Talk:HD 209458 b

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Good article HD 209458 b has been listed as one of the Natural sciences good articles under the good article criteria. If you can improve it further, please do so. If it no longer meets these criteria, you can reassess it.
Article milestones
Date Process Result
March 11, 2006 Good article nominee Listed
February 20, 2009 Good article reassessment Kept
Current status: Good article
WikiProject Astronomy / Astronomical objects  (Rated GA-class, Mid-importance)
WikiProject icon HD 209458 b is within the scope of WikiProject Astronomy, which collaborates on articles related to Astronomy on Wikipedia.
 GA  This article has been rated as GA-Class on the project's quality scale.
 Mid  This article has been rated as Mid-importance on the project's importance scale.
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This article is supported by WikiProject Astronomical objects, which collaborates on articles related to astronomical objects.

Wiki Policy[edit]

GA Re-Review and In-line citations[edit]

Note: This article has a small number of in-line citations for an article of its size and currently would not pass criteria 2b.
Members of the Wikipedia:WikiProject Good articles are in the process of doing a re-review of current Good Article listings to ensure compliance with the standards of the Good Article Criteria. (Discussion of the changes and re-review can be found here). A significant change to the GA criteria is the mandatory use of some sort of in-line citation (In accordance to WP:CITE) to be used in order for an article to pass the verification and reference criteria. It is recommended that the article's editors take a look at the inclusion of in-line citations as well as how the article stacks up against the rest of the Good Article criteria. GA reviewers will give you at least a week's time from the date of this notice to work on the in-line citations before doing a full re-review and deciding if the article still merits being considered a Good Article or would need to be de-listed. If you have any questions, please don't hesitate to contact us on the Good Article project talk page or you may contact me personally. On behalf of the Good Articles Project, I want to thank you for all the time and effort that you have put into working on this article and improving the overall quality of the Wikipedia project. Agne 00:47, 26 September 2006 (UTC)

Pictures in public domain[edit]


Artist's concept illustrating Osiris' atmosphere loss

Do we have permission to use this? And if so, I'm sure the artist would like to get credit. --mav

This is public domain. Sennheiser checked the "i affirm that i have permission..." box when he uploaded. Sennheiser! 16:34, 8 Feb 2004 (UTC)
I can't find the source of the image anyway. (I should have pasted the address of the source, but I was newer than I am now) I found another image media:heic0403a.jpg from the ESA/hubblesite which is copyright free, and is a good illustration. We can replace the other one with this one. Sennheiser! 16:39, 8 Feb 2004 (UTC)
Wait, I found it!! --Sennheiser! 16:42, 8 Feb 2004 (UTC)
Very cool. Thanks! :) --mav

Article location[edit]

As 'Osiris' is just an unofficial nickname, I think this article would be better placed at HD209458 B, its official designation. Any objections to a move? Worldtraveller 16:11, 8 Feb 2005 (UTC)

I'd object, though not strenuously. According to Wikipedia:Naming conventions (common names), it's best to use the most common name for something. True, it suggests using the most common name that doesn't conflict with something (in this case there are several Osirises), but it also says "When choosing a name for a page ask yourself: What word would the average user of the Wikipedia put into the search engine?" I suspect most people wouldn't do a search for "HD 209458b" :) If you want to go ahead with the move anyway I won't raise a ruckus, though. Bryan 16:22, 8 Feb 2005 (UTC)
I'm inclined to support Bryan, albeit not very strenuously either. After looking at Category:Extrasolar planets and reading around the subject a bit, change to neutral / unqualified to opine. But pending a decision, I made HD209458 B a redirect. –Hajor 16:30, 8 Feb 2005 (UTC)
I take the point that the official name is not what people would be searching for! I'm just uncomfortable with an unofficial nickname being used as an article title. It's probably not a very good comparison, but for example the article on Prozac can be found at Fluoxetine, rather than Prozac which redirects, although it would be by far the better known name. If this one were moved, then searching for Osiris would still lead people to the article via the redirect.
In a similar case to this I had already moved Bellerophon (planet) to 51 Pegasi B having proposed it on that talk page a couple of weeks ago with no objections (no comment at all, in fact), but happy to leave this one alone if objections remain. Worldtraveller 19:23, 8 Feb 2005 (UTC)
I think there should be an exception made in this case, because if was the first time these measurements have been made this particular planet may need a more applicable name. I'm all for having the name of the article show the planets true designation, the less common (but perhaps more well known) name could be the redirect. Wikipedia is after all a site for clarifying information, even when there is little information to go by. Just my oppinion :PMonat 0715, 27 Nov 2006 (EST)

