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The line separating the stars from the brown dwarfs may soon be clearer thanks to the new work led by Serge Dieterich of Carnegie. Posted by Astrophysical JournalThe results of his team show that brown dwarfs can be more massive than what astronomers previously thought.
To shine a thousand lights, the stars need the energy resulting from the fusion of the atoms of hydrogen at the bottom of their interiors. If it is too small, the fusion of hydrogen can not occur, so the object cools, darkens and turns into a brown dwarf.
Many researchers are trying to determine the mass, temperature and brightness of objects on both sides of this division.
"Understanding the boundary between stars and brown dwarfs will enhance our understanding of form and evolution, as well as their ability to house habitable planets," said Dieterich.
Dieterich and his colleagues – including Carnegie's Alycia Weinberger, Alan Boss, Jonathan Gagne, Tri Astraatmadja and Maggie Thompson – have shown that brown dwarfs can be more massive than astronomers thought.
The latest theoretical models predict that the limit between stars and brown dwarfs is in objects that are between 70 and 73 times the mass of Jupiter, about 7% of the mass of our Sun, but the results of Dieterich and his team question this prediction.
The Dieterich team has observed two brown dwarfs, called Epsilon Indi B and Epsilon Indi C, which are part of a system that also includes a star of medium brightness – Epsilon Indi A. The two brown dwarfs are much too weak to be stars, but their masses are respectively 75 and 70 times higher than those of Jupiter, according to the researchers' conclusions.
The team performed these measurements using data from two long-term studies – Carnegie astrometric research at the Carnegie Las Campanas observatory and the parallax survey of the Cerro Tololo inter-American observatory conducted by the research consortium neighboring stars – which allowed them to detect the tiny movements of the two brown dwarfs against a background of more distant stars.
To the surprise of the team, their discoveries place Episilon Indi B and C in what was previously considered the star domain, although we know from other observations that they are not stars .
"Taken together, our results mean that existing models need to be revised," concluded Dieterich. "We have shown that the heaviest brown dwarfs and the lightest stars have only slight differences in mass, but despite this, they are destined for different lives: one is stunned and cold, Another shines for billions of years. "
An improved definition of the demarcation line between stars and brown dwarfs could also help astronomers determine how many of them exist in our own galaxy, Weinberger added.
"We are interested in whether stars and brown dwarfs still exist in the same proportion in star-forming regions, which could help us understand the overall livability of our galaxy," she said. .
This work was supported by the Astronomy and Astrophysics Postdoctoral Fellowship Program of the National Science Foundation.
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