Can T-tauri stars, due to the fact that they loose matter, become a Brown dwarf?
Not quite-- the start of H-fusion ends the pre-main sequence phase and begins the main sequence phase.Florens said:The fusion already starts in the protostellar phase. First the Deuterium fusion and than in the end of the protostellar phase the H-fusion. Due to the start of H-Fusion the protostar becomes an pre-main sequence star.
The issue of what constitutes mass loss from the T Tauri star is a tricky issue. Once the mass is deep in the potential well of the star, it won't be lost, but there is a lot of gas outside the star that has not officially joined the star yet, and a lot of that can be lost before it ever gets into the star. So what constitutes mass loss from the star itself? A T Tauri star is defined as a star headed to the main sequence, so after all the mass infall and outflow is over, we have to end up with the minimum mass of some 0.1 solar masses. So that's not something that can turn into a brown dwarf without something additional happening, like binary mass transfer. But it's mostly convention-- I think you are more interested in the physics of systems like that, which probably don't much care if the star is going to end up fusing or not.Florens said:And to my question about T-Tauri stars: I have read that Tts can loose about 0,4 sunmasses. So if there is an tts with a mass of f.e 0.47 sunmasses and he looses 0.4 in form of jets and other things; he is under the H-Fusion limit and so an brown dwarf. Could that happen?
That sort of answers the OPs question. But if you allow collapsing gas to a brown dwarf, how do you draw the line between a below-Main Sequence T Tauri and just a plain old blob of gas?Ken G said:A T Tauri star is defined as a star headed to the main sequence
True enough. We have a way of using pretty strange definitions sometimes, like even the definition of a "star" often requires there be nuclear fusion going on-- so "white dwarfs" aren't stars, even when they look like what's in the center of this:Vanadium 50 said:Yeah, but you astromers like that.
When Pluto was deplaneted, the "clear their neighborhood" requirement meant that there were objects that at one time weren't planets because they hadn't cleared their neighborhoods, but at a later time would be, because that process had completed.
In the past when I've looked for the astronomical definition of a "star", it generally mentioned fusion. But I just looked again and I'm not seeing that now (although a top hit says:Vanadium 50 said:If I ran the zoo, I'd de-star them and call them "T Tauri Objects". Yes, that would mean T Tauri, despite the name, is not a star (yet). It can join BL Lacertae and Omega Centauri in that respect.
I don't like that. Black holes are not stars. SMBH's are definitely not stars. I would include white dwarfs, and would like a definition that includes "primarily powered by fusion, including fusion that occurred in the past". That would exclude T Tauri obhects and brown dwarfs (and random gas clouds) and I am OK with that.Ken G said:sufficiently massive
That paper is certainly everything you could want to know about gas giants! It's hard to tell if they have a Hayashi phase (the central part of the blue curves in Figure 7), but the very early parts of the highest-mass gas giants (and middle parts of highest-mass brown dwarfs), have the same slope as the Hayashi-track stars. So probably it's rare for gas giants to be on the Hayashi track, but maybe young high-mass ones. After all, planets are not self-luminous in the optical for very long.Drakkith said: