Talk:Gliese 581

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Contents 1 Embargo 2 Data 3 Earthlike? 4 Extraterrestrial skies 5 Warp 5 6 Eccentricity 7 Age of the system ? 8 Nearby Stars 9 Pronunciation and rank 10 Image 11 Only "low mass" planet in a habitable zone? 12 What happened to 581a? 13 There are many... 14 Bias? 15 Peak wavelength? 16 Luminosity value 17 North? 18 Name of the Star?

[edit] Embargo

Hey eager-beavers, please respect the embargo. It's only another 6 hours. Vegasprof 17:38, 24 April 2007 (UTC)

Exactly what happens in 6 hours (from your post)? GoogleMe 18:26, 24 April 2007 (UTC)

There is news about a "new" Earth-like planet in this star's planetary system, see for example [1]. /195.58.126.131 18:32, 24 April 2007 (UTC)

Not exactly. Now it's four hours and two minutes. I put up a notice of this newly discovered planet on this page yesterday. The news was "embargoed," meaning that the press release was sent to media with a request not to print it until 19:00 ET today, which is four hours from now. One of the administrators deleted my post, and told me the situation, which I know fully understand and agree with. It's up to the discoverers to time their press release, and it was not nice for just a few papers to breach the embargo; the news was sent to them as a courtesy, so that they could ready their presses, or whatever. Anyway, despite the intense excitement about this story (which has already leaked to the Extrasolar Planets Encyclopedia) I think we should be polite and respect the embargo. Vegasprof 19:06, 24 April 2007 (UTC)

OK, I didn't fully understand that. Maybe it was an idea to prevent an article related to such an embargo from being updated by "locking" it? /195.58.126.131 19:12, 24 April 2007 (UTC)

Right. It has nothing to do with Wikipedia. But Wikipedia (as I understand), as a matter of courtesy, does not want to breach news embargoes. Vegasprof 19:18, 24 April 2007 (UTC)

19:00 ET probably refers to european time, i.e. it means 17:00 UTC, or 13:00 EST -- Stereo ^(talk) 21:45, 24 April 2007 (UTC)

Eastern, Central, or Western European time? If it was 17:000 UTC, the news would have appeared on the ESO website. CNN did have the news, but they removed it. So ET has to mean EST.— JyriL ^talk 22:04, 24 April 2007 (UTC)

Embargo is up now. Thanks for respecting the embargo - I removed the information as a courtesy, and I'm glad it was respected in the main. Daniel Bryant 01:24, 25 April 2007 (UTC)

[edit] Data

The Extrasolar Planets Encyclopaedia has the data available for the planets c and d.[2]— JyriL ^talk 22:06, 24 April 2007 (UTC)

The chart says the planets are in order by distance from the star, but aren't they actually in order of discovery? Egamble928 02:00, 25 April 2007 (UTC)

In this case, the order is same.— JyriL ^talk 16:15, 25 April 2007 (UTC)

[edit] Earthlike?

A planet far more massive than the earth, orbiting a much dimmer star than the sun, in 12 and some days.

Maybe it's near earth temperatures. Maybe it isn't.

Is this news? Is this accurate? Does wikipedia want to go here? —Preceding unsigned comment added by 66.18.209.190 (talk • contribs) 25 April, 2007

Actually, it IS news. I just saw it on the news here in Holland and I have read a (Dutch) article about it in the Volkskrant, a big daily newspaper here. There is talk about whether there could be live on this planet, since it is earth-like with moderate temperatures (between 0 and 40 degrees Centigrades) and the possibility of the existence of liquid water on the planet. MarioR 10:26, 25 April 2007 (UTC)

[edit] Extraterrestrial skies

What would one see in the sky when Gliese 581 b makes a transit of the sun (Gliese 581)? Would it appear as a dot over that sun, or would it completely eclipse the sun? Our sun, of course, would appear in the constellation Cetus. GBC 15:49, 25 April 2007 (UTC)

