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It seems to me that if we have not observed any red dwarf stars with zero metal content, then we have indeed observed red dwarf stars that have moved off the main sequence and we are still left with the puzzle of determining the precise age of the universe. About all we can say for certain is that the universe should be much older than the estimates that are popular at the moment.
The reason I bring this up is because I cannot imagine how you find a red dwarf that has gone cold. It seems unlikely that they would become white dwarfs harboring degenerate matter. This is a case of an absence of something indicating a condition we have failed to properly conisider.
I disagree with this statement:
Red dwarfs never initiate helium fusion and so cannot become red giants |
Red giants, at least as expected with Sun-like stars, occur before the initiation of helium fusion, with shell hydrogen fusion. Although it might take more-then-the-current-age-of-the-Universe for red dwarfs to reach the point of having an inert helium core, I could imagine this state of affairs, at least with the bigger end of red dwarfs. Does anyone have any better information? Joffan 19:02, 16 September 2005 (UTC)
At the begining of the Main Sequence red dwarfs are fully convective. As a red dwarf ages the hydrogen to helium ratio decreases throughout the star. This forces the temperature of the core up to maintain the rate of fusion. At some point this causes a radiative shell to develop between a convective core and a convective exterior. The hydrogen outside the core is no longer available for fusion and the evolution proceeds rapidly. What happens next depends upon mass.
Disclaimer, much of what I have said above occurs on timescales greater than the age of the Universe, so is completely untestable. Thus this is more speculation than rigorous science. -- Ealdian 14:26, 17 August 2006 (UTC)
Actually, if a red dwarf has a mass greater than 0.4 mass of the Sun, not all of the star’s region is convection zone and it could become a red giant. —- Anonymous 17:38, 29 June 2019 — Preceding unsigned comment added by 2402:800:61B1:773A:1464:BA3B:13D2:A65D ( talk)
Stars of extremely high mass that burned out quickly, by cosmological standards, and thereby created all the metals needed for the current crop of Population II and Population I stars. Shouldn't this have left us with a very high number of neutron stars, magnetars, and black holes? Wouldn't the consequences of having a large number of such objects around be rather serious?
Here, I am not criticizing Wikipedia as this seems to be an accurate exposition of current theory. Nevertheless, I do have serious misgivings about the theory. Granted, Astronomers, Astrophysicists, and Comologists need a theory to work with and from, but they seem terribly cocksure at times.
Quoting the article on Pop III stars here, because I cannot get the talk tab to work on that article:
"If these stars were able to form properly, their lifespan would be extremely short, certainly less than one million years. As they can no longer form today, viewing one would require us to look to the very edges of the observable universe. (Since the time it takes light to reach Earth from great distances is extremely long, it is possile to see "back in time" by looking farther away.) Seeing this distance while still being able to resolve a star could prove difficult even for the James Webb Space Telescope."
If the theory concerning these putative stars is in any way correct, then JWST should be able to view entire galaxies of such stars, yes? The spectra of nearly all the stars should all be very nearly the same, depending upon the age of the putative galaxies of Pop III stars. In fact I would expect the spectra of such young galaxies to fall into "bins" according to their ages. A galaxy only one million years old should be easily distinguishable from one that is slightly older than one million years and so on until all the Pop III stars have had time to burn out. Metalicity galaxy wide should increase with age in almost stair-step fashion.
It amazes me, by the way, that something around one percent or less of elements heavier than helium can have such profound effects on stellar size. Current counts suggest that the overwhelming majority of Pop II and Pop I stars are K to M class dwarfs. Why the anticipated paucity of such stars in Pop III? Simply because we have not found any such stars that have turned off the main sequence?
Personally, I think it is more likely that we have not found them because they are dim and we have not devoted enough instrument time to look for them. But, then again, perhaps the black holes gobbled them up.
70.116.68.198 06:56, 1 January 2006 (UTC)Don Granberry.
Maybe red dwarfs are population llll stars( Population lll stars with carbon) —Preceding unsigned comment added by Alexrybak ( talk • contribs) 17:16, 22 May 2011 (UTC)
Here is a very useful link:
http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v540n1/50350/50350.html
Somewhere along the way, their simulation runs must have butted heads with Xeno of Elea. They assume the existence of "dark matter" and a considerably less than homogenous cloud structure in the "early universe."
