, with heavier elements that were missing from the initial generation of stars. The same pattern that also occurs here, in our own galaxy. This ‘quenching’ of new stars at the galactic centers indicates that these galaxies have already completed most of their stellar production in the past, suggesting that they could be older than the Milky Way. And if this is true, it is possible that by observing them we are seeing the future of the Milky Way itself. Our galaxy, in effect, may one day end up with a dull center as well, and thus these galaxies represent a preview of the next stage of our own evolution. MORE INFORMATION news No There is a second large black hole near Earth news No Hunting for the second closest supermassive black hole to Earth news Yes New data on the mysterious filaments that ‘hang’ from the center of our galaxy «Maybe -they write the authors – these galaxies are the evolutionary successors of the Milky Way, as they are further along in their lives.” Of course, and although there is still much to learn, the study shows that we are not entirely unique. There is a huge variety of galaxy types in the Universe, but at least some of them follow the same rules as our Milky Way, and many are at the same stage in their lives. Studying these similarities can help us learn more about our own home, and also help us figure out what the future holds for us.