You mean, what would it look like from 581 c? A dot. Our sun and our moon each appear to cover half a degree of arc in the sky. Gliese 581 is roughly 0.4 times as big as Sol, but only 0.07 times as far from 581 c, so it appears quite large, 2.85 degrees of arc, about 5.7 times as big as Sol seen from Earth. 581 b, 0.003 times as big as Sol, when transiting, would be about 0.03 AU from 581 c; if Neptune-sized, that means 0.05 degrees, a tenth as big as the moon seen from Earth, a sixtieth of the size of Gliese 581. (If that eccentricity figure for 581 c in the table is right, though, 581 c gets much much closer, even crossing the orbit of 581 b, so b could appear much larger in the sky shortly before c's doomsday.) Also, if b is rocky rather than gaseous, it would be visually smaller still, say about 2/3 that size. Going to render it? Kaleja 18:34, 25 April 2007 (UTC)

[edit] Warp 5

88 days, not too shoddy, right?

I make it 60 days (365 * 20.5 / (5*5*5)) but at any rate, I haven't gotten my warp drive working yet. Kaleja 18:37, 25 April 2007 (UTC)

[edit] Eccentricity

The table on the Gliese 581 page gives a very high eccentricity of 0.3 for c's orbit; the page for Gliese 581 c gives eccentricity 0. Eccentricity 0.3 for a semimajor axis 0x 0.073 AU puts perihelion at about 0.039 AU if I got my math right; this is inside the orbit of Gliese 581 b, so I'm guessing that Gliese 581 c is more right than this page. Anyone have more info? Kaleja 18:14, 25 April 2007 (UTC)

Udry et al. give the choice between 0.0 and 0.16 for e_c (Table 1 on p. 4 in the preprint). Are we going to describe the circular case, the eccentric case or both? —xyzzy_n 20:05, 25 April 2007 (UTC)

The .3 came from me, but it was wrong. But it looks like .16 +/-.07 is right, that is the same on exoplanets encyclopedia. Sorry for the error, I was trying to sync up the page with 581 c and I was usign data someone else had posted. Looks like it is all straightened out now. Also it appears all the data matche's exoplante encyclopedia, should we cite them as the source? I think we should cite something. Rich.lewis 16:27, 27 April 2007 (UTC)

I took the data from the Udry et al. paper (with some rounding). We already cite it. —xyzzy_n 23:19, 27 April 2007 (UTC)

[edit] Age of the system ?

I can't find any estimated age of the star or planetary system. Age is of course relevant when considering the chances of life on the planet.

Yes, this is very important. In particular, it could take a billion years for a red dwarf star to 'settle down.' Yesterday, while compiling information for this article, I ran across the statement (in a reliable source) that Gliese 581 is 4.3 billion years old. I don't remember where I found it, but I can probably find it again. Vegasprof 00:07, 26 April 2007 (UTC)

The Urdy et al. 2007 Astronomy & Astrophysics pre-print discovery paper gives the age (but notes uncertainty of +- 1 Gyr). Michaelbusch 00:10, 26 April 2007 (UTC)

I found the age on exoplanets encyclopedis here, [3], but they reference a source article from the journal of astronomy and astrophysics. However, only the abstract is available without a subscription. The original source is cited as "The HARPS search for southern extra-solar planets, V. A 14 Earth-masses planet orbiting HD 4308" S. Udry1, et al. I can't verify the original source so I just added a citation to expolanets encyclopedia. Is that good enough? Should we cite the original source, even though we can't verify the citation (without a subscription to the journal)? I guess citing the exoplanets encyclopedia is better than nothing. Rich.lewis 16:21, 27 April 2007 (UTC)

It seems to me that HD4308 is not Gl581, and an other article about Gl581 gives 2 billion years to the age. I wrote to the editor of the exoplanets encíclopedia - no response.--157.181.47.247 15:19, 10 May 2007 (UTC)

[edit] Nearby Stars

I was hoping this article could point me to a list of other nearby stars. Mathiastck 07:05, 26 April 2007 (UTC)

Try http://www.solstation.com. GBC 15:56, 26 April 2007 (UTC)