Name / Nickname / "Informal name"[edit]

"HD 209458 b is informally known as Osiris, though this name was not given by the astronomers credited with its discovery or accepted by the International Astronomical Union." -- So then how and with whom did this name originate? The links provided ([1][2]) don't seem to obviously provide this information. -- Writtenonsand 15:14, 11 April 2007 (UTC)

If memory serves, it got the nickname due to its star ripping away its atmosphere, like Set dismembered Osiris in Egyptian mythology. Who gave it that name, and when, is a mystery to me. --Trinexx 21:38, 10 June 2007 (UTC)

I'm an astronomer working on transiting extrasolar planets and HD 209458b comes up in conversation several times a week. Not once in the past decade have I heard the planet referred to as Osiris, except for in this wikipedia article and one scientific paper that coined the nickname. The planet has been mentioned in literally thousands of scientific papers, and all but one make no mention of the name Osiris. I think there is an unfortunate amount of disconnect between people who actively research HD 209458b and those who have kindly contributed to this article; Much of this disconnect can be attributed to the laughable references to this unused name "Osiris." It is time that this wikipedia article removes any mention to "Osiris." (talk) —Preceding undated comment added 02:27, 7 November 2009 (UTC).

The name came up in 2010... SpaceDaily story. (talk) 08:56, 24 June 2010 (UTC)
I searched for "Osiris (planet)", handily auto-completed by the search box, after seeing it mentioned on TV. I'm glad I could easily find it easily. I would certainly agree that the "informality" be clearly indicated as being used by non-professionals only, but I'm glad I could find it using the name as on TV so would not want that missing. Długosz (talk) 00:18, 20 July 2012 (UTC)


  • Support the move. Actually, Wikipedia prefers to use common names, rather than official names. However in this case, I believe HD 209458b actually is more common. For instance the recent news media stories about detection of light from this planet used "HD 209458b" and didn't mention Osiris... see [3]. -- Curps 04:06, 25 Mar 2005 (UTC)
  • Oppose, for the reasons I stated up in #Article location. "Osiris" is easier for us humans to remember, say in conversaion, etc. than a string of numbers is. Bryan 04:53, 25 Mar 2005 (UTC)
    • But it doesn't seem to be in actual use. Just a few days ago, it was announced that light from this planet had been directly imaged using the Spitzer Space Telescope, and the news stories in the media mostly never mentioned "Osiris". It seems this unofficial name never caught on... not surprising since extrasolar planets are now being discovered in bunches and most of them will just be named based on their parent star designation rather than being given any mythological name. -- Curps 09:57, 25 Mar 2005 (UTC)
      • Support, I agree with Curps. But name the article as HD 209458 b instead, as other extrasolar planets are designated in similar way (HD 209458b is not wrong, though). One thing about the naming of extrasolar planets: It is very unlikely that they will ever get proper names as it is expected that during the next decade there will be tens of thousands of new planets discovered. --Jyril 11:01, Mar 25, 2005 (UTC)
  • Support the move - as noted by Curps, the nickname is very rarely used. Worldtraveller 12:45, 25 Mar 2005 (UTC)

This article has been renamed as the result of a move request. violet/riga (t) 22:07, 30 Mar 2005 (UTC)

The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

The Planet[edit]


I think an estimate of when Osiris becomes a Cthonian planet would be in order. A statement of some astronomer would be best, but if that can't be found, we can do a simple calculation based on the rate of loss and the size of the atmosphere. I tried doing it, but my result is about 4 trillion years (either I am too stupid to do simple math, or Osiris is relatively safe), ignoring that helium (BTW, there must be some helium, why it's not mentioned in the article), oxygen, carbon would have a different loss rate, ignoring the possibility of an orbit change and assuming the rate of atmosphere loss remains constant. 18:39, 27 Nov 2004 (UTC)

