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102 +/-9 kg/m-3 ? wouldn't that be a density just 1/10th that of solid ice? Yes, I see that number in the referenced document [2], but it doesn't make sense to me. — Preceding unsigned comment added by (talk) 00:00, 30 March 2014 (UTC)

It is also a function of the porosity of the object. It is common for a comet to have a density much less than water. -- Kheider (talk) 17:47, 20 June 2014 (UTC)


Currently, the mass is given as “3.14×1012±0.21×1012 kg.” I think it would be more readable if it was given as “3.14±0.21×1012 kg.” Is there any rule on how to format in this case?

Your suggestion makes complete sense. I've gone ahead and applied the change. Huntster (t @ c) 10:13, 4 August 2014 (UTC)
Per this update, the mass is actually "1.0±0.1×1013 kg.” (The exact text is "Using 80 hours worth of tracking data between 6 August, since arriving at the comet, and up to 9 August, the RSI team made a first estimate of the comet’s mass as approximately 1x10^13 kg +/-10%, or about 10 trillion kilograms.") (talk) 20:13, 21 August 2014 (UTC)
Great find, I've updated the article accordingly. Huntster (t @ c) 01:17, 22 August 2014 (UTC)

Should we use an ESA image of the comet's surface?[edit]

Comet Churyumov–Gerasimenko is currently being explored by the European Space Agency's Rosetta space probe which has already taken numerous detailed photographs of the comet's surface and has revealed the incredibly bizarre and complex shape of its nucleus. It would of course be extremely informative to readers if we could illustrate the article with one of these photographs. Unfortunately, ESA images are released under a non-free license, which means that although we can use them on Wikipedia, we need a good justification for it.

User:Huntster has objected to including an ESA image because the article already has a free-licensed image of the comet. Hunster explains, "I interpret the non-free rules as meaning that when a freely licensed image of a subject is available, then regardless of the superiority of any non-free alternative, the free image must be used". I believe Hunster's interpretation is overly strict. As you can see the free image merely depicts the comet as a dot of light, whereas the ESA images show the details of its unique shape. I therefore propose that the ESA image must be used to illustrate the surface features of the comet which are invisible in the free image. This is not a matter of beautifying the article but of being informative about the subject since the shape of the comet's nucleus is so complex that it could not be conveyed adequately in words.

Hunster has proposed that I try to find out what the consensus is among users of the article, so my question to readers is: Do you think it is justifiable for us to use an ESA image of the comet's nucleus is in this article, or do you think we must use only the free image (in which the comet is a dot of light)? Thanks for your comments. Arsia Mons (talk) 16:09, 5 August 2014 (UTC)

  • I feel it would constitute fair use here as the remarkable shape of the comet is difficult to describe in text, and no free image showing the shape of the comet will be available in the foreseeable future. Bericht 16:20, 5 August 2014 (UTC)
  • I agree with a better image. Fair use would surely apply, in this instance? ESA's Image Copyright Notice states that they can be used for informational purposes, when properly credited. As long as one of these images are properly credited, once transferred to Commons Wikipedia, I don't see the problem. As this is the first close encounter with the comet, there is no other source for such a close-up image, right now. EP111 (talk) 17:44, 5 August 2014 (UTC)
No I'm afraid ESA images are not free enough for commons, this has been argued to death a number of times. ChiZeroOne (talk) 19:53, 5 August 2014 (UTC)
Would it be free enough to upload to Wikipedia, instead of Commons? I understand that Wikipedia can allow somewhat less restriction, under certain circumstances. WP:FREER could apply, if it was uploaded directly to Wikipedia. For example: a. Can this non-free content be replaced by a free version that has the same effect? No, because the surface of the object, and the outline, is not clearly visible in any free image. b. Could the subject be adequately conveyed by properly sourced text without using the non-free content at all? No. The object is non-uniform, and difficult to convey in a description by text, alone. EP111 (talk) 20:46, 5 August 2014 (UTC)
I hate to say it, but I disagree with your assessment of clause b, it's already being described in the media as a "rubber duck-shaped" which should serve as a quick lay description. Furthermore, creation of a simple free-use illustration would not be too onerous an undertaking, should more detail be required. -Oosh (talk) 06:59, 6 August 2014 (UTC)
Only early low resolution images were described as a rubber duckie. The high resolutions ones look nothing like a rubber duckie. -- Kheider (talk) 13:38, 6 August 2014 (UTC)
  • It is a very arguable point, the use of non-free material is a last resort and it does have strict requirements. There is a free image of the comet and so using a non-free image is difficult to justify. The bar is quite high, it's not merely about what you would like to illustrate. ChiZeroOne (talk) 19:46, 5 August 2014 (UTC)
    I would like to see one at ~200-350px, but I agree it would probably get removed by a wiki cop/enforcer. -- Kheider (talk) 20:42, 5 August 2014 (UTC)
  • If you look at the article describing the asteroid 21 Lutetia, you will see that an ESA image taken by the same spacecraft is used in the article, even though there are free images of 21 Lutetia which show the body as a speck of light ( -- Bericht (talkcontribs) 09:11, 6 August 2014 (UTC)
Yes, and after a deletion discussion at WP:Files for deletion/2010 July 11#File:Lutetia closest approach (Rosetta).jpg, it was kept. Thincat (talk) 12:28, 6 August 2014 (UTC)
The Lutetia image is also somewhat larger (2,103×2,078px) than the one which is currently in use in the 67P article (300×217px), and may also be considered more presentable, as it isn't so closely cropped. The format for the Lutetia image can also be applied to the 67P image, as that size format has implicit allowance too. EP111 (talk) 12:46, 7 August 2014 (UTC)