Or try Lists of stars, or List of nearest stars — Jack · talk · 17:02, Thursday, 26 April 2007

[edit] Pronunciation and rank

Two questions: How do you pronounce the name of this star? And in terms of ranking amongst all other stars, how far away is it? — Jack · talk · 17:16, Thursday, 26 April 2007

OK, so it's pronounced [ˈgliːˌzə] — which is "glee-zer", right? — Jack · talk · 18:25, Thursday, 26 April 2007

Depends on your local dialect of English. Rhymes with "Condoleezza" for all speakers. 24.20.137.228 13:55, 28 April 2007 (UTC)

It's a German surname, so check German phonology. I'm Finnish so I don't know. :)

581 is the star's ID number in Gliese Catalogue of Nearby Stars, compiled by astronomers Wilhelm Gliese and Hartmut Jahreiß. Star's ID in that catalogue is GJ 581 (GJ meaning Gliese-Jahreiß).

Stars have many names (catalogue ID's) so you may want to check SIMBAD database for others. In most of the Europe this star was known as HO Librae but that name is somewhat problematic in the English speaking world. :)

-- 212.213.204.99 18:54, 26 April 2007 (UTC)

At the distance of 6.28 pc (20.47 ly) Gliese 581 is the 87th closest star system.[4] — JyriL ^talk 21:57, 26 April 2007 (UTC)

Thankyou very much, JyriL :) — Jack · talk · 01:58, Sunday, 29 April 2007

[edit] Image

I realise quite well that ‘Celestia isn’t reality’. However, so far I’ve found only one image of the star which is real ( and that image is copyrighted and non-free. As for other images, I don’t see any advantage of the non-free art of Image:Phot-22a-07-normal.jpg versus some similar image made with Celestia that would justify using the non-free image. —xyzzy_n 23:39, 27 April 2007 (UTC)

I'd prefer a chart of some kind. An image of the star, unlabeled, is not particularly useful (it is just a point), although Sinbad would give you the necessary images under fair-use license. I'd really like the periodograms of the Doppler shift measurements, but those are in Udry's jurisdiction. Michaelbusch 02:40, 28 April 2007 (UTC)

Image:Phot-22a-07-normal.jpg is problematic not only in that it seems unlikely that any conjunction of those planets with a camera could produce that particular image but also in that the colors are all wrong. The star is far too red. Red dwarfs are "red" like camp fires or tungsten lamps, not like fire trucks. Even if the star looked like that, where is all the white light illuminating the planets coming from? 24.20.137.228 14:17, 28 April 2007 (UTC)

There is enough blue light being emitted that human eyes would adjust colorsense to compensate. That said, the disc of the star should then appear white except at the limb. Michaelbusch 15:58, 28 April 2007 (UTC)

What we really need now is a simple diagram of the orbits of the different planets.--Pharos 02:08, 29 April 2007 (UTC)

I agree with Pharos — Jack · talk · 02:41, Sunday, 29 April 2007

Okay we have a diagram up. Fusion7 15:37, 13 June 2007 (UTC)

[edit] Only "low mass" planet in a habitable zone?

There seems to be some question about whether this is or is not the first exoplanet in a habitable zone. No other examples are listed in the habitable zone article or any other reference I've seen yet. I think a sentence saying "this is notable because ..." should be as simple as possible, and if extra qualifications like "low mass" or "rocky" are necessary we should know what the "high mass" or "gaseous" examples are. 24.20.137.228 04:57, 29 April 2007 (UTC)

UPDATE: Astrophysics professor Greg Laughlin says HD 73526 c is a "room temperature gas giant" and HD 100777 b is "squarely in the habitable zone of its parent star". Somebody/me/whoever should probably mention something about these planets in Habitable zone. 24.20.137.228 12:55, 29 April 2007 (UTC)

[edit] What happened to 581a?