There is no suggestion that any non-linear, self-iterative processes were considered. Such large clouds of gasses would necessarily be affected by such processes. Quoting the above linked article:
"What will be the fate of the collapsing core? Within the core the number densities increase from 105 to 108 cm-3. For densities ≳108 cm-3, however, three-body formation of H2 will become the dominant formation mechanism, transforming all hydrogen into its molecular form (Palla et al. 1983). Our chemical reaction network does not include this reaction, and the solution cannot be correct at r ≲ 0.1 pc. The most interesting effect of the three-body reaction is that it will increase the cooling rate by a factor of ∼103, leading to a further dramatic density enhancement within the core. This will decrease the dynamical timescales to ≪100 yr, effectively decoupling the evolution of the fragment from the evolution of its host primordial molecular cloud. Therefore, it is a firm conclusion that only the gas within these cores can participate in Population III star formation."
The model used relies non-local thermodynamic equilibrium and this can be problematic.
http://www.physics.usyd.edu.au/astron/iau189/toc-posters.ps
Also, the one description of the nucleosynthesis process in Population III stars that I could access assumes that the stars are not rotating.
The upshot is that we appear to be placing a wee bit too much faith in a computing model limited by computing resources, particularly when it is claimed that only very large stars (30 to 1000 solar masses) were made during this period of cosmological history and that none of those stars were in rotation.
While this IS a good working theory on which to foot further investigations, the investigators seem to be entirely too eager to comply with pre-conceived notions. In court they would be accused of "assuming facts not in evidence." Rather than being an effort to discover the nature of stars that formed during the early periods of the universe, assuming the universe had an "early period", this seems to be an attempt to shore up a problem ridden model of the universe.
The current cosmological model may one day be shown to be correct, but dogmatic adherence to it prior to such a demonstration strikes me as being a very poor procedure. While a sincere search for very old red dwarfs or K stars of Population III origin would be arduous, it should nevertheless be carried out.
70.116.68.198 17:29, 1 January 2006 (UTC)Don Granberry
Do Red Dwarfs have any carbon within them? Zachorious 05:09, 31 July 2006 (UTC)
All observed red dwarfs contain carbon. Carbon is in the top 5 most abundant elements in the Universe. It is likely that the only red dwarfs which contain no carbon belong to Population III. If such stars still exist they are may have accreated material from the interstellar medium or a companion star and so contain at least a tiny amount of carbon. You may be interested in the extremely iron deficient star HE 1327-2326, which has an iron to hydrogen ratio of 1/250000 of the solar value.
Carbon?Aha!Carbon in outer layers,NOT IN THE CORE! —Preceding unsigned comment added by Alexrybak ( talk • contribs) 17:08, 22 May 2011 (UTC)
This statement does not seem right to me
Since a low mass star fuses hydrogen in the presence of metals, then an early protostar of such a low mass devoid of metals would not 'go nuclear', it would simply sit around as a clump of gas until more material came along. |
I assume 'fuses hydrogen in the presence of metals' refers to the carbon-nitrogen-oxygen (CNO) cycle in which fusion is catalysed by C,N and O. However, the CNO cycle does not become efficient until temperatures in excess of around 16 million Kelvin are reached. On the Main Sequence, such temperatures are only reached in stars of greater than about 1 solar mass. For low mass stars (and the Sun) the main fusion reactions which occur are those of the proton-proton (PP) chains. The PP-chains do not require the presence of metals, so Population III red dwarfs can exist.
I believe it was a children's television programme. I suggest we change the link to say: "For the British children's television programme from the 1980s..." - — Preceding unsigned comment added by 138.37.7.247 ( talk)
Is life probable on planet that revolves around a red dwarf ? —The preceding unsigned comment was added by 64.18.179.229 ( talk) 20:17, 2 March 2007 (UTC).
