# Talk:Brown dwarf

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## Some notes

${\displaystyle 13M_{J}}$ 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.

~${\displaystyle 65M_{J}}$ 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 ${\displaystyle 1R_{J}}$ over the mass range from ${\displaystyle 1M_{J}}$ to ${\displaystyle 75M_{J}}$.

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

Is ${\displaystyle M_{J}}$ really the lower limit where the radius is ${\displaystyle R_{J}}$? 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.

This Bibcode1999RvMA...12..187B might be useful for some more historical information. It summarizes the first three years of brown dwarf research after the discovery of the first brown dwarf. It also includes some information on retractions of discoveries that predate the first. And it explains the Population III mass limit on VLM/BDs (90 Mj) 76.66.203.138 (talk) 14:02, 17 November 2010 (UTC)

Bibcode2000ASPC..212....7L also provides historical context. 76.66.203.138 (talk) 14:17, 17 November 2010 (UTC)

## 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)
An encyclopedia is about that which we do know, rather than that which we don't know.
-Kortoso (talk) 20:59, 16 October 2014 (UTC)

How about mentioning "Temperate Earth-sized planets transiting a nearby ultracool dwarf star" [1] regarding 2MASS J23062928 − 0502285 ? Anonymous, 2 May 2016 (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 from 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

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 I just corrected the mistake. Thanks if you would advice something24.184.234.24 (talk) 17:49, 4 June 2010 (UTC)LeucineZipper

## Coolest

According to the discovery document doi:10.1111/j.1745-3933.2010.00927.x , the coolest is now UGPS 0722-05, and tentatively T10/Y0... 76.66.203.138 (talk) 12:18, 6 November 2010 (UTC)

I agree. The surface temperature of UGPS 0722-05 is 520±40 K, which is right on the borderline between T and Y. It has tentatively been assigned a T10 on the basis of the depths of spectral lines. Whether it is eventually classed as a Y0 will probably depend on the identification of the so-far unidentified spectral feature. This spectral feature is found on Jupiter, but only much more faintly on T9 and T8 stars. PS. I await a more accurate parallax for this star. Mollwollfumble (talk) 09:06, 24 January 2011 (UTC)

## Infrared dwarf

In the first paragraph of section 1: History, I'd like to see the term "infrared dwarf" added to the list of alternative names, so the sentence would read as follows: "Alternative names have been proposed, including planetar, substar, and infrared dwarf."

Presently, "infrared dwarf" redirects to "brown dwarf" in the Wikipedia search box. —Preceding unsigned comment added by Doesper (talkcontribs) 17:04, 6 November 2010 (UTC)

## Article Needs Comparison Pictures

Especially an artists rendition of a brown dwarf next to the Earth. These kinds of pictures are really cool and are found in other Wikipedia astronomy articles. -- Telemachus.forward (talk) 17:16, 5 January 2011 (UTC)

I have added an image to Brown_dwarf#Observational_techniques comparing Jupiter and brown dwarfs Gliese 229B and Teide 1. -- Kheider (talk) 17:38, 5 January 2011 (UTC)

## Tweaks

1. "Y: < 500 K, ultra-cool brown dwarfs (theoretical)" - should "theoretical" annotation be removed since we now have examples?
2. Brown dwarf#Milestones - Adding milestones related to the Y dwarfs seems appropriate.
CoyneT talk 20:01, 30 August 2011 (UTC)
Yes and yes, IMO. :-) --Roentgenium111 (talk) 19:19, 4 September 2011 (UTC)

## field stars?

The article contains the line "multi-color imaging surveys around field stars". is this a typo for "failed stars"? if not, what does "field stars" mean? peace - קיפודנחש (talk) 16:07, 20 December 2011 (UTC)

Field stars are any background stars in the field of view. -- Kheider (talk) 16:13, 20 December 2011 (UTC)
Thanks for the explanation, but it makes the following sentence somewhat murky: "Since those earlier times, numerous searches involving various methods have been conducted to find these objects. Some of those methods included multi-color imaging surveys around field stars". what "background stars" mean, in this context? if one surveys the skies, nothing and everything is "background", no?
to summerize, in light of your explanation what "field stars" mean, I find this sentence unintellegible. peace = קיפודנחש (talk) 19:22, 20 December 2011 (UTC)
Since the statement is unreferenced, I do not know what exact context they meant. But you can compare any giving star to other stars in the same field of view. Which stars are brighter in different filters, etc. Cooler stars will be brighter in the near-IR spectrum and dimmer in the blue. -- Kheider (talk) 20:47, 20 December 2011 (UTC)

## Dumb question.

Could an astronaut walk on a Y-class brown dwarf(since it's only 80 degrees) or would he fall into it?72.82.184.99 (talk) 18:16, 9 July 2012 (UTC)

