Talk:Brown dwarf

Some notes

$13M_{J}$ is the critical threshold for Deuterium fusion; as a result, some descriptions implicitly put the lower bound on mass there. However, most actualy definitions of brown dwarfs clarify their existence independently of mass, and wonder openly about what the lower bound will turn out to be.

~$65M_{J}$ is the critical threshold for burning off Lithium, so the heavier brown dwarfs (which will also be warmer and easier to spot, and make up many of the observed dwarfs) may deplete their lithium . I'm not sure if it is possible for a brown dwarf to stay hot for long enough to deplete all of its lithium... many things [including the threshold mass for helium fusion] depend on the initial composition of the dwarf.

The radius of a brown dwarf is around $1R_{J}$ over the mass range from $1M_{J}$ to $75M_{J}$.

+sj + 10:43, 25 Feb 2005 (UTC)

Is $M_{J}$ really the lower limit where the radius is $R_{J}$? Given that the radius would be roughly constant over two orders of magnitude, it seems like quite a coincidence that our very own Jupiter would define the lower limit of that range. --Doradus 18:36, Feb 25, 2005 (UTC)

One of the interesting things about brown dwarfs is that they would carry large storehouses of energy to the distant future of the universe. All the other stars will have used up the available interstellar hydrogen and died off. Brown dwarf stars in binary pairs will eventually coalesce by gravitational radiation and tidal losses. The two stars although individually too small to burn hydrogen when combined might form new red dwarfs. Trillions of years in the future they might be the only active stars left. 70.108.138.233 02:00, 21 October 2005 (UTC) [marko]

I don't think the explanation of why brown dwarfs are all roughly the same size is clear. The article says that among the less massive brown dwarfs, Coulomb pressure dominates; among the more massive, EDP dominates. Is this saying that, contrary to the expectation that a more massive brown dwarf would actually be smaller as a result of greater pressure, under higher pressure EDP takes over and therefore size is roughly constant? Incidentally, can we get some physicist to write an article on Coulomb pressure? The link to Coulomb pressure obviously leads.. nowhere.

Life in planets around brown dwarfs

I don't suppose someone more experienced than I could comment on this and maybe add something to the article?

The observations also imply that brown dwarfs might be good targets for future planet-hunting missions. Astronomers do not know if life could exist on planets around brown dwarfs.

This was from spaceref.com today. I was under the impression that only stars of our size were good for that. Do any brown dwarfs last long enough for life to theoretically develop? How close would a planet have to be to be in the habitable zone, the one that goes from a little ways inside our orbit to about 2 AU if I remember correctly? Also what would it look like? Even though I'm interested in the technical details as well it would be interesting if some articles could have an actual depiction on what it would look like to be on a planet orbiting a star. I asked on the Alpha Centauri page as well what it would look like and just remembered that I should go check that to see if I got a response. Mithridates 08:24, 21 October 2005 (UTC)

Wouldn't a solar system with a brown dwarf be too cold to have life? Hardee67 02:21, 25 July 2006 (UTC)

Life as we know it, certainly, but I think Alan Dean Foster might have something to say about it. TREKphiler ^{hit me ♠} 14:07, 16 November 2008 (UTC)

Cha 110913-773444 in Ido

Hi,

There's an article on Cha 110913-773444 on the Ido Wikipedia so please add it to the interwiki links if a page on it gets created over here. Mithridates 19:13, 30 November 2005 (UTC)

Cha 110913-773444 and its discoverers

"Astronomers from Pennsylvania State University have detected what they believe to be a disk of gas and dust similar to the one hypothized to have formed our own solar system. Cha 110913-773444 is the smallest brown dwarf..."

Actually, only the team leader (Kevin Luhman) is an astronomer fron Penn State. The others are from the Autonomous University of Mexico, from the University of Michigan, and from the CFA at Harvard.

Tables at the end of the article

The tables at the end of the article ought to be removed from the article. Most "brown dwarfs" are simply candidates for being brown dwarfs so it would be extremely difficult to state for example which brown dwarf is the most massive or youngest. At young ages brown dwarfs and low mass stars are completely indistinguishable. Massive brown dwarfs and low mass stars are virtually indistinguishable since both deplete their stores of lithium in a short period of time. These and many others facts are true for most of those categories.