I am probably doing this wrong as I have never done anything to a Wiki, but I was curious in this article how it is mentioned that one of the difficulties in supporting life around a Red Dwarf was due to the fact that little to no UV radiation was emitted by such a star. However in this article from Space.com "Can Life Thrive Around A Red Dwarf Star" http://www.space.com/scienceastronomy/090409-sm-reddwarf-life.html It states that the difficulty is that UV radiation can be 100-10,000 more than normal. Well, if there were little to no UV radiation than 10,000 times more than almost none shouldn't necessarily be so big a concern. I feel like this entire article is full of factual errors, just based on scanning this discussion page and reading articles from more reputable sources. This is a much more glaring error than say the artist rendition error mentioned above. Someone who knows more should really fix this before misinformation can confuse too many people. —Preceding unsigned comment added by 184.56.26.53 ( talk) 14:53, 10 December 2010 (UTC)
There's all sorts of issues in this area. Tidal Locked planets are still being described as if the have very thin to no atmospheres, which might be an issue for life, since that's the only way to get massive temperature differences. Since we have Venus to see what happens when you have a very slow rotation and a thick atmosphere. At least it's been given the "could" designation. — Preceding unsigned comment added by 68.107.138.23 ( talk) 19:23, 18 May 2018 (UTC)
Why are the links to other articles in this page red? 140.198.172.119 17:52, 10 May 2007 (UTC)
Hi, what happens when a red dwarf runs out of hydrogen? Are they massive enough to swich to helium fusion and become red giants, as the sun will in 5 thousand million years (sorry, still reluctant to adopt the short scale)? Yeah, I know no the universe is too young for a red dwarf to have run out of fuel anyway, but I am just curious... Steinbach (fka Caesarion) 15:21, 12 May 2007 (UTC)
The article on stellar evolution states that 'A star of less than about 0.5 solar mass will never be able to fuse helium even after the core ceases hydrogen fusion' however apparently if the core is not fully convective - i.e. if there are stratified layers inside the star then 'it will develop into a red giant ... but never fuse helium as they do; otherwise, it will simply contract until electron degeneracy pressure halts its collapse, thus directly turning into a white dwarf.' -- Neo 21:18, 12 May 2007 (UTC)
I thought that the White dwarf stars gradually cool to become Red dwarf stars, on their way to evolving into Black dwarf stars... is that true, or are these completely separate stars, like Brown dwarf and Sub-brown dwarf stars? (i'm asking becuase i was taught that stars go from white to red to black in grade 5, but i was always skeptical of that. RingtailedFox • Talk • Stalk 17:18, 12 May 2007 (UTC)
SOmeone more knowledgeable than me needs to re-add the Planets section. I just blanked it because other than the heading Planets the section was empty except for the words, "Eat anus." Basejumper2 12:54, 25 October 2007 (UTC)
I’m fine with this change. It’s correct since the detecting went mostly for plants. -- DavidD4scnrt ( talk) 06:59, 10 April 2008 (UTC)
The planets here are only the new ones from 2005 and later. There are several planets orbiting red dwarfs, so I think we should create an article called: List of red dwarf planetary systems or something. I'll try to gather up enough info for it. -- UltimateDarkloid ( talk) 12:23, 15 September 2008 (UTC)
Gliese 370 b is mentioned at the end of the planets section but Gliese 370 isn't an M dwarf, or even a late k dwarf, it's a K5V and so doesn't that make Gliese 370 an orange dwarf star? Perhaps, if you want to mention it anywhere it should maybe be put into the K-type main-sequence star article. — Preceding unsigned comment added by 86.128.86.65 ( talk) 03:00, 24 March 2012 (UTC)
This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 10:02, 10 November 2007 (UTC)
That "artist's conception" of a red dwarf is simply far too red. An ordinary incandescent tungsten light bulb radiates at about half the temperature of a red dwarf. Its light is a soft yellow-orange-white against daylight and comparatively nearly white at night. Red dwarf stars just aren't that ... red. 68Kustom ( talk) 15:39, 5 September 2008 (UTC)
Depends on the Spectral type and mass of the Red Dwarf. There are those that are dim and look almost like Brown Dwarfs and those that are slightly orangish, -- UltimateDarkloid ( talk) 12:23, 15 September 2008 (UTC)
I think the general conception of the noun phrase "red dwarf star" gives the impression that "red dwarf stars" are stars that are very tiny and red. Not so. I believe "red dwarf star" are low mass stars that are fully convective and not giants, i.e. only fusing hydrogen to helium, not helium to carbon (nor oxygen). They're residing on the lower "red" end of the Hertzsprung-Russell diagram, which is the lower red extension of the main sequence. They're pinkish and orangeish because of low surface temperature, which translates to "red" in astronomy jargon. Rursus dixit. ( mbork3!) 08:49, 20 November 2010 (UTC)
I was curious as to the difference between Red dwarfs, Brown dwarfs and White dwarfs. Each of the three articles rarely or never mention the others, although it's natural to assume there's a similarity. From what I've read of the three:
• Red dwarfs are full-on stars, just small, maybe can't do helium fusion.
• Brown dwarfs are smaller still, can't even fuse hydrogen, but can participate in some lame fusion reactions, if they're lucky. Their surface temperatures range down to room temperature! Their sizes range down to gas giant planets.
• White dwarfs are supernova remnants; totally different from the other two. They often have surface temperatures comparable to stars (hence 'white') from residual heat; can't do fusion. If they get bigger, 1.44M☉, they become neutron stars (after maybe a supernova). (And neutron stars similarly become black holes beyond 3M☉.)
