New models suggest the Milky Way is not as full of stars as previously thought

A small team of astronomers from the University of Yunnan, the University of Utah, New Mexico State University and the University of St. Andrews has developed a new model of the Milky Way based on the results of their red giant census.

In their article published in the journal Natural astronomy, The group describes how their model showed that there may not be as many stars in the galaxy as previously thought.

As the research team notes, our solar system is located on one arm of the Milky Way, quite a distance from the galaxy’s bulge and the supermassive black hole thought to be at its center. Such a vantage point, they note, makes it very difficult to resolve its structure with precision.

Structure estimates are based on estimating the number of stars in different parts of the galaxy, and then making guesses based on the structure of other galaxies. For this new study, the research team attempted to make such guesses more accurate by first conducting a more precise count of red giants and using that data to build a model to estimate the shape and size of our galaxy.

To perform their count, the team used a variety of techniques to process data from the Apache Point Observatory Galactic Evolution Experiment, allowing them to count the red giants that are normally obscured by interstellar dust. This allowed them to make a more precise count (nearly 250,000) and to place the red giants more precisely. And that allowed them to get a better picture of their distribution, particularly in the bulge around the center of the galaxy.

After feeding the data into their model, the research team found that the density of red giants tended to level off around the midpoint between the galaxy’s edges and the bulge. This finding differs from previous models, most of which reported an exponential increase in density.

This finding, the researchers suggest, shows that the bulge is not as dense as previously thought. They also found that the radius of the galaxy’s half-radius is about twice as large as estimated in previous research efforts.

The team’s work shows that the galaxy’s stars are spread out more widely than previously thought, further suggesting that there may not be as many stars as previously thought. And if that’s the case, that would mean the Milky Way is less massive than previously calculated, which would mean it could contain more dark matter than previous estimates have suggested.

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