Massive brown dwarf detected by astronomers

Massive brown dwarf detected by astronomers
Transit light curve folded to the orbital period of EPIC 212036875 b. The K2 photometric data is indicated with the red points, and the best-fitted transit model with the solid black line. The residuals of the fit are shown in the lower panel. Credit: Persson et al., 2019.

An international team of astronomers has found a new brown dwarf, one of the most massive objects of this type discovered to date. The newly detected brown dwarf, designated EPIC 212036875 b, turns out to be about 50 times more massive than Jupiter. The finding is detailed in a paper published June 13 on arXiv.org.

Brown dwarfs are intermediate objects between planets and stars. Astronomers generally agree that they are substellar objects occupying the mass range between 13 and 80 Jupiter masses. Notably, out of the 2,000 so far detected, only about 400 of them were found to be circling around stars.

Observations have shown that brown dwarfs with masses between 35 and 55 Jupiter masses orbiting their hosts at a relatively close distance (less than 3.0 AU) are extremely rare and difficult to find. This so-called "brown dwarf desert" is constantly studied by astronomers using various techniques, aiming to find other examples of this peculiar type.

Now, an international group of researchers led by Carina M. Persson of Chalmers University of Technology in Sweden reports the finding of a new massive brown dwarf, apparently another representative of this desert. The new , designated EPIC 212036875 b, was identified by NASA's prolonged Kepler mission known as K2, and Persson's team confirmed its brown dwarf nature using ground-based telescopes.

"In this paper, we report the independent discovery and observations of EPIC 212036875 b performed by the KESPRINT consortium," the paper reads as the detection of this object was almost simultaneously reported by other group of astronomers.

According to the study, EPIC 212036875 b is about 51 times as massive as Jupiter, but approximately 17 percent smaller than our solar system's gas giant. These values imply the brown dwarf's mean density at a level of around 108 g/cm3.

Observations conducted by Persson's team found that EPIC 212036875 b orbits its host approximately every 5.17 days at a distance of about 0.06 AU from it. These results confirm that the newfound object represents the brown dwarf desert. Such a close orbit also means that the brown dwarf should be relatively hot—its equilibrium temperature is estimated to be about 1,450 K.

The study reveals that the host, EPIC 212036875, is a slightly evolved star of spectral type F7 V, about 41 percent larger and 15 percent more massive that the sun. Its age was estimated to be around 5.1 billion years and its effective temperature was measured to be 6,230 K.

In concluding remarks, the researchers ponder the possible formation and evolution scenarios for EPIC 212036875 b. They assume that this brown dwarf most likely formed due to gravitational instabilities in a .

"We argue that EPIC 212036875 b formed via gravitational disc instabilities in the outer part of the disc, followed by a quick migration. Orbital tidal circularisation may have started early in its history for a brief period when the brown dwarf's radius was larger," the astronomers concluded.


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More information: Carina M. Persson et al. Greening of the Brown Dwarf Desert. EPIC 212036875 b—a 51 MJ object in a 5 day orbit around an F7 V star. arXiv:1906.05048v2 [astro-ph.EP]. arxiv.org/abs/1906.05048

2019 Science X Network

Citation: Massive brown dwarf detected by astronomers (2019, June 20) retrieved 16 October 2019 from https://phys.org/news/2019-06-massive-brown-dwarf-astronomers.html
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Jun 20, 2019
EPIC 212036875 b is about 51 times as massive as Jupiter, but approximately 17 percent smaller


The surface gravity must be huge, maybe ~170 times Earth normal.

Jun 20, 2019
What is this brown dwarf made of?
A density of 108 grams per cubic centimeter is 4 times the density of gold.
Is there a core of degenerate matter in this star?

Jun 21, 2019
50 times the mass of Jupiter, not enough mass to start fusion. Anton Petrov's simulator says 79 Jupiter masses is required to start fusion.

But a brown dwarf has fusion I assumed.

Jun 22, 2019
50 times the mass of Jupiter, not enough mass to start fusion. Anton Petrov's simulator says 79 Jupiter masses is required to start fusion.

But a brown dwarf has fusion I assumed.


Brown dwarves can fuse deuterium, but that is as far as they get. Once that's gone, it's lights out.

Jun 23, 2019
Initially, I thought this was a limitation on the mass of brown dwarfs. But this one apparently is not the most massive ever detected- instead, it's in a "desert" where no brown dwarfs have been detected until now. That's actually quite important; this will be a paper that gets wide attention and a high citation index, no doubt. Astrophysicists will be citing this paper for a long time to come, and further observations will no doubt further inform this effort to understand these objects that are bigger than planets, but smaller than stars.

Jun 23, 2019
@Castrogiovanni.
Brown dwarves can fuse deuterium, but that is as far as they get. Once that's gone, it's lights out.
As I pointed out long ago, wherever there is hot plasma convection and magnetic field turbulence/swirls, there will also inevitably be 'distributed' PLASMOID events of self-compression/fusion of the Hydrogen entrained in such plasmoids. So 'distributed plasmoid-fusion' heating may continue well beyond initial gravitational-compression-heating and/or Deuterium-fusion heating stages. I even posited that Jupiters 'mysterious heat source/dynamics' even today may be due to such 'distributed' plasmoid-compression/fusion phenomena occurring in and driving much of the observed convection/cyclonic-storms observed even now. That would explain a lot of the heretofore 'Jupiter heating/atmospheric dynamics mysteries' which astronomers/astrophysicists have been wrestling with to date. :)

Jun 24, 2019
Maybe this is why you have no intermediate size black holes

Jun 26, 2019
Brown dwarves can fuse deuterium, but that is as far as they get. Once that's gone, it's lights out.


Brown dwarves at the upper end of the mass scale (above 65 Jupiter masses) can also fuse lithium 7 and hydrogen.

https://en.wikipe...wn_dwarf

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