Requested move[edit]

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: not moved. Jenks24 (talk) 16:09, 14 August 2014 (UTC)

67P/Churyumov–GerasimenkoComet Churyumov–Gerasimenko – It is referred to more generally as Churyumov–Gerasimenko; even in the lead, it says "Comet Churyumov–Gerasimenko, officially designated 67P/Churyumov–Gerasimenko". Articles such as Halley's Comet, Comet Encke, and Comet Biela have similar leads. It seems like the official name with the prefix is used only for more obscure comets, but this comet is not very obscure as the Rosetta probe visited it. Llightex (talk) 08:35, 7 August 2014 (UTC)

It is a common comet that only gets to about apparent magnitude 10, and for all practical purposes really requires large binoculars or a small telescope to be seen. Comet Encke frequently reaches magnitude 6, which is near the naked eye limit. Comet Swift–Tuttle was as bright as Polaris in 1862, will be even brighter in 2126 (while also being 90 degrees from the Sun), and is the parent body of the famous Perseids. I am not sure 15 minutes of fame justifies a move and Comet Churyumov-Gerasimenko already re-directs to the article. -- Kheider (talk) 13:33, 7 August 2014 (UTC)
I've also noticed that "Comet 67P" tends to be used predominately in the English spoken media as broadcasters seem to have difficulty pronouncing the discoverers' names. Brave attempts are made, sometimes, often with catastrophic results! Huntster (t @ c) 14:22, 7 August 2014 (UTC)
Looking through, very few periodic comets are at a name without the numerical designation. Most of the ones that don't are comets known for a very long time where the designation is clearly less common than the short name. I don't see any desperate need to change the present situation as both alternatives link to the article. And frankly for most English speakers 67P is more memorable Churyumov–Gerasimenko, even before we start on pronunciation. ChiZeroOne (talk) 20:45, 7 August 2014 (UTC)
  • Oppose many of the articles I've read about the Rosetta mission use "67P/" format. -- (talk) 07:53, 8 August 2014 (UTC)

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

Mass changes after heliocentric orbit shift in 1959[edit]

Do we have any papers published that we could cite to improve the article on how the much-closer-to-the-Sun perihelion in the eight 6.45-year orbits of the Sun that 67P has made since 1959, when it's orbit was dramatically changed?

The article currently says this:

Orbital history
Comets are regularly nudged from one orbit to another when they encounter Jupiter in close proximity. Before 1959, Churyumov–Gerasimenko's perihelion distance was about 2.7 AU (400,000,000 km). In February 1959, a close encounter with Jupiter<ref name="jpl-close" /> moved its perihelion inward to about 1.3 AU (190,000,000 km), where it remains today.<ref name="Kinoshita" />

It would seem that the closer solar approach would result in much higher mass outflow rates of water/ice from the cometary mass on each solar approach. N2e (talk) 16:23, 8 August 2014 (UTC)

That also would depend on how close to the Sun the comet was in the even more distant past. Comets can spend 10,000 years bouncing around the inner solar system. -- Kheider (talk) 16:40, 8 August 2014 (UTC)

Image used unlikely to meet Wikipedia fair use standard[edit]

The image now at the infobox is of such a high resolution that I cannot believe it meets Wikipedia's fair use standard. Furthermore the image page description appears to contain the now incorrect claim:

It is believed that low-resolution copies of this image:
   taken directly from the ESA Multimedia Gallery,"


qualify as fair use under United States copyright law.

-84user (talk) 14:09, 10 August 2014 (UTC)

I have reverted the image to the low res version as it does not need to be high-res to be used as a fair-use thumbnail to illustrate the comet nucleus. -- Kheider (talk) 15:58, 10 August 2014 (UTC)

Rosetta NAVCAM images now available under a Creative Commons licence[edit]

It's done ! All ESA Rosetta NAVCAM images are licensed under CC BY-SA 3.0 IGO. Thank you dear ESA ! :) => . Sincerely, --Neptunia For talk with Neptunia 21:13, 4 November 2014 (UTC)

"How fast could 67P go around the earth?" is a trick question[edit]