I'd prefer if a professional could supply and correct these guesses of mine in the article, maybe a separate section. Also the other two articles. OsamaBinLogin ( talk) 20:35, 11 May 2022 (UTC)
From Earth, no red dwarfs are visible to the naked eye.
Let's replace the subject "no red dwarfs" with "none"
None is not simply a singular combination of "no one". It can act as a plural for "not any". In this context, the subject (red dwarfs) is plural, and appears as plural in the sentence directly preceding. Therefore, the proper usage is "none are" which is plural. The user asked me to look it up, and I did before they told me and found several sites: [1] [2] [3] [4] The first time I read that sentence I knew it didn't sound right, and I was correct. "None is" is used for singular subject (Not one red dwarf IS visible to the naked eye) but in this case the preceding used plural, therefore it is No red dwarfs ARE visible to the naked eye. Cadiomals ( talk) 15:33, 28 September 2012 (UTC)
In the article on STARS, it is stated that low metallicity protostars with a mass of 87 x Jupiter's is the lower bound for star formation. Here, the lower bound is 0.075 x Sun's mass which is about a factor of 7 lower. I think this seeming discrepancy needs explanation. 216.96.76.236 ( talk) 22:23, 20 June 2013 (UTC)
The section "planets" ought be updated after the discovery of Kepler 186f 187.59.103.179 ( talk) 19:49, 19 April 2014 (UTC)
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There is a draft article called List of red dwarfs that is nearly complete. Could some editors familiar with this topic check it over and possibly get it ready for mainspace? Brad v 00:30, 11 June 2018 (UTC)
Every good article needs a definition. This article has one, but it isn't universally loved. Discuss. Lithopsian ( talk) 20:43, 5 June 2019 (UTC)
I am having trouble coming up with a rigorous source that is willing to commit to the least temperature a red dwarf could have. This seems to be partly because that number depends on chemical composition, and partly because it’s just really hard science, especially since late M dwarfs have a lot of dust production going on that helps obscure already faint signals. Several good papers explore the boundaries of red dwarf/brown dwarf transition as expressed by the LHS 1070 system (Köhler et al, 2012; Rajpurohit et al, 2012 for most recent), but they are unable to conclude whether LHS 1070B is a brown dwarf or a red dwarf. I infer by this that there isn’t much fusion going on in the lowest mass red dwarfs even though they are able to sustain it, and that therefore the transition is continuous between brown and red dwarf as far as measurable properties go—especially surface properties. That means the value is going to be known more from theory than from detection. Meanwhile the casual reader would probably like to have some number. I settled on ~2,500K on the basis of Köhler’s paper, but this would be for a Population I star, and I don’t find any numbers for Population II. I also perused endless lists of low mass stars, but (1) often they don’t state stellar vs brown dwarf; and (2) various sources often disagree considerably on the spectral type or surface temperature. Help? Strebe ( talk) 04:51, 7 June 2019 (UTC)
I am not in favor of this change in image. It’s hard to talk about “accuracy” in this context, given the impossibility of staring at the sun from a distance that would yield a comparable disc size, but in a relative sense, the new image doesn’t look significantly different from what a reader might expect of an image of our sun, other than the large sunspots. The previous image conveyed the comparatively dim nature of a red dwarf cogently. Strebe ( talk) 07:20, 17 May 2020 (UTC)
@ Lithopsian: this reversion was some kind of slip on my part. Sorry about that. Strebe ( talk) 00:46, 30 October 2021 (UTC)
There is an article for every other stellar class, except class G. Class G stars seem to instead be in the Red Dwarf article, even though not all red dwarfs are class G. — Preceding unsigned comment added by Empika1 ( talk • contribs) 00:29, 11 August 2022 (UTC)
Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT ( talk) 07:55, 17 January 2022 (UTC)
If you had a mixture of potent greenhouse gases (CH2O, CO2, and CH4) and a thick atmosphere, you could have a planet further away from the star and yet habitable, right? These gases absorb a lot in the mid-IR regions (>3 microns wavelength) but are mostly transparent at near-IR and at wavelengths below 3 microns or so. The energy from the star would thus mostly pass through, while the planet's own blackbody emission would be mostly re-absorbed. 209.104.252.130 ( talk) 17:19, 22 September 2022 (UTC)
![]() | This ![]() It is of interest to the following WikiProjects: | ||||||||||
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This article was the subject of a Wiki Education Foundation-supported course assignment, between 7 January 2019 and 25 April 2019. Further details are available
on the course page. Student editor(s):
KatepaImer.
