What would be the mass and temperature of a Y9 brown dwarf?
What would be the mass and temperature of a Y9 brown dwarf?
That's a cool question, and I'd like it if there was a nice clear answer. At the moment, as I understand it, the T9-Y0 boundary might be characterized by a change in absorption lines, but it isn't completely clear what that difference is. I don't think anything has been said about something that might be cooler/smaller than a type Y brown dwarf. If so, then there isn't really an answer to your question yet. It may be that the JWST, or other future large-surface-area space-based IR telescopes will be able to detect, identify, and run spectra on cooler objects, and this classification system will start to be more precise at that time. For the moment, there is a paucity of real examples.
Forming opinions as we speak
Is Jupiter a Y brown dwarf?
The coolest known brown dwarf has a temperature of under 300K (around room temperature!) and that's around Y2. Since BDs start off warm and cool slowly over time, I don't think there's going to be many that have reached below 250K by now - even the least massive ones formed very early in the universe's history would be around that temperature after about 12 billion years of cooling. Even if they're that cool, they're still many times more massive than Jupiter though, and so not really a "gas giant" (I'd prefer to call them "hyperjovians" myself, with "superjovian" being sub-browndwarfs from 2-12 jupiter masses).
Yes, but a young, hot superjovian is still not a brown dwarf (heck, even Jupiter itself was pretty warm in its youth), and there's no reason for it to have a spectral type because it's a planet.
AFAIK there isn't a definition for Y9 yet. The Y class is there because there are objects cooler than T, but the "bottom" of it hasn't been observed yet. So your question doesn't really have an answer beyond what I said (probably around 250K, which is what the temperature of the oldest low-mass BDs would be).
Which are only available for hot Jupiters - which are heated by the star and therefore do not have spectral class caused by internal heat.
Long period planets leave no such evidence, for the speed changes of the primary are too slow to observe and would be small even if observed.
Field brown dwarfs do not have any primaries whose spectra to affect.
Huh? While it's true that determining the mass of field brown dwarfs is not possible (or at least, it's very difficult, since brown dwarf models are not very mature) right now, hot Jupiters are not the only planets detectable by the radial velocity method. The best precision HARPS has achieved is about 30 cm/s, enough to detect super-Earths relatively close to the star, and jovians and Neptunes out to much further distances if you observe long enough.
To answer the OP's question, a hypothetical Y9 brown dwarf would probably look a lot like Jupiter does today; my guess is it would have a temperature of about 100-150 K, while the mass could be anywhere between 13 and 80 Jupiter masses. Whether such an object exists out there and is observable is another question. As others have said, the Y9 spectral type hasn't been defined yet.
A double brown dwarf would have stronger spectral and astrometric effects. What is the current observed mass ratio between Epsilon Indi BA/BB?
(Incidentally, if they were "planets" rather than "stars", they would be - what?
And what is the designation scheme for non-planet satellites, when observed?)
Yes, we very much can. We just haven't detected outer system jovians and such via RVs because we haven't been looking long enough, not because we don't have the capability.Originally Posted by chornedsnorkack
According to McCaughrean et al., 2003, it's a T1 and T6 binary with mass 47 and 28 MJ, respectively. These masses were not obtained by RV; rather, they compared them to brown dwarf models, assuming an age of 1.3 Gyr (they note that the uncertainty in the ages dominates the uncertainty in the masses).A double brown dwarf would have stronger spectral and astrometric effects. What is the current observed mass ratio between Epsilon Indi BA/BB?
I'm not sure what you mean here.Incidentally, if they were "planets" rather than "stars", they would be - what?
Non-planet, non-stellar stellar companions are called brown dwarfs if they're massive enough, and named according to the categories of objects we have in our solar system if they're less massive than planets, although we cannot detect such small bodies around other stars at present.
Epsilon Indi have been seen orbiting what, 8...9 years since.
Have the radial velocity and astrometric observations of Epsilon Indi components since given any real mass data to verify those brown dwarf model?
Does the use of minuscle/majuscle in a multiple system component name indicate classifying the component as star or planet? And what is the designation scheme for objects neither stars nor planets when found, e. g. satellites, dwarf planets etc.?
The correct way to designate sub-stellar companions is always a lower-case letter. Planets are named starting with b (since the star is a), and stellar components are named using upper-case letters. For the components of Epsilon Indi B, the correct designations are Epsilon Indi Ba and Bb. Since we have no way to detect dwarf planets or other small objects around other stars at present, that issue hasn't come up and there is no formally accepted way to designate those.
The latest results were published in 2010. No one's bothered to take RVs of it that I can tell, since it's close enough that astrometry will do much better. They indicate that the mass of the system is somewhat larger than previously thought (~120 MJ vs. ~75 MJ). There is not yet enough data to disentangle the individual masses of the two objects; they have not completed an orbit since they were discovered. Their current estimated orbital period is about 16 years.Originally Posted by chornedsnorkack
They don't have the spectra to be late M dwarfs; the 2003 paper classifies them as T1 and T6. Therefore, they're much too cold to be fusing hydrogen in their cores, which is what really defines stars versus sub-stellar objects. The commonly cited 80 MJ limit is probably dependent on composition and other factors, and isn't a hard figure from what I understand.
It appears I may have had some misconceptions myself. See the Wiki article for more. Capital letters are always used for the highest level of hierarchy in a system; close components may then be designated using Aa, Ab, etc.Originally Posted by chornedsnorkack
Ok. I admit I'm not as familiar with orbital dynamics as I should be, but I don't think this is necessary to determine the masses of the two components, which is what we really care about here. If RVs are not needed for that, why waste valuable telescope time taking them?But cannot identify ascending node.
Just because nobody's bothered to publish it doesn't mean the data were not taken; astronomers often get data taken that then sits on the back burner until they have time to look at it, which can take years. That was the latest paper on the subject a quick ADS search turned up; a more careful search might turn up more on it.Latest results? The 2009 paper hoped for a close approach in 2010; obviously it remained unobserved because the 2009 results are the latest as said. In particular, the real astrometric mass ratio remains unknown.