New models suggest the Milky Way is not as star-filled as previously thought

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

In their paper published in the journal Astronomy of Nature, the group describes how their model showed that there may not be as many stars in the galaxy as thought.

As the research team notes, our solar system sits on one side of the Milky Way galaxy, well away from the galactic bulge and supermassive black hole believed to be at its center. Such a vantage point, they point out, makes it very difficult to accurately distinguish its structure.

Estimates of its structure are based on estimates made of the number of stars in different parts of the galaxy and then making assumptions based on the structure of other galaxies. For this new study, the research team tried to make such assumptions more accurate by first taking a more precise census of red giants and using that data to build a model to estimate the shape and size of our galaxy.

To perform their census, the team used a variety of techniques to process data from the Apache Point Observatory’s Galactic Evolution Experiment, which allowed them to count red giants that are usually obscured by interstellar dust. This way, they were able to get a more accurate count (closer to 250,000) and also place the red giants more precisely. And this allowed them to get a better picture of their distribution, especially in the bulge around the galactic center.

After adding the data to their model, the research team found that the density of red giants tended to decrease near the midpoint between the edges of the galaxy and the bulge; a finding that differs from previous models, most of which had exponential growth.

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

The team’s work shows that stars in the galaxy are more widespread than previously thought, further suggesting that there may not be as many of them as thought. And if that’s the case, it means the Milky Way galaxy has less mass than previously thought, meaning it could hold more dark matter than previous estimates have indicated.

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