Your calculation is correct, "10,000 tonnes of hydrogen per second" is far too low (!) to cause any appreciable loss of hydrogen, even after billions of years (4 thousand billion years to lose all its mass, or ~300 universe lifetimes, or a mere 150 lifetimes, if only half is hydrogen). Hence I question either the 10,000 or the implication of a Cthonian fate here. -Wikibob | Talk 04:20, 2005 Apr 2 (UTC)
I found a conference paper which appears to be the only reference to Chthonian planets in the astronomical literature - [4] - they give the evaporation rate as 100,000 to 500,000 tonnes/s, so it looks like a 0 may have got dropped at some point. At this rate they reckon the planet will have lost 1-7% of its mass over a lifetime of 5 billion years. So, not negligible, but not in danger of losing all of its atmosphere, it would seem. I'll add some info to the article. Worldtraveller 11:14, 2 Apr 2005 (UTC)
A paper published later in 2004 May 18, Numerical simulations of hydrodynamic evaporation of short periodic giant exoplanets in the light of Roche lobe effects, describes a model that gives "a maximum rate of 6 × 10^10 g s-1" for hydrogen loss. This is 6 1 E 7 kg, or 60000 tonnes, per second. This would only cause a loss of around a half a percent of its mass over 5 billion years. However I have not added this ref to the article for now. -Wikibob 17:57, 24 December 2005 (UTC)
Replying to myself, searching the Notes for HD 209458, there are several papers discussing how certain exoplanets may suffer large losses due to evaporation, and one that points out it is incorrect to simply extrapolate a loss rate:
After reading these (and this one) I wonder if we are making estimates too soon, and should wait for more conclusive research results. -Wikibob 20:10, 24 December 2005 (UTC)
Given the potential for these estimates to change, is it possible to caption that gorgeous artwork with a particular rate of loss? The source page implies this is 10,000 tonnes per second, but doesn't actually say that the artist used this figure. Also, a fun question (though it may be beyond what Wikipedia can do for now) is what would things be like for the Earth and Moon if they orbited in the plane of a planet like that? Mike Serfas 17:14, 11 April 2007 (UTC)

Transit discoverers[edit]

The HD 209458 article says that teams led by Greg Henry and David Charbonneau first detected the transit of HD209458 b, this article mentions only David Charbonneau and Timothy Brown. According to the NASA press release [5], Greg Henry's group alone found the transit. It could be that NASA didn't know that Charbonneau too had detected the transit. Either way, these articles conflict with each other.--Jyril 10:29, 24 December 2005 (UTC)

According to IAUC 7307: HD 209458; SAX J1752.3-3138 dated 12th November 1999, Henry et al reported a transit ingress on Nov. 8.

Now David Charbonneau's paper Detection of Planetary Transits Across a Sun-like Star, dated November 19th, cited Henry's circular 7307, but state full transit observations were made on September 9 and 16. So it looks like David saw the transit first but published after Henry had published his later observation (and this would explain NASA not knowing about on November 14, 1999, the date of their press release -added by Wikibob 20:25 24 Dec 2005).

Accordingly I've added Henry's team to the article, and included these refs. -Wikibob 17:04, 24 December 2005 (UTC)

It's big, but... how big exactly?[edit]

We seem to be giving two separate mass measurements for this planet. From the first section:

Its mass is 220 times that of Earth's (0.7 Jupiter masses), which indicates that it is probably a gas giant.

And from #Physical parameters:

Spectroscopic analysis had shown that the planet had a mass about 0.6 times that of Jupiter.

Can we source either? Or am I misreading something? --MerovingianTalk 13:53, 11 April 2007 (UTC)

Okay, the Extrasolar Planets Encyclopedia says 0.69 Jupiter masses, +/- 0.05, so I guess that would make the first instance in our article (0.7) right. I have added the source. --MerovingianTalk 14:45, 11 April 2007 (UTC)
  • First line of paragraph 17 reads: "The small planet orbits its star every three and a half days, and each time it goes by, scientists can assess what is in its atmosphere by how it absorbs light from the star." .7 Jupiter mass and a greater volume than Jupiter does not a "small" planet make, by planetary standards.—Preceding unsigned comment added by Gdearien (talkcontribs) 14:44, 2007 April 11


Should we add the atmospheric information like planets in our solar system just without percentages?