This article lists three planets, 581b, 581c, and 581d. Why was "a" skipped? Nik42 20:57, 25 May 2007 (UTC)

581a is skipped, as it can also mean the star itself. Anarchist42 21:08, 25 May 2007 (UTC)

Ah, okay. What a strange convention. On a related note, are the letters assigned in order of discovery rather than distance? Nik42 01:36, 26 May 2007 (UTC)

Order of discovery. Sagittarian Milky Way 01:03, 10 June 2007 (UTC)

[edit] There are many...

There are about 12 planets with Earthlike temperatures, and these are massive enough to have Earth's mass moons that could hold life.Gliese 581 c is overhyped, this planet will be almost certainly very hot.Using these blackbody calculations, you will get temperature -20 degress Cellsius for our Earth.

[edit] Bias?

This edit seems to have been made by someone with a bone to pick against exoplanets in general and this one in particular. For example, saying that:

Another fairy tale is possibly more appropriate to current exoplanet studies, termed the "Emperor's New Clothes Effect"

certainly seems to me like this person has a bias against "current exoplanet studies". Can there at least be reliable citations to back up this part of the article? 4.245.224.8 03:19, 13 June 2007 (UTC)

Interesting comment considering the original article stated that Gliese 581 c is both 50% larger than the Earth and also that it is rocky when it is scientifically impossible to give that evidence at present, let alone reference it. It's a circular argument. If the radius is like that, the density of an object of that mass must surely be that of rock, if it's rocky, then it'll be 50% bigger than Earth at that mass. No reference was given for those statements in the original article.

In fact the whole original entry was riddled with super Earth bias of which there is little or no evidence even in the published scientific papers. Look at a solar system illustration placing earth adjacent to Neptune in terms of size, and imagine this third of a neptune minimum mass object , 5 x earth's mass, between the two.

It's simple. Wikipedia's own Spectroscopic binary data gives clues to how radial velocity work is done. Mass limits so derived are lower mass limits. They cannot be true in this instance as the object does not transit... ...unless a very recent press release on MOST satellite says different when the actual paper comes out.

Most exoplanet hype from the institutions is just that, hype. There is little independent confirmation except for the handful of transiting objects, most of the values have large scatter on their errors, including the distances, and the best fudged numbers are given. Most of the statements in the wikipedia entry on c were not referenced directly.

I'm not so much biased as anti-biased, or biased squared if you prefer. You've taken a propoganda bias and quoted it verbatim. Most of the data does not support statements as _exact_ as those made. I know encyclopedic entries are more general and not as specialised as niche and dedicated articles, but as the mass, size and nature of this object is purest speculation even given the formal data, noises about habitable zones and frost lines are perforce speculation based upon speculation. The only known Goldilocks Zone is in the Solar System, evidently this extrasolar system of Gliese 581 is not like the calibrating Solar System in anyway.

When it comes to reference the situation here is that the original statements had little specific reference to each attested fact anyway, whereas the points that can be pointed out as wrong are general facts, not usually referenced. For instance, SB1 spectroscopic binaries have their masses quoted as a ratio, an inclination dependent ratio, relative to the mass of the primary. Single red dwarf stars have their masses assumed, not measured, via a luminosity relation that is not the same for red dwarfs as other main sequence stars, and carries several differing values in the literature. The apparent magnitude and the parallax of this object, Gliese 581, are well known enough for an absolute magnitude to be derived, and thus the luminosity. Which mass relation is then used? Further, it may be that there are two such relations for red dwarfs, as can be seen by differing absolute magnitudes for differing objects, for example Proxima Centauri and Barnard's star, which are likely listed in wikipedia. And yet some assumption on this mass is taken for the red dwarf, that is used with the radial velocity data to assume a minimum mass for object c, which in itself is not the real mass as then it'd be at 90 degrees inclination, and thus eclipsing/transiting. Etcetera, etcetera, standard, general principles, stuff. This could shift the object's mass all over the place, if proper error ranges are considered. Therefore, Emperor's New Clothes. The original article carried the unfounded bias.