Allowing for the fact it would have enormous gravity (being a star, after all...), having no solid surface would make it problematic at best. TREKphiler any time you're ready, Uhura 21:07, 9 July 2012 (UTC)

## Discrepency

The first picture/diagram on this page shows Gliese 229, and says it is a brown dwarf. But see the Wikipedia page on Gliese 229, it says it is a red dwarf. One or the other is wrong. Bcwilmot (talk) 02:13, 14 July 2012 (UTC)

Read it again. The star is Gliese 229, the brown dwarf is Gliese 229B, the little dot in the picture. Tbayboy (talk) 04:36, 14 July 2012 (UTC)

## First sentence

The first sentence sounds like not having fusion is characteristic of main sequence starts. It seems ambiguous to me. — Preceding unsigned comment added by 72.209.169.177 (talk) 06:31, 2 November 2012 (UTC)

Good catch. Fixed. TREKphiler any time you're ready, Uhura 18:40, 2 November 2012 (UTC)

## Temperature of Sun-aged brown dwarfs

What would the temperature of a 4–5-Gyr-old brown dwarf be? --JorisvS (talk) 21:47, 2 January 2013 (UTC)

## Abundance

"There are actually fewer brown dwarfs in our cosmic neighborhood than previously thought. Rather than one star for every brown dwarf, there may be as many as six stars for every brown dwarf." Why isn't the fact that we've found far fewer in our cosmic neighborhood (yet) not simply the result of biased detection? --JorisvS (talk) 13:08, 23 January 2013 (UTC)

I believe scientists were expecting WISE to detect many more nearby brown dwarfs than it did. -- Kheider (talk) 14:55, 23 January 2013 (UTC)
Yeah, but in the early days of exoplanet detection all the hot Jupiters detected prompted some to reconsider the theories of planetary formation. People expected to find more than just one hot Jupiter after another and I heard claims back then that these 'were apparently common', even though it was clearly biased detection (and now we unmistakenly know that they are just a minority). Couldn't something similar be going on here? Are brown dwarfs, on average, maybe harder to detect than scientists expected? --JorisvS (talk) 15:36, 23 January 2013 (UTC)
Hot Jupiter's are detected by their gravitational pull on the host star and the further a planet is from the host star the longer the observation arc of the star has to be to detect and confirm the planet. Brown dwarfs are detected by the infrared light they give off. Many brown dwarfs have been detected even 400 ly away. -- Kheider (talk) 16:22, 23 January 2013 (UTC)
Gee, I know that!! I made the comparison to highlight something the psychological side associated with it, not the technical side. The brown dwarfs we have found that far away are young, hot ones... but what about the ones that have substantially cooled? Yes, I know we have found a few of those already, but maybe for some reason we're overlooking many? --JorisvS (talk) 16:42, 23 January 2013 (UTC)
There's a problem with the passage originally quoted at the beginning of this section ("There are actually fewer brown dwarfs in our cosmic neighborhood than previously thought. Rather than one star for every brown dwarf, there may be as many as six stars for every brown dwarf.") The problem: it is outdated, and, in my opinion, should be removed. The source cited is a mid-2012 source. If you look at http://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs, however, you'll find that the third- and fourth-nearest nearest brown dwarfs / stars / systems of such objects, relative to Sol, were discovered in 2013 and 2014, bumping Wolf 359 from 3rd to 5th place. We haven't finished looking, either. These two new nearby discoveries are evidence supporting the hypothesis that brown dwarfs and sub-dwarfs are, in fact, more common than the view expressed in the quoted passage implies. Yes, I know that calling a 2012-source outdated may seem silly in 2014, but work is progressing so rapidly in this part of observational astronomy that it actually does make sense. RobertLovesPi (talk) 16:32, 17 July 2014 (UTC)
If you can find a reliable source that says that, great. The problem is that before the WISE mission astronomers thought there could be a brown dwarf closer than Proxima Centauri but now we know there is nothing closer than Proxima Centauri with a mass greater than 13 Jupiters. And I still question if a rogue object with ~4 Jupiter masses is best called a brown dwarf. -- Kheider (talk) 13:43, 18 July 2014 (UTC)

## Citations etc

A number of sections lack citations totally or have very few for the amount of data covered. I came across this PDF article Observations of Brown Dwarfs by Dr. Gibor Basri, Astronomy Dept. UC Berkley which was published in 2000 that has a lot of very useful info in it. I don't have the time right now to apply it to the article but wanted to let the community know it's out there and might be very useful to the article. Coinmanj (talk) 03:28, 31 January 2013 (UTC)

