What do you mean by this? Storing implies retrieval. How's that ever going to happen?stefan r said:storing hydrogen for future galactic development
|Glitch| said:Is this not something we already knew? Brown dwarfs are objects that fuse deuterium and/or lithium and range anywhere from 13 to 80 Jupiter masses. This 6.7% of the Sun's mass is just another way of saying 70.2 Jupiter masses. Which is slightly less massive than originally estimated.
And now with a more precise estimate. That is the point.|Glitch| said:Which is slightly less massive than originally estimated.
That is true. It is only estimated that somewhere between 13 and 14 Jupiter masses deuterium begins to fuse, and Brown Dwarf is only able to fuse lithium once it became greater than 65 Jupiter masses. The upper end for a Brown dwarf was estimated to be between 75 and 80 Jupiter masses before hydrogen fusion began. According to the article, these new observations suggest hydrogen fusion can began with only 70.2 Jupiter masses (6.7% of the sun's mass).nikkkom said:I take it the exact boundary was not something we already knew.
Bandersnatch said:What do you mean by this? Storing implies retrieval. How's that ever going to happen?
stefan r said:I do not need to know. If no one can retrieve the hydrogen then the brown dwarf succeed in avoiding retrieval too. I just wanted to know why it is labeled "failed star". Why is proton fusion considered a success?
will depend on elements it is made of and the temperature.snorkack said:What is the central density of a 70 Jupiter mass brown dwarf?
stefan r said:will depend on elements it is made of and the temperature.
snorkack said:Is it a property of brown dwarfs, shared with planets and white dwarfs, that their interior is degenerate and its density depends weakly on temperature?
How so?stefan r said:Yes. but gas law is still there adding pressure. Someone should calculate for pure hydrogen.
When stars collapse from gas clouds they are hot enough to stop contracting for awhile. Should be true for brown dwarfs and planets too. The gas law still applies in degenerate matter but it is tiny.
snorkack said:How so?
Heat compressed ice. At warming to about 0 degrees, the pressure drops to 6 mbar for a wide range of initial pressures of compressed ice.
While most other condensed substances do increase pressure on heating, it is not clear that the pressure should be a linear sum of ideal gas pressure to the condensed matter pressure.
snorkack said:Do brown dwarfs contain any oxygen nuclei?
mfb said:Everything apart from the very first stars does. Why do you ask?
mfb said:Everything apart from the very first stars does. Why do you ask?
snorkack said:Do ice, rock and iron in brown dwarfs remain evenly dissolved in hydrogen and helium, or precipitate into the centre?
When powerful shock waves are emitted from atmosphere of a gas giant, such as by explosions of comet fragments, precisely how do the sound waves propagate through gas giant core to the far side? Are they only refracted by smooth and continuous profile of sound speed in hot compressed hydrogen, or do they encounter any composition discontinuities?stefan r said:Jupiter is still an open research field. We certainly have no samples from inside of a gas giant. The Juno spacecraft is supposed to collect some data to help determine if there is a rocky core. "Rocky" is not very detailed.
snorkack said:What is the central density of a 70 Jupiter mass brown dwarf?
qraal said:Very high? They can be modeled as n=1.5 Polytropes, which means their central density is ~6 times their average density. In solar units a brown dwarf's radius is roughly its mass i.e. a 0.07 Solar mass brown dwarf would have a radius of ~0.07 solar radii. So it'd roughly have a central density of 6 x (0.07/(0.07)^3) x average solar density ~1,730 g/cc. The Sun only manages 150 g/cc, so it's pretty dense.
A useful review can be found here: https://www.hindawi.com/journals/aa/2016/5743272/
0.64–1.13RJ with an average radius of 0.83RJ.
A brown dwarf is a type of celestial object that is often described as a "failed star." It is larger than a planet, but not large enough to sustain nuclear fusion in its core like a star does. Instead, it primarily emits heat and light from residual heat leftover from its formation.
The first direct measurement of the brown dwarf mass limit was achieved through observations using the Very Large Telescope (VLT) in Chile. The VLT is equipped with a high-precision instrument called the Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) instrument, which was used to directly measure the mass of a brown dwarf orbiting a nearby star.
This measurement is significant because it provides a more accurate understanding of the lower limit of brown dwarf masses. Previously, this limit was only estimated through theoretical models. Now, with a direct measurement, scientists can better understand the formation and evolution of these objects and their place in the universe.
The first direct measurement of the brown dwarf mass limit was found to be 6.7% of the mass of the Sun. This means that any object with a mass below 6.7% of the Sun's mass cannot sustain nuclear fusion and is therefore considered a brown dwarf.
This measurement has implications for our understanding of other objects in the universe, such as exoplanets, brown dwarfs, and even stars. It allows scientists to better classify and distinguish between different types of objects, leading to a deeper understanding of the formation and evolution of our universe.