I have added a split section request - they should be in a list of brown dwarfs article instead. 132.205.44.5 22:41, 18 July 2007 (UTC)

Considered Stars or Not?

Hoping to clarify whether most astronomers consider brown dwarfs to be stars or not, and the article didn't offer a concrete answer for me (the first line includes "sub-stellar objects", which is particularly confusing). I understand this may be because there isn't yet any scientific consensus. Specifically I would like to clarify in interstellar planet and Planemo whether 2M1207b, Oph_162225-240515, and/or Cha_110913-773444 can be considered examples of such objects. Specifically, the Oph_162225-240515 article seems the exception in that one of "a pair of planetary mass objects or "planemos" that have been reported as orbiting each other, and not any star..." is later referred to as a "brown dwarf". Most of the other articles seem to refer to brown dwarfs as stars.

Since I'm interested in extrasolar planets, it would be interesting to me if one had been discovered. Any input? Kiaparowits 18:55, 27 August 2006 (UTC)

Would the "internal level of activity" dividing a brown dwarf from a gas giant) depend upon the (stellar or planetary) bodies with which it is associated? The answer to Kiaparowits' question might well be "boundary depends on circumstances."

Note - Y-dwarf

Just adding a note for Y-dwarf to be added on this page. Thanks, CarpD, 6/27/07.

CFBDS0059 and Y class dwarf both redirect here for now. Both articles should be expanded as material becomes available. davidwr/(talk)/(contribs)/(e-mail) 21:26, 14 April 2008 (UTC)

I'll make my own note on Y class dwarf as an article needed. If none else is faster, that is... Said: Rursus (☻) 13:10, 16 November 2008 (UTC)

I have added the info about 2 newly discovered brown subdwarves (UGPS 0722-05 and SDWFS 1433+35) proposed as prototypes of the spectral class Y0. --Yigor (talk) 10:22, 22 April 2010 (UTC)

Visible light?

Brown dwarfs, a term coined by Jill Tarter in 1975, were originally called black dwarfs, a classification for dark substellar objects floating freely in space which were too low in mass to sustain stable hydrogen fusion (the term black dwarf currently refers to a white dwarf that has cooled down so that it no longer emits heat or light).

A star that doesn't emit heat? Surely it can emit light of invisible wavelengths and surely must emit some form of heat? ArdClose (talk) 14:13, 19 December 2007 (UTC)

It emits cold! In the form of IR-suckup-radiation!! Said: Rursus (☻) 13:23, 16 November 2008 (UTC)

Or, jokes aside: it emits heat, but it doesn't produce any by proton-hydrogen fusion. Only by deuterium fusion, or simply by old contraction heat. Said: Rursus (☻) 13:25, 16 November 2008 (UTC)

Oh, forget it: I misread. The black dwarves would emit virtually no heat, but black dwarves don't exist, they are believed to come to existence in a later age of the Universe. Said: Rursus (☻) 13:29, 16 November 2008 (UTC)

Area 403

This is coming back with a 403 warning... TREKphiler ^{hit me ♠} 06:45, 8 September 2008 (UTC)

LOL at ABC

ABC came out with a miniseries a while ago called "Impact", and it is pretty stupid because it misstates the properties of a brown dwarf. Perhaps what they should've said was black dwarf, a type of star which is not believed to exist yet, but labeling it a "brown dwarf" only serves to confuse people. That being said, what would actually happen if a hyperdense chunk of matter were to make the mass of the moon double that of the Earth? — Rickyrab | Talk 03:42, 9 October 2009 (UTC)

Gigayear

The link for a gigayear directs to year and not gigayear? Is there a reason for this? —Preceding unsigned comment added by 98.236.186.149 (talk) 16:25, 8 April 2010 (UTC)

Mistake

I mistakenly put the spectral class of a brown dwarf (T9/Y0) in the wrong column. I tried to correct the mistake, but got an edit conflict instead. How do I effect a correction? 24.184.234.24 (talk) 17:46, 4 June 2010 (UTC)LeucineZipper