It seems to me that if we have not observed any red dwarf stars with zero metal content, then we have indeed observed red dwarf stars that have moved off the main sequence and we are still left with the puzzle of determining the precise age of the universe. About all we can say for certain is that the universe should be much older than the estimates that are popular at the moment.
The reason I bring this up is because I cannot imagine how you find a red dwarf that has gone cold. It seems unlikely that they would become white dwarfs harboring degenerate matter. This is a case of an absence of something indicating a condition we have failed to properly conisider.
I disagree with this statement:
Red dwarfs never initiate helium fusion and so cannot become red giants |
Red giants, at least as expected with Sun-like stars, occur before the initiation of helium fusion, with shell hydrogen fusion. Although it might take more-then-the-current-age-of-the-Universe for red dwarfs to reach the point of having an inert helium core, I could imagine this state of affairs, at least with the bigger end of red dwarfs. Does anyone have any better information? Joffan 19:02, 16 September 2005 (UTC)
At the begining of the Main Sequence red dwarfs are fully convective. As a red dwarf ages the hydrogen to helium ratio decreases throughout the star. This forces the temperature of the core up to maintain the rate of fusion. At some point this causes a radiative shell to develop between a convective core and a convective exterior. The hydrogen outside the core is no longer available for fusion and the evolution proceeds rapidly. What happens next depends upon mass.
Disclaimer, much of what I have said above occurs on timescales greater than the age of the Universe, so is completely untestable. Thus this is more speculation than rigorous science. -- Ealdian 14:26, 17 August 2006 (UTC)
Actually, if a red dwarf has a mass greater than 0.4 mass of the Sun, not all of the star’s region is convection zone and it could become a red giant. —- Anonymous 17:38, 29 June 2019 — Preceding unsigned comment added by 2402:800:61B1:773A:1464:BA3B:13D2:A65D ( talk)
Stars of extremely high mass that burned out quickly, by cosmological standards, and thereby created all the metals needed for the current crop of Population II and Population I stars. Shouldn't this have left us with a very high number of neutron stars, magnetars, and black holes? Wouldn't the consequences of having a large number of such objects around be rather serious?
Here, I am not criticizing Wikipedia as this seems to be an accurate exposition of current theory. Nevertheless, I do have serious misgivings about the theory. Granted, Astronomers, Astrophysicists, and Comologists need a theory to work with and from, but they seem terribly cocksure at times.
Quoting the article on Pop III stars here, because I cannot get the talk tab to work on that article:
"If these stars were able to form properly, their lifespan would be extremely short, certainly less than one million years. As they can no longer form today, viewing one would require us to look to the very edges of the observable universe. (Since the time it takes light to reach Earth from great distances is extremely long, it is possile to see "back in time" by looking farther away.) Seeing this distance while still being able to resolve a star could prove difficult even for the James Webb Space Telescope."
If the theory concerning these putative stars is in any way correct, then JWST should be able to view entire galaxies of such stars, yes? The spectra of nearly all the stars should all be very nearly the same, depending upon the age of the putative galaxies of Pop III stars. In fact I would expect the spectra of such young galaxies to fall into "bins" according to their ages. A galaxy only one million years old should be easily distinguishable from one that is slightly older than one million years and so on until all the Pop III stars have had time to burn out. Metalicity galaxy wide should increase with age in almost stair-step fashion.
It amazes me, by the way, that something around one percent or less of elements heavier than helium can have such profound effects on stellar size. Current counts suggest that the overwhelming majority of Pop II and Pop I stars are K to M class dwarfs. Why the anticipated paucity of such stars in Pop III? Simply because we have not found any such stars that have turned off the main sequence?
Personally, I think it is more likely that we have not found them because they are dim and we have not devoted enough instrument time to look for them. But, then again, perhaps the black holes gobbled them up.
70.116.68.198 06:56, 1 January 2006 (UTC)Don Granberry.
Maybe red dwarfs are population llll stars( Population lll stars with carbon) —Preceding unsigned comment added by Alexrybak ( talk • contribs) 17:16, 22 May 2011 (UTC)
Here is a very useful link:
http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v540n1/50350/50350.html
Somewhere along the way, their simulation runs must have butted heads with Xeno of Elea. They assume the existence of "dark matter" and a considerably less than homogenous cloud structure in the "early universe."
