When is a star not a star? The line that separates stars from brown dwarfs may soon be clearer

September 17, 2018, Carnegie Institution for Science
Artist's conception of the Epsilon Indi system. The two brown dwarfs orbit their common center of mass, which in turn orbits the much more distant primary component, a Sun-like star. By mapping the orbital motion of the brown dwarfs, the team was able to determine their masses. Much like our Solar System's giant planets, brown dwarfs are thought to have cloud belts that encircle the entire object and give it a striped appearance. Credit: Roberto Molar Candanosa and Sergio Dieterich, courtesy of the Carnegie Institution for Science.

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 Gagné, 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 and 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.

Explore further: Milky Way could be home to 100 billion 'failed stars'

More information: Astrophysical Journal (2018). DOI: 10.3847/1538-4357/aadadc

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antialias_physorg
3.9 / 5 (11) Sep 17, 2018
I wonder if there is an intermediate range in which fusion only happens intermittently (i.e. where the pressure from initial fusion reactions is just big enough to drive the mass far enough apart to push it below the fusion limit...until it cools and collapses again to start up fusion once more)
Nik_2213
5 / 5 (3) Sep 17, 2018
DOI link is currently broken, I've reported it.

FWIW, I thought EE B & C were in separate orbits, not a binary pair. Interesting...
jonesdave
2.8 / 5 (9) Sep 17, 2018
DOI link is currently broken, I've reported it.


This would appear to be the Arxiv version:

https://arxiv.org...9880.pdf

It doesn't appear on ApJ using the search function.
Nik_2213
5 / 5 (3) Sep 17, 2018
Thank you.
wduckss
1.7 / 5 (6) Sep 17, 2018
ε Ind Ba/Bb, mass 0,074 MSun, temperature 976 - 1,011 K = brown dwarfs ,

Planets………………Mass Jupiter……..Temperature °K………Distance AU
ROXs 42Bb………….9 ………..………..1,950-2,000°K………..157AU = ?
DH Tauri b………….12…………………2.750…………………..330
CT Chamaeleontis b..10,5-17 ……2.500…………………..440
HD 44627…………..13-14……………1.600-2.400………….275
UScoCTIO 108 b…..14…………………2.600………………….670
Oph 11 B…………...21………………….2.478………………….243
HIP 78530 b………..24…………………2.700………………….740 =?
http://www.svemir...tml#Life
Where the authors have attended school?

Nik_2213
5 / 5 (3) Sep 17, 2018
@WD: Your point ?? New data may trump old, more data may surprise. Enjoy.
rrwillsj
not rated yet Sep 18, 2018
a_p interesting question.

In my opinion, the better our technology, the more sophisticated our methods of analysis? Will continue to expand the categories of possible stars.

Frustrating all the OCD boffins to a frenzy. As all their neat charts and Universal Laws will be constantly challenged by new evidence.

Ain't Science Fun!?!
wduckss
1 / 5 (5) Sep 18, 2018
Nik,
They observe the mass of 0.047 and 0.066 MSun and a temperature of about 1000 ° K.
2-3 x smaller bodies achieve 2-3 x higher temperature.
The old hypothesis and old nonsense. The evidence shows the real state. The mass has little to do with the height of the temperature.

2M1207…….~0,025 M Sun ………2550 ± 150 Temp K
Teide 1………0,052………2600 ± 150
ROXs 42Bb….9 MJ ………...1,950-2,000°K…157AU dist.
HD 106906 b…11………1.800………….~650
DH Tauri b…12…………2.750…………330
CT Chamaeleontis b..10,5-17 …2.500….440

HD 149382.....0,29-0,53...35.500±500
PG0112+104...0,5............30.000
40 Eridani B....0,5............16.500
Lacaillea 9352.0,503.........3.626
L 97-12............0,59 ..........5.700 ±90
valeriy_polulyakh
2 / 5 (4) Sep 18, 2018
Star formation is one of the least comprehended phenomenon in astrophysics. Is there a general theory of star formation? No, there is not. There is a number of models based on computer simulations which include supersonic hydrodynamics with non-ideal MHD turbulence influenced by gravity. They include the line and continuum radiative processes of the energy transfer; a number of chemical processes with dissociation, recombination and ionization, with uncertain nomenclature of atoms and molecules, unknown magnetic fields and formation and destruction of dust particles. In addition there is macrophysics that is an environment in the molecular clouds, clumps and cores; inclusion in the multiple systems, collisions among stellar systems; jets and outflows; radiation pressure. https://www.acade...ormation
https://www.acade...rvations
wduckss
1 / 5 (4) Sep 19, 2018
The formation of a star is not unknowns.
"The mass which creates pressure and the effects of the gravitational forces of Sun are responsible for the melted core. That is the reason why Venus is more warm than Earth and has more active volcanoes, although it is smaller than Earth6. Therefore, there are convincing and verifiable evidence for the objects to shine. They start shining when they reach a sufficient mass if they are in a distant orbit or are independent, or when they reach a sufficient mass and the effects of the gravitational forces if they are closer to the central object (the most often, to a star). .."
https://www.acade...checking
https://www.acade...s_formed
jonesdave
3 / 5 (8) Sep 19, 2018
^^^^^^Either of you two got anything that is actually within the peer reviewed scientific literature? Thought not.
theredpill
3 / 5 (8) Sep 19, 2018
"^^^^^^Either of you two got anything that is actually within the peer reviewed scientific literature? Thought not."

Pretty sure all of the info in Wduckss first 2 posts comes from direct observation and peer reviewed papers about said observations...once again a hostile pointless comment from a hate filled bully. Get on some meds Jones.
jonesdave
3.3 / 5 (7) Sep 19, 2018
"^^^^^^Either of you two got anything that is actually within the peer reviewed scientific literature? Thought not."

Pretty sure all of the info in Wduckss first 2 posts comes from direct observation and peer reviewed papers about said observations...once again a hostile pointless comment from a hate filled bully. Get on some meds Jones.


Sorry? Got anything useful to add? Anything that isn't covered in the paper linked to the article?
wduckss
2.3 / 5 (3) Sep 19, 2018
jd
The article was reviewed, nevertheless is nonsense.
All the evidence provided (of me) has a link.
2M1207 https://en.wikipe...i/2M1207
Teide 1 https://en.wikipe.../Teide_1
DH Tauri b http://www.openex...Tau%20B/ etc
See the miracles, they're all reviewed.
theredpill
3.7 / 5 (6) Sep 19, 2018
"Sorry? Got anything useful to add? Anything that isn't covered in the paper linked to the article?"

No. As usual the title of the article indicates an ongoing confusion you are part of. And as usual when pointed out by a poster you don't like you ignore his observations in favor of an insult. And as usual I shook my head and thought, what the heck happened to this guy to turn him into such a prick....I surmised it was your lack of understanding of charge separation.

jonesdave
3.5 / 5 (8) Sep 19, 2018
I surmised it was your lack of understanding of charge separation.


Lol. What has charge separation got to do with anything?

what the heck happened to this guy to turn him into such a prick.


Being confronted by scientifically illiterate, cultish cranks on practically every science site I go to.

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