Researchers from Carnegie Institution for Science demonstrated that brown dwarfs can be more massive than previously thought
Stars generate energy from the fusion of hydrogen atoms deep in their interiors. When the star is small, hydrogen fusion does not occur and the object cools, darkens, and turns into a brown dwarf. A research led by Serge Dieterich, observational astronomer at the Carnegie Institution for Science demonstrated that brown dwarfs can be more massive than previously thought. The research was published in The Astrophysical Journal on September 18, 2018.
According to the latest theoretical models, the boundary separating stars from brown dwarfs occurs in objects that are between 70 to 73 times the mass of Jupiter, or around 7% the mass of the Sun. The Carnegie research team observed two brown dwarfs including Epsilon Indi B and Epsilon Indi C. The dwarfs belong to a system that also includes Epsilon Indi A, a star of medium luminosity. Although, both the brown dwarfs are very faint to be stars, their masses are respectively 75 and 70 times that of Jupiter. These measurements were acquired using the data from two long-term studies including the Carnegie Astrometric Planet Search at the Carnegie Las Campanas Observatory and the Cerro Tololo Inter-American Observatory Parallax Investigation run by the Research Consortium of Nearby Stars. The data allowed to detect the minute motions of the two brown dwarfs against the background of more-distant stars.
The findings offer a status of star to both Episilon Indi B and C even though other observations suggest that they are not stars. According to the researchers, an improved definition of the dividing line between stars and brown dwarfs is required to determine the number of brown dwarfs and stars in the Milky Way galaxy. The team is further interested to determine whether stars and brown dwarfs always exist in the same proportion to each other to understand the overall habitability of the Milky Way galaxy. The research was supported by the National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship Program.