There is no suggestion that any non-linear, self-iterative processes were considered. Such large clouds of gasses would necessarily be affected by such processes. Quoting the above linked article:
"What will be the fate of the collapsing core? Within the core the number densities increase from 105 to 108 cm-3. For densities ≳108 cm-3, however, three-body formation of H2 will become the dominant formation mechanism, transforming all hydrogen into its molecular form (Palla et al. 1983). Our chemical reaction network does not include this reaction, and the solution cannot be correct at r ≲ 0.1 pc. The most interesting effect of the three-body reaction is that it will increase the cooling rate by a factor of ∼103, leading to a further dramatic density enhancement within the core. This will decrease the dynamical timescales to ≪100 yr, effectively decoupling the evolution of the fragment from the evolution of its host primordial molecular cloud. Therefore, it is a firm conclusion that only the gas within these cores can participate in Population III star formation."
The model used relies non-local thermodynamic equilibrium and this can be problematic.
http://www.physics.usyd.edu.au/astron/iau189/toc-posters.ps
Also, the one description of the nucleosynthesis process in Population III stars that I could access assumes that the stars are not rotating.
The upshot is that we appear to be placing a wee bit too much faith in a computing model limited by computing resources, particularly when it is claimed that only very large stars (30 to 1000 solar masses) were made during this period of cosmological history and that none of those stars were in rotation.
While this IS a good working theory on which to foot further investigations, the investigators seem to be entirely too eager to comply with pre-conceived notions. In court they would be accused of "assuming facts not in evidence." Rather than being an effort to discover the nature of stars that formed during the early periods of the universe, assuming the universe had an "early period", this seems to be an attempt to shore up a problem ridden model of the universe.
The current cosmological model may one day be shown to be correct, but dogmatic adherence to it prior to such a demonstration strikes me as being a very poor procedure. While a sincere search for very old red dwarfs or K stars of Population III origin would be arduous, it should nevertheless be carried out.
70.116.68.198 17:29, 1 January 2006 (UTC)Don Granberry
Do Red Dwarfs have any carbon within them? Zachorious 05:09, 31 July 2006 (UTC)
All observed red dwarfs contain carbon. Carbon is in the top 5 most abundant elements in the Universe. It is likely that the only red dwarfs which contain no carbon belong to Population III. If such stars still exist they are may have accreated material from the interstellar medium or a companion star and so contain at least a tiny amount of carbon. You may be interested in the extremely iron deficient star HE 1327-2326, which has an iron to hydrogen ratio of 1/250000 of the solar value.
Carbon?Aha!Carbon in outer layers,NOT IN THE CORE! —Preceding unsigned comment added by Alexrybak ( talk • contribs) 17:08, 22 May 2011 (UTC)
This statement does not seem right to me
Since a low mass star fuses hydrogen in the presence of metals, then an early protostar of such a low mass devoid of metals would not 'go nuclear', it would simply sit around as a clump of gas until more material came along. |
I assume 'fuses hydrogen in the presence of metals' refers to the carbon-nitrogen-oxygen (CNO) cycle in which fusion is catalysed by C,N and O. However, the CNO cycle does not become efficient until temperatures in excess of around 16 million Kelvin are reached. On the Main Sequence, such temperatures are only reached in stars of greater than about 1 solar mass. For low mass stars (and the Sun) the main fusion reactions which occur are those of the proton-proton (PP) chains. The PP-chains do not require the presence of metals, so Population III red dwarfs can exist.
I believe it was a children's television programme. I suggest we change the link to say: "For the British children's television programme from the 1980s..." - — Preceding unsigned comment added by 138.37.7.247 ( talk)
Is life probable on planet that revolves around a red dwarf ? —The preceding unsigned comment was added by 64.18.179.229 ( talk) 20:17, 2 March 2007 (UTC).
