The half-light radius of the Milky Way compared to that of the local disc galaxies. credit: Natural astronomy (2024). DOI: 10.1038/s41550-024-02315-7
A small team of astronomers from Yunnan University, the University of Utah, New Mexico State University and St. Andrews University created a new model of the Milky Way galaxy based on the results of their census of red giants.
In their article published in natural astronomy, 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 is located in one arm of the Milky Way galaxy, quite a distance from the galactic bulge and the supermassive black hole believed to be at its center. Such a view, they note, makes it very difficult to accurately discern 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 sought to make such assumptions more accurate by first conducting a more accurate count of red giants and using that data to build a model to estimate the shape and size of our galaxy.
To conduct their count, the team used different techniques to process data from the Apache Point Observatory’s Galactic Evolution Experiment, which allowed them to count red giants that are normally 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 accurately. And this allowed them to better see their distribution, especially in the bulge around the center of the galaxy.
After adding the data to their model, the research team found that the density of red giants tends to level off near the midpoint between the edges of the galaxy and the bulge; a finding that differs from previous models, in most of which they increase exponentially.
This finding, the researchers suggest, indicates that the bulge is not as dense as previously thought. They also found that the half-light radius of the galaxy is roughly twice as large as estimated in previous research efforts.
The team’s work shows that the stars in the galaxy are more spread out than previously thought, further suggesting that there may not be as many of them as thought. And if this is the case, it would mean that the Milky Way galaxy has less mass than previously estimated, which would mean that it may contain more dark matter than previous estimates suggest.
More info:
Jianhui Lian et al, The Broken Exponential Radial Structure and the Larger Size of the Milky Way Galaxy, Natural astronomy (2024). DOI: 10.1038/s41550-024-02315-7
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Quote: New models suggest Milky Way is not as full of stars as previously thought (2024, July 3), retrieved July 4, 2024, from https://phys.org/news/2024-07- milky-stars-previously-thought.html
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