- #1
qraal
- 790
- 3
Hi All
A puzzle of the very distant future. Imagine a brown dwarf, about 0.02 solar masses and 0.1 solar radii. It's moving through the galaxy and has cooled to near ambient so it can accrete mass via its gravity, almost like a giant ramscoop. As it gains mass what does that do to its orbit? It experiences the ISM as a headwind of 15 km/s, thus accreting from about 390 times its frontal area. I'm guessing the brown dwarf would slowly spiral inwards towards the core, unless it is involved in a scattering interaction with another star and is flung out of the galaxy. Alternatively it could collide with another brown dwarf or white dwarf and briefly (on this timescale that is) form a new star. I'm wondering if it might accrete enough mass to eventually ignite as a low mass star by itself or would pycnonuclear reactions transform it into helium before then? Or would it end up in the central black hole? Brown dwarfs close to the ignition mass might do so before the other possibilities claim them. The characteristic time of stellar collisions is ~1022 years and scattering will undo the galaxy in 1019-1020.
A puzzle of the very distant future. Imagine a brown dwarf, about 0.02 solar masses and 0.1 solar radii. It's moving through the galaxy and has cooled to near ambient so it can accrete mass via its gravity, almost like a giant ramscoop. As it gains mass what does that do to its orbit? It experiences the ISM as a headwind of 15 km/s, thus accreting from about 390 times its frontal area. I'm guessing the brown dwarf would slowly spiral inwards towards the core, unless it is involved in a scattering interaction with another star and is flung out of the galaxy. Alternatively it could collide with another brown dwarf or white dwarf and briefly (on this timescale that is) form a new star. I'm wondering if it might accrete enough mass to eventually ignite as a low mass star by itself or would pycnonuclear reactions transform it into helium before then? Or would it end up in the central black hole? Brown dwarfs close to the ignition mass might do so before the other possibilities claim them. The characteristic time of stellar collisions is ~1022 years and scattering will undo the galaxy in 1019-1020.