Finally, it is interesting to note that the similar generalized, not rigorously referenced, comments and changes I made with respect to the fact Gliese 581 is in fact not variable, despite what the reference catalogues say, was not excised for bias, likely because it makes the case for "life" out there more feasible. Feh.

Whatever, do what ya want, it's your wiki. Just don't accuse something assessing the bias of massive unsubstantiated speculation being passed off as concrete fact as being bias itself. How can you disprove something that is itself unproven? As the saying goes "it's not even wrong".

86.137.132.151 22:23, 13 June 2007 (UTC)

I agree that, with our current technology, anything that humankind can say about other solar systems and the planets within them is, at best, based on educated guessing and speculation. However, I think that this is implicit in the fact that we are talking about heavenly bodies several light-years away. Upon close inspection of your edit (and your defense of it up above), you seem to be saying that we cannot be sure of the exact details (mass and radius) of Gliese 581c, generally because of the fact that we probably do not lie in its orbital plane (and thus cannot observe it in transit, like we can with, for example, Venus) and because we are not very certain of the mass of its parent star (because it is a guess based on luminosity).

You also seem to be familiar with the mathematics behind these astronomical observations. If you can rewrite your edit in clear and simple terms that a plebian such as myself can understand, and add citations which can back up what you say when you can do so (for example, why it is not reliable to assume mass given the luminosity of a red dwarf star), and put it in a way that is neutral as to the possibility of life being there (which you seem to be against), and write it in such a way that it doesn't look like original research, then that would be a whole lot better and I won't delete it the next time I'm "being bold". Or better yet, maybe you can start an article about uncertainty in exoplanet studies or something to that effect.

As far as not reverting your other edits - sorry, I'll be more of an ad hominem Nazi next time. ;) (just kidding) And it's not my wiki - it's our wiki, it belongs to the world. (the world of humans, I mean) 4.245.149.216 11:13, 14 June 2007 (UTC)

[edit] Peak wavelength?

Are there any spectra of Gliese 581 available from which we can get an empirical value, as opposed to assuming the star is a blackbody (an approximation that isn't too good for cool stars)? Chaos syndrome 19:14, 28 August 2007 (UTC)

The paper that is referenced to in wikipedia is evidently taking the star to be a black body hence the values quoted for the bolometric luminosity within it.

Cooler stars are more prone to stray from a black body proximation in their continuum due to molecular absorption bands, but for a red dwarf this should be relatively insignificant. Hopefully.

How would you ascertain this peak wavelength? It would not just be the highest bit of the plot, or the most intense wavelength if there were emission peaks, for instance.

81.129.250.131 18:19, 2 September 2007 (UTC)

[edit] Luminosity value

We seem to have an issue with a user (I assume it is one user with two IP addresses from the content of the edit summaries)

I have a dynamic IP, there's nothing I can do about that (I'd actually forgotten, too). 81.129.250.131 18:48, 2 September 2007 (UTC)

Maybe consider registering as a user here, makes some things easier. Chaos syndrome 19:53, 2 September 2007 (UTC)

who is insisting on changing the value of the luminosity from the quoted value in the literature to a value calculated by that user. The values differ by only 0.1% of the solar luminosity (literature value=1.3%, user's value=1.2%). Already this is pretty good agreement, and looking at the von Bloh paper "Habitability of super-Earths in Gliese 581" it appears the error on the quoted value is 0.2% of a solar luminosity anyway, so the values derived are essentially identical. Since the user's calculation supports the literature value (the discrepancy is probably negligible within the error margins anyway), I suggest we go with the literature luminosity as we can provide a verifiable citation to this value. Chaos syndrome 22:55, 30 August 2007 (UTC)

The difference is probably negligible, so the point is somewhat valid, as it is within the errors, however the relationships between the values are nonlinear, so small amounts can matter. Likely in this case, however, the nonlinearity makes the difference even more insignificant. It is sad, however, for an information resource to list values in a data box and note another value that is at odds with one derived from those values.

