The line that separates stars from brown dwarfs may soon be clearer thanks to new work led by Carnegie's Serge Dieterich. Published by the Astrophysical Journal, his team's findings demonstrate that brown dwarfs can be more massive than astronomers previously thought.

To shine bright, stars need the energy derived from the fusion of hydrogen atoms deep in their interiors. If too small, hydrogen fusion can't occur, so the object cools, darkens, and turns into something called a brown dwarf.

Many researchers are trying to determine the mass, temperature, and brightness of objects on both sides of this divide.

"Understanding the boundary that separates stars from brown dwarfs will improve our understanding of how both form and evolve, as well as whether or not they could possibly host habitable planets," Dieterich explained.

Dieterich and colleagues--including Carnegie's Alycia Weinberger, Alan Boss, Jonathan Gagne, Tri Astraatmadja, and Maggie Thompson--demonstrated that brown dwarfs can be more massive than astronomers thought.

The latest theoretical models predict that the boundary separating stars from brown dwarfs occurs in objects that are between 70 to 73 times the mass of Jupiter, or about 7 percent the mass of our Sun, but the results from Dieterich and team question this prediction.

Dieterich's team observed two brown dwarfs, called Epsilon Indi B and Epsilon Indi C, that are part of a system that also includes a star of medium luminosity--Epsilon Indi A. The two brown dwarfs are much too faint to be stars, but their masses are respectively 75 and 70 times that of Jupiter, according to the researchers' findings.

The team accomplished these measurements using data from two long-term studies--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--which allowed them to detect the minute motions of the two brown dwarfs against the background of more-distant stars.

To the team's surprise, their findings put Episilon Indi B and C in what was previously considered the stellar realm, even though we know from other observations that they are not stars.

"Taken together, our results mean that the existing models need to be revised," Dieterich concluded. "We showed that the heaviest brown dwarfs and the lightest stars may only have slight differences in mass. But despite this, they are destined for different lives--one racing to dim and cool, the other shining for billions of years."

An improved definition of the dividing line between stars and brown dwarfs could also help astronomers determine how many of each exist in our own galaxy, added Weinberger.

"We are interested in whether stars and brown dwarfs always exist in the same proportion to each other in star-forming regions, which could help us understand the overall habitability of our galaxy," she said.

Research paper

Related Links
Carnegie Institution for Science
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth

Tweet

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

SwRI scientists find evidence for early planetary shake-up
San Antonio TX (SPX) Sep 11, 2018
Scientists at Southwest Research Institute studied an unusual pair of asteroids and discovered that their existence points to an early planetary rearrangement in our solar system. These bodies, called Patroclus and Menoetius, are targets of NASA's upcoming Lucy mission. They are around 70 miles wide and orbit around each other as they collectively circle the Sun. They are the only large binary known in the population of ancient bodies referred to as the Trojan asteroids. The two swarms of Trojans ... read more