I am probably doing this wrong as I have never done anything to a Wiki, but I was curious in this article how it is mentioned that one of the difficulties in supporting life around a Red Dwarf was due to the fact that little to no UV radiation was emitted by such a star. However in this article from Space.com "Can Life Thrive Around A Red Dwarf Star" http://www.space.com/scienceastronomy/090409-sm-reddwarf-life.html It states that the difficulty is that UV radiation can be 100-10,000 more than normal. Well, if there were little to no UV radiation than 10,000 times more than almost none shouldn't necessarily be so big a concern. I feel like this entire article is full of factual errors, just based on scanning this discussion page and reading articles from more reputable sources. This is a much more glaring error than say the artist rendition error mentioned above. Someone who knows more should really fix this before misinformation can confuse too many people. —Preceding unsigned comment added by 184.56.26.53 ( talk) 14:53, 10 December 2010 (UTC)
There's all sorts of issues in this area. Tidal Locked planets are still being described as if the have very thin to no atmospheres, which might be an issue for life, since that's the only way to get massive temperature differences. Since we have Venus to see what happens when you have a very slow rotation and a thick atmosphere. At least it's been given the "could" designation. — Preceding unsigned comment added by 68.107.138.23 ( talk) 19:23, 18 May 2018 (UTC)
Why are the links to other articles in this page red? 140.198.172.119 17:52, 10 May 2007 (UTC)
Hi, what happens when a red dwarf runs out of hydrogen? Are they massive enough to swich to helium fusion and become red giants, as the sun will in 5 thousand million years (sorry, still reluctant to adopt the short scale)? Yeah, I know no the universe is too young for a red dwarf to have run out of fuel anyway, but I am just curious... Steinbach (fka Caesarion) 15:21, 12 May 2007 (UTC)
The article on stellar evolution states that 'A star of less than about 0.5 solar mass will never be able to fuse helium even after the core ceases hydrogen fusion' however apparently if the core is not fully convective - i.e. if there are stratified layers inside the star then 'it will develop into a red giant ... but never fuse helium as they do; otherwise, it will simply contract until electron degeneracy pressure halts its collapse, thus directly turning into a white dwarf.' -- Neo 21:18, 12 May 2007 (UTC)
I thought that the White dwarf stars gradually cool to become Red dwarf stars, on their way to evolving into Black dwarf stars... is that true, or are these completely separate stars, like Brown dwarf and Sub-brown dwarf stars? (i'm asking becuase i was taught that stars go from white to red to black in grade 5, but i was always skeptical of that. RingtailedFox • Talk • Stalk 17:18, 12 May 2007 (UTC)
SOmeone more knowledgeable than me needs to re-add the Planets section. I just blanked it because other than the heading Planets the section was empty except for the words, "Eat anus." Basejumper2 12:54, 25 October 2007 (UTC)
I’m fine with this change. It’s correct since the detecting went mostly for plants. -- DavidD4scnrt ( talk) 06:59, 10 April 2008 (UTC)
The planets here are only the new ones from 2005 and later. There are several planets orbiting red dwarfs, so I think we should create an article called: List of red dwarf planetary systems or something. I'll try to gather up enough info for it. -- UltimateDarkloid ( talk) 12:23, 15 September 2008 (UTC)
Gliese 370 b is mentioned at the end of the planets section but Gliese 370 isn't an M dwarf, or even a late k dwarf, it's a K5V and so doesn't that make Gliese 370 an orange dwarf star? Perhaps, if you want to mention it anywhere it should maybe be put into the K-type main-sequence star article. — Preceding unsigned comment added by 86.128.86.65 ( talk) 03:00, 24 March 2012 (UTC)
This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 10:02, 10 November 2007 (UTC)
That "artist's conception" of a red dwarf is simply far too red. An ordinary incandescent tungsten light bulb radiates at about half the temperature of a red dwarf. Its light is a soft yellow-orange-white against daylight and comparatively nearly white at night. Red dwarf stars just aren't that ... red. 68Kustom ( talk) 15:39, 5 September 2008 (UTC)
Depends on the Spectral type and mass of the Red Dwarf. There are those that are dim and look almost like Brown Dwarfs and those that are slightly orangish, -- UltimateDarkloid ( talk) 12:23, 15 September 2008 (UTC)
I think the general conception of the noun phrase "red dwarf star" gives the impression that "red dwarf stars" are stars that are very tiny and red. Not so. I believe "red dwarf star" are low mass stars that are fully convective and not giants, i.e. only fusing hydrogen to helium, not helium to carbon (nor oxygen). They're residing on the lower "red" end of the Hertzsprung-Russell diagram, which is the lower red extension of the main sequence. They're pinkish and orangeish because of low surface temperature, which translates to "red" in astronomy jargon. Rursus dixit. ( mbork3!) 08:49, 20 November 2010 (UTC)
I was curious as to the difference between Red dwarfs, Brown dwarfs and White dwarfs. Each of the three articles rarely or never mention the others, although it's natural to assume there's a similarity. From what I've read of the three:
• Red dwarfs are full-on stars, just small, maybe can't do helium fusion.
• Brown dwarfs are smaller still, can't even fuse hydrogen, but can participate in some lame fusion reactions, if they're lucky. Their surface temperatures range down to room temperature! Their sizes range down to gas giant planets.