   An otherwise reliable source asks "How fast is the comet traveling?", and answers "The comet is traveling 83,885 miles-per-hour.", which is pretty reasonable. But it continues "At that speed, it would take only 18 minutes to circle the Earth." which invites horribly misleading imagery: the arithmetic is right, for an object in uniform circular motion around the earth's equator, but that image gets the physics almost as wrong as when the Millennium Falcon made the Kessel Run in less than twelve parsecs: anything moving at such a speed parallel to the earth's surface can't stay close to the surface without expenditure of great amounts of energy in forcing it to stay close to the surface instead of tearing away along a path that is much closer to being a straight line than a circle. (We'd do better with "its speed at the time of the Philae mission was about 50 times that of an F-22 Raptor at full throttle.")
   It also describes "the comet, which itself is circling the sun at 83,885 miles per hour", altho what it is doing is not circling, but orbiting along an elliptical orbit that is so slim that it's hard to distinguish it from a parabolic one. (And its speed varies drastically with distance from the sun.)
   Our editors should watch out for confusing statements, in sources that may be unreliable re this topic -- even if we are used to trusting them as reliable on most topics.
--Jerzyt 10:03, 12 November 2014 (UTC)

I don't see how these things would be useful for this article anyway. --JorisvS (talk) 10:23, 12 November 2014 (UTC)

Gravity assist?[edit]

This article says:

Comets are regularly nudged from one orbit to another when they encounter Jupiter in close proximity using gravity assist.

But gravity assist says:

In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft...

It seems that one is talking about natural phenomena and the other is talking about an engineered process. Isn't this a problem? — Brianhe (talk) 17:19, 13 November 2014 (UTC)

Yes, I've been thinking about that passage. The only difference between them I have been able to find, is that gravity assists in their normal meaning are a planned trajectories, whereas natural objects' orbit of course aren't. But that's not really much of a difference. Then again "using gravity assist" does not really add any information there, so can safely be removed (the original sentence did not include it). --JorisvS (talk) 17:53, 13 November 2014 (UTC)

Original name - Russian or Ukrainian[edit]

Now, that's what I call international effort - one ethnic Ukrainian citizen of USSR discovers a comet on the plates developed using equipment that formed part of an observatory based in Kazakhstan SSR by second ethnic Ukrainian citizen of USSR, who currently is a citizen of Tajikistan! Hence - comet name is given in all 4 relevant languages with said names given in order of relevance and priority. Given the time, place and circumstances of comet's discovery what should be the appropriate language reference for the comet's original name - Russian or Ukrainian? Since the the comet received its original designation within the framework of then current Soviet and International astronomical attribution practice, I believe Russian should serve as the language of the original name. And, if this persists to be perceived an issue I would rather have the entire reference to the language of the comet's name taken down than to see an historically incorrect reference be kept. Soviet citizens discovered the comet, soviet authorities named the comet - Russian was the official language of the the USSR and of the official Soviet naming body at the time - therefore the name of the comet as it was assigned then was indeed specified in Russian. — Preceding unsigned comment added by (talkcontribs) 11:35, 14 November 2014‎

Because it is identical in both languages, can't we simply list it as being both Ukrainian and Russian (and the name of course only once)? --JorisvS (talk) 13:32, 15 November 2014 (UTC)
I specifically mean saying something like "Russian and Ukrainian: Комета Чурюмова — Герасименко", not "Russian: Комета Чурюмова — Герасименко, Ukrainian: Комета Чурюмова — Герасименко", because the latter is needlessly long and does not really show that its name is the same in both languages. --JorisvS (talk) 13:39, 17 November 2014 (UTC)
Actually what is not identical is the spelling of the first name. If we follow the Ukrainian it should be Svitlana rather than Svetlana. I left a comment at Talk:Svetlana Gerasimenko. Tkuvho (talk) 14:42, 17 November 2014 (UTC)
Okay, but that has no bearing on the comet's name. --JorisvS (talk) 16:46, 17 November 2014 (UTC)

Yes check.svg Done - FWIW - added => "(Russian and Ukrainian: Комета Чурюмова — Герасименко," - hope this helps in some way - in any case - Enjoy! :) Drbogdan (talk) 17:03, 17 November 2014 (UTC)


Apparently the French observed the asteroid in august of the same year but it was named after Ch-G anyway. Should this be reported? Tkuvho (talk) 15:08, 18 November 2014 (UTC)

Observing the object and recognizing it as a newly found object (why exactly do you call it an "asteroid"), observing a comet and calculating its orbit in order to definitively establish it is as a newly observed comet - these separate casual observers who simply happen to glance upon the sky using whatever equipment they chance to have at the time from true discoverers. This does not need to be "reported" but simply added, so that an emphasis is given to the fact that celestial objects are very often "prediscovered" but are not recognized as anything new and therefore only those who have observed the object, understood its nature and computed its orbit are accepted as the discoverers. There is no contradiction - French astronomers ("by the way" number one - there are names and dates and references and links, right?) who merely "observed" ("by the way" number two - what exactly do your sources say this involved?) the object have no right to be naming said object. — Preceding unsigned comment added by MURODURUS (talkcontribs) 11:23, 18 November 2014‎