Done. --Zimriel (talk) 17:50, 15 August 2008 (UTC)

Transit spectroscopy[edit]

The term we should be using when describing the water vapor discovery technique is transit spectroscopy (no article yet). This paper and this one both explain it quite well. Carcharoth 13:42, 12 April 2007 (UTC)


how could this article be documenting a current event if this planet is 7 mill light years away and it is observed by a spectroscope now?---Saince 15:04, 12 April 2007 (UTC)

Relatively speaking, it's in the news. I, for one, would prefer a tag that better expresses that relationship. --MerovingianTalk 17:29, 12 April 2007 (UTC)
Would {{Current-related}} be any better? —AySz88\^-^ 19:56, 12 April 2007 (UTC)
We could use that; do you think it would work to link the event part to #Atmospheric water vapor? --MerovingianTalk 16:55, 13 April 2007 (UTC)
The light is the only witness we have to the event. And from the light's perspective, this is happening now! (Special relativity, folks!) —The preceding unsigned comment was added by (talk) 00:00, 13 April 2007 (UTC).
It's only 150 light years removed from earth. 14:14, 14 April 2007 (UTC)

Chthonian planet[edit]

The article says that it is almost definitely a Chthonian planet, yet the actual articles on Shthonian planets says the opposite.

Well, this article is then wrong. HD 209458 b is a bloated gas giant, whereas the hypothetical Cthonian planets are solid former gas giants that have lost their gaseous outer layers. Fixed.— JyriL talk 10:55, 18 April 2007 (UTC)


Water Vapor or not?[edit]

The lead of the article includes a one sentence statement that water vapor has been detected, and cites a offer. However, items in the lead are supposed to be just a sumarry of items elsewhere. However, I can't find any further mention in the article of water being found. To the contrary, there is a description that an anticipated spectral peak from water was not found. Can anyone shed some light on this, please? Johntex\talk 14:46, 11 April 2007 (UTC)

I think I see the problem now. We just hadn't put the new info into the body of the article. I took a stab at it. Johntex\talk 15:00, 11 April 2007 (UTC)

Here might be a possible source of the discrepancy, quoted from Barman's paper:

"A detection of water in the limb of HD209458b is nominally at odds with a recent Spitzer IRS spectrum that shows no H2O features for this planet (Richardson et al. 2007). These data were taken during secondary eclipse and directly probe the planet’s dayside with negligible contribution from the limb. It is possible that the dayside atmosphere is nearly isothermal (Fortney et al. 2006) which would result in a spectrum with no detectable water absorption features, despite a copious water supply." (Barman, T 2007, 'Identification of Absorption Features in an Extrasolar Planet Atmosphere', accepted for publication in Astrophysical Journal Letters, preprint available at

What I interpret this to mean is this: Richardson obtained the spectrum by subtracting (star) from (star + planet dayside + atmosphere), obtaining (planet dayside + atmosphere), whereas Barman obtained the spectrum by subtracting (star) from (star + atmosphere), obtaining (atmosphere). Because atmospheric absorption features would be lost in the noise of a dayside spectrum, Richardson did not observe the features that Barman did. In other words, they were observing different events, one in which H2O lines could be effectively masked out. Someone42 11:25, 18 April 2007 (UTC)

Water vapor discovery question[edit]

This question seems a bit silly, but this discovery incidental or sought out. I.E., did the scientist say "I'm going to look for water vapor here," or did he discover it incidentally, i.e. "Hey - Is that water vapor?" --Jeffrey O. Gustafson - Shazaam! - <*> 16:01, 11 April 2007 (UTC)

