The mass of stars in the Milky Way's central bulge (pictured) is about 20 billion times the mass of the Sun — a much higher estimate than in most previous studies.
The central bulge protrudes from the Galaxy's main disk like the yolk of a fried egg and hosts a large density of stars. To estimate the mass of those stars, Elena Valenti at the European Southern Observatory (ESO) in Garching, Germany, and her team used a catalogue of stars of a particular type. The data are from ESO's Visible and Infrared Survey Telescope for Astronomy (VISTA) at the Paranal Observatory in Chile. The team also did a deeper study of all the stars in a small region of the bulge, in part using the Hubble Space Telescope.
Valenti says that this is the first study of the bulge based entirely on observation, without the help of theoretical models.
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Milky Way's bulging waistline. Nature 531, 279 (2016). https://doi.org/10.1038/531279d
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DOI: https://doi.org/10.1038/531279d
