A new study led by University of Notre Dame researcher Justin Crepp has used the Keck telescope in Hawaii to reveal the picture of a rare brown dwarf - an object too big to be classified as a planet and too small to be called a star - for the first time ever. The team was also able to determine its mass, age and composition, which could help scientists better understand the mysterious substellar objects.
Researchers believe that brown dwarfs are the result of a star that was interrupted during the process of formation. This prevented them from gaining enough mass and pressure to stimulate the process of nuclear fusion, which is the method that the sun uses to release light energy.
Brown dwarfs represent a developmental connection between stars and exoplanets, but they are difficult to study due to the fading of their glow that happens over time due to the lack of the nuclear reactions.
The brown dwarf examined in the current study - HD 4747 B - was the result of 18 years of spectral measurements of a star that pointed to the existence of the substellar object.
"We suspect that these companions form at the same time and from the same material," Crepp said. "As such, you can infer physical properties of the brown dwarf from its parent star, like age and composition. There are no other objects for which we know the mass, age and the metallicity simultaneously and also independent of the light that the companion gives off. We can therefore use HD 4747 B as a test-bed to study brown dwarfs, enabling precision astrophysics studies for a directly imaged substellar object."
Although scientists have typically used theoretical evolutionary models to estimate the mass of brown dwarfs, Crepp and his team used observations of its orbit to build upon these models and acquire a refined mass of HD 4747 B.
The new findings reveal that HD 4747 B has a mass equal to 60 Jupiters, a number that is much lower than current theoretical models predict. Crepp and his team hope that the new measurements will refine current theories and reveal more accurate models that can be used in the estimation of the rare brown dwarf's characteristics.
"This field is transitioning from 'Hey, I found something neat' to 'Hey, I know the mass to within a few percent,'" Crepp said. "Now, we can test theoretical models."
The findings were published on April 1 on the pre-print server arXiv.