## Sub-brown dwarfs

The article says that many brown dwarfs at the lower end of the mass range never undergo fusion, linking sub-brown dwarf... but sub-brown dwarf defines these as not brown dwarfs. Are they a subset or a nonoverlapping category? Wnt (talk) 16:13, 14 March 2013 (UTC)

From what I recall, objects between 8 and 13 Jupiter masses are stuck in that grey area between a BIG gas giant planet and a wannabe Brown dwarf. -- Kheider (talk) 17:00, 14 March 2013 (UTC)

## New information has become available

A new paper titled "Statistical Properties of Brown Dwarf Companions: Implica tions for Different Formation Mechanisms" has been submitted, describing the possibilities of brown dwarf formation according to their mass. I wonder if the paper is too new to add anything from it to Wikipedia. --Artman40 (talk) 08:23, 27 March 2013 (UTC)

http://arxiv.org/abs/1303.6442 -- Kheider (talk) 09:30, 27 March 2013 (UTC)
Info from the paper can be added to the article, as long as it is given due weight and presented neutrally, of course. --JorisvS (talk) 22:14, 27 March 2013 (UTC)

## Citation wanted for unclear text

There is some doubt about what is meant by: "Main-sequence stars cool, but eventually reach a minimum luminosity which they can sustain through steady fusion. This varies from star to star, but is generally at least 0.01% the luminosity of our Sun." If this would refer to main sequence stars in general, 0.01% of the luminosity of our Sun would be wrong. So it should refer to K or M class stars in their formation and early stages when they settle down to hydrogen fusion and the core is hotter than the visible surface. If these stars are a group difficult to distinguish from brown dwarfs, this should be made clear by citation and/or rewording the quoted text. Over long enough times, fusion is not steady and stars age. The quoted text was added by Sj at 10:34 hours on the 25th of February 2005. - Fartherred (talk) 17:51, 19 April 2013 (UTC)

Wolf 359, one of the least luminous stars known, apparently has a (bolometric) luminosity of around 0.0001 (i.e. 0.01%) LSun. This means, however, that in the visual part of the spectrum it is far less luminous, because it radiates most of its energy in the infrared. The only ambiguity in the sentence I could find is "luminosity", which I have now changed to "bolometric luminosity". That said, it is a typical statement that has to have a citation. --JorisvS (talk) 18:25, 19 April 2013 (UTC)

## Kulkarni as a citation

I have changed the use of the name Kulkarni as a citation so that it is now in the references list as follows: "While apparently S. Kulkarni does research relating to brown dwarfs at Caltech, placing the name in superscript behind a statement is not the way Wikipedia handles citations. If someone can locate the particular work that supports the statement in the text and fix the citation that would be an improvement. Otherwise this faulty citation will be removed." - Fartherred (talk) 18:29, 19 April 2013 (UTC)

## Planets around Brown Dwarfs

GQ Lup is a star and GQ Lup b a substellar companion orbiting a star, therefore this object does not match the content of this paragraph "Planets around brown dwarfs" and was removed here. Esmera en (talk) 09:48, 30 August 2014 (UTC)

## List of possible planetary-mass brown dwarfs

OTS44 is a 6-17 Jupiter mass object in ChaI (Bonnefoy et al. 2014, A&A 562, A127; Luhman et al. 2004, ApJ, 617, 565) and, therefore, a possible planetary-mass brown dwarf. Esmera en (talk) 09:57, 30 August 2014 (UTC)

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## Who did the Brown Dwarf theoretical prediction?

I see that some people are very uncomfortable with the Brown Dwarf theoretical prediction citation. It will be better if rather than deleting the content they add their claims with citation. — Preceding unsigned comment added by 132.68.75.180 (talk) 12:02, 8 April 2016 (UTC)

The problem was putting it all in the lead, not the substance of the edit. Your most recent edits have placed it in the history section with the existing references to Kumar's work, where it belongs. Tbayboy (talk) 15:26, 8 April 2016 (UTC)
I agree with Tbayboy. The issue isn't whether this material belongs in the article; it's a question of where it should be placed in the article. The history section is the best and most logical destination. Best Regards, Astro4686 (talk) 19:08, 8 April 2016 (UTC)

## Structure

There's no 'structure' section here, and there probably should be. Is their internal structure like Jupiter's, or like the Sun's, etc. Fig (talk) 17:08, 3 September 2016 (UTC)

## "The lightest red dwarfs"

The introduction currently says "Below this range are the sub-brown dwarfs ... and above it are the lightest red dwarfs (M9 V)". This isn't quite correct, since there are a few known L-type main sequence stars, and several M-type brown dwarfs. 203.57.211.237 (talk) 08:42, 22 November 2016 (UTC)