The more important points are two:-

i) Another reference (number 6), to the Bloh paper propagates the constant falsehood with respect to the mass of these planets. Only if this was an eclipsing/transiting system with an inclination of 90 degrees could the mass limits for the planets be valid. As such they are lower limits. The planets are more massive than that. Conjecture about surfaces and the like are mere conjecture, there is no evidence of any kind to state what the atmosphere or nature of these objects are, they could be big lumps of rock, they could be small, not mini, but small Neptunes, they could be Jupiters. There is absolutely no way of knowing with current data.

ii) The Bloh paper has no more academic validity than a blog entry. It states nowhere as to whether it has been either submitted and/or acceptable by a mainstream scientific journal, or any journal at all, and therefore it is not peer reviewed, and therefore I repeat it has no more validity than a random blog entry. Anyone can upload a paper to arxiv if one or their friends and/or associates is willing to endorse it, which is not the same as peer review, more like favours between pals. Checks in ADS abstracts search reveal the paper exists nowhere else. Great care has to be taken when using arxiv preprints are references. Until they are logged as having been accepted by a peer reviewed journal they are not standard accepted by the scientific community articles, they are just thoughts and opinions. It is interesting to note that the Bloh paper has a version one upped in May, and now a version two recently upped, yet still only existing as a fancy styled blog entry, there having apparently been no attempt to submit it to standard scientific publishing scrutiny inbetween times.

81.129.250.131 18:48, 2 September 2007 (UTC)

Regarding the von Bloh paper, the Extrasolar Planets Encyclopaedia lists the reference as being submitted to Astronomy and Astrophysics - see the references list here. Furthermore, a Google search reveals that the authors do have peer-reviewed publications in related areas (e.g. Werner von Bloh's publication list), so this isn't the case of some randoms submitting a non-reviewed paper to arXiv and thus gives it more validity than a random blog entry IMHO. Furthermore, what seems to be going on here is a combination of various different methods to determine the luminosity: while a given bolometric correction relationship may be good for statistical samples, it is not necessarily applicable to an individual star. Other determinations of the bolometric correction may give different results: for example, from the absolute bolometric magnitude given in Delfosse et al. 1998, I calculate a luminosity of 0.014 times solar. In any case the luminosity value and the magnitudes in the infobox are not inconsistent, as we have not specified the bolometric correction. Chaos syndrome 19:53, 2 September 2007 (UTC)

[edit] North?

The first paragraph, as of this date, includes the phrase, "It is about two degrees north of beta Librae . . ."

I've seen locations of celestial bodies described in this way before and have never understood what that meant. I decided to try to make a link in the above phrase as a way of educating myself, but was unable to discover (within Wikipedia, at least) an adequate explanation to which I could link. I found the Celestial pole article, which provides some context but doesn't provide a satisfying layman's explanation for how a celestial body could be described as being "north" of another celestial body, and what the "degrees" are. I assume that it has something to do with the axis around which earth-bound observers perceive the heavens to be rotating, but that's an assumption on my part and represents the extent of my education on the subject.

Part of my problem is that I don't have an adequate search term. I don't know what that system of notation is called, so I can't search for it by name. Can someone out there with a knowledge of astronomy help me (and, likely, other readers)? Perhaps Wikipedia already has an article on this subject but I've been unable to find it. —CKA3KA (Skazka) (talk) 22:22, 29 November 2007 (UTC)

'North of' means in the same direction to the north as geographical along the sky, pointing towards the north celestial pole. BlueEarth (talk) 00:37, 30 November 2007 (UTC)

[edit] Name of the Star?

I've just been doing a bit of research into Gliese 581 and have found that the star is also referred to as Wolf 562, so why is this alternate name not listed in this article? I know that all other star articles list all the other names, but I don't see this one here, so why not? (for confirmation of the name check out this page: [5]) --Hibernian (talk) 00:03, 7 February 2008 (UTC)

Ok since on one has said anything for ages I've just gone ahead and done it, because I'm pretty sure about it. If it is for some reason incorrect, then please say so. Also it would be an idea to turn Wolf 562 into a redirect to Gliese 581. --Hibernian (talk) 17:13, 30 April 2008 (UTC)