• White dwarfs are supernova remnants; totally different from the other two. They often have surface temperatures comparable to stars (hence 'white') from residual heat; can't do fusion. If they get bigger, 1.44M☉, they become neutron stars (after maybe a supernova). (And neutron stars similarly become black holes beyond 3M☉.)
I'd prefer if a professional could supply and correct these guesses of mine in the article, maybe a separate section. Also the other two articles. OsamaBinLogin ( talk) 20:35, 11 May 2022 (UTC)
From Earth, no red dwarfs are visible to the naked eye.
Let's replace the subject "no red dwarfs" with "none"
None is not simply a singular combination of "no one". It can act as a plural for "not any". In this context, the subject (red dwarfs) is plural, and appears as plural in the sentence directly preceding. Therefore, the proper usage is "none are" which is plural. The user asked me to look it up, and I did before they told me and found several sites: [1] [2] [3] [4] The first time I read that sentence I knew it didn't sound right, and I was correct. "None is" is used for singular subject (Not one red dwarf IS visible to the naked eye) but in this case the preceding used plural, therefore it is No red dwarfs ARE visible to the naked eye. Cadiomals ( talk) 15:33, 28 September 2012 (UTC)
In the article on STARS, it is stated that low metallicity protostars with a mass of 87 x Jupiter's is the lower bound for star formation. Here, the lower bound is 0.075 x Sun's mass which is about a factor of 7 lower. I think this seeming discrepancy needs explanation. 216.96.76.236 ( talk) 22:23, 20 June 2013 (UTC)
The section "planets" ought be updated after the discovery of Kepler 186f 187.59.103.179 ( talk) 19:49, 19 April 2014 (UTC)
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There is a draft article called List of red dwarfs that is nearly complete. Could some editors familiar with this topic check it over and possibly get it ready for mainspace? Brad v 00:30, 11 June 2018 (UTC)
Every good article needs a definition. This article has one, but it isn't universally loved. Discuss. Lithopsian ( talk) 20:43, 5 June 2019 (UTC)
I am having trouble coming up with a rigorous source that is willing to commit to the least temperature a red dwarf could have. This seems to be partly because that number depends on chemical composition, and partly because it’s just really hard science, especially since late M dwarfs have a lot of dust production going on that helps obscure already faint signals. Several good papers explore the boundaries of red dwarf/brown dwarf transition as expressed by the LHS 1070 system (Köhler et al, 2012; Rajpurohit et al, 2012 for most recent), but they are unable to conclude whether LHS 1070B is a brown dwarf or a red dwarf. I infer by this that there isn’t much fusion going on in the lowest mass red dwarfs even though they are able to sustain it, and that therefore the transition is continuous between brown and red dwarf as far as measurable properties go—especially surface properties. That means the value is going to be known more from theory than from detection. Meanwhile the casual reader would probably like to have some number. I settled on ~2,500K on the basis of Köhler’s paper, but this would be for a Population I star, and I don’t find any numbers for Population II. I also perused endless lists of low mass stars, but (1) often they don’t state stellar vs brown dwarf; and (2) various sources often disagree considerably on the spectral type or surface temperature. Help? Strebe ( talk) 04:51, 7 June 2019 (UTC)
I am not in favor of this change in image. It’s hard to talk about “accuracy” in this context, given the impossibility of staring at the sun from a distance that would yield a comparable disc size, but in a relative sense, the new image doesn’t look significantly different from what a reader might expect of an image of our sun, other than the large sunspots. The previous image conveyed the comparatively dim nature of a red dwarf cogently. Strebe ( talk) 07:20, 17 May 2020 (UTC)
@ Lithopsian: this reversion was some kind of slip on my part. Sorry about that. Strebe ( talk) 00:46, 30 October 2021 (UTC)
There is an article for every other stellar class, except class G. Class G stars seem to instead be in the Red Dwarf article, even though not all red dwarfs are class G. — Preceding unsigned comment added by Empika1 ( talk • contribs) 00:29, 11 August 2022 (UTC)
Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT ( talk) 07:55, 17 January 2022 (UTC)
If you had a mixture of potent greenhouse gases (CH2O, CO2, and CH4) and a thick atmosphere, you could have a planet further away from the star and yet habitable, right? These gases absorb a lot in the mid-IR regions (>3 microns wavelength) but are mostly transparent at near-IR and at wavelengths below 3 microns or so. The energy from the star would thus mostly pass through, while the planet's own blackbody emission would be mostly re-absorbed. 209.104.252.130 ( talk) 17:19, 22 September 2022 (UTC)