Did you read the reference?[6]RJH (talk) 22:27, 11 April 2007 (UTC)
I still find that reference a bit confusing. For instance it says ' "And since I know exactly what physics and chemistry went into my simulation, I know precisely what caused those variations, and I can attribute those variations to water" or other molecules. '. What is the deal with the "or other molecules" at the end. Is that saying there is room to doubt what the moleucles are, or is it just confusing syntax by Johntex\talk 22:38, 11 April 2007 (UTC)
Well, "Barman found the water signature after applying new theoretical models he developed" suggests he was looking for it, and created a way to find it just for this case. --Jeffrey O. Gustafson - Shazaam! - <*> 23:05, 11 April 2007 (UTC)
Remember that they tried to find water here before, so yes, this latest attempt was to overcome the problems encountered when SST data was analysed to try and find evidence of water (2005) and the problems with the direct spectral observation (earlier in 2007). Third time lucky, I guess. Carcharoth 11:15, 12 April 2007 (UTC)

Water Vapor paragraphs[edit]

We have two paragraphs with almost-identical information, one under "Detection of the atmosphere", the other under "Direct spectral observation". The news kinda does fit under both headings, which probably means there should be a reorganization of the article. But in the meantime, I think it's better to keep everything under a single heading; so which would be better? —AySz88\^-^ 04:42, 12 April 2007 (UTC)

Three paragraphs now. <sigh>. New heading, I agree. Make it chronological, and please can someone make the correct link with the earlier, 2005, IR spectroscopy analysis using SST data? That was IR emitted by the planet. This HST data is absorption spectra of light emitted by the star and passing through the atmosphere edge-on and reaching Earth that way. Maybe a diagram is needed. Carcharoth 09:38, 12 April 2007 (UTC)
OK. Here is how I see it. Back in 2005 the first-ever IR analysis was done (see HD 209458 b#Direct detection). A later spectrum was observed earlier in 2007 (see HD 209458 b#Spectral observation). Unfortunately, the article now contains at least three separate paragraphs attempting to explaing the most recent 2007 analysis. I've rewritten and condensed them into HD 209458 b#Atmospheric water vapor. Carcharoth 09:55, 12 April 2007 (UTC)

"this hypothesis is still being investigated": what is the reference to this statement? Is it one of the cited footnotes? thanks Timb66 13:34, 18 April 2007 (UTC)

Atmosphere currents map[edit]

It looks like the atmosphere-currents map was just deleted due to copyright vio. I won't miss it. If I recall right, that map dated to 2003 or earlier. There is no way it matches any model that could be devised today, knowing what we know about the surface cloud albedo, stratosphere, chemicals etc. So good riddance I suppose. Still, I'd like to see a map on par with the one we have for HD 189733 b. --Zimriel (talk) 05:31, 28 August 2008 (UTC)

GA Sweeps Review: Pass[edit]

As part of the WikiProject Good Articles, we're doing sweeps to go over all of the current GAs and see if they still meet the GA criteria. I'm specifically going over all of the "Planets and Moons" articles. I believe the article currently meets the criteria and should remain listed as a Good article. I have made several minor corrections throughout the article. Altogether the article is well-written and is still in great shape after its passing in 2006. Continue to improve the article making sure all new information is properly sourced and neutral. I would recommend going through the article and looking into all of the statements that are similar to "As of April 2007..." that should be updated. I would also recommend going through all of the citations and updating the access dates and fixing any dead links. If you have any questions, let me know on my talk page and I'll get back to you as soon as I can. I have updated the article history to reflect this review. Happy editing! --Nehrams2020 (talk) 10:41, 20 February 2009 (UTC)

Assessment comment[edit]

The comment(s) below were originally left at Talk:HD 209458 b/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

I find this an Excellent and informative article. One minor observation and request for clarification; If this is a gas giant (and best evidence suggest that planets of this size and estimated density are), then how can it have a Surface temperature if it has no measurable surface? Are we talking about estimated temperature at the edge of the atmosphere? Or are we going by core temperature estimates? I would expect the core temperature to be much higher but I do not know. A citation would be helpful. Sean--Sean E. Gallagher 14:32, 12 April 2007 (UTC)

Last edited at 14:32, 12 April 2007 (UTC). Substituted at 16:55, 29 April 2016 (UTC)