Talk:2 Pallas

Palladian

Per the OED, the adjectival form is Palladian (pa-lay'-dee-un). kwami 06:37, 2005 Jun 19 (UTC)

Photo

Was there originally a photo on this page? There appears to have been one at some point, because there's still a caption...--Firsfron 6 July 2005 02:49 (UTC)

Yes, there was a montage of the four largest asteroids, using the Ceres and Vesta images, and silhouettes for Pallas and Hygiea. But there was a copyright violation decided for the Ceres image, so it is now gone. I intend to redo the image some time... Urhixidur 2005 July 6 12:37 (UTC)

Can we use an image like: Shape of (2) Pallas (Source: shape model deduced from lightcurve) Kheider 18:31, 19 October 2006 (UTC)

We could, but that is not an actual image of the object (especially since the lightcurve modeling assumes uniform scattering). Another option is occulation chords, which show Pallas to be close to ellipsoidal at some epochs. Another option is for someone to go get an image. This would probably require lucky imaging, as time on Hubble or adaptive optics systems is hard to get. Even then, to make the observation would require a telescope in the 1-m regime (to get a meaningful number of pixels across the target). Any serious amateur astronomers reading this? There isn't too much interest on the professional side at the moment. Michaelbusch 18:43, 19 October 2006 (UTC)

Mass

Similarly to what I waffled on about in Talk:Ceres, discrepancies in mass estimates appear for Pallas as well as Ceres and Vesta, due to using different models/methods. The recent ones, apart from Hilton (which appears to be an aberration) hover between 1.0 and 1.2×10^-10 solar masses, so I've just taken the average of this, and referenced the two relatively recent papers which gave the most characteristic estimates. Deuar 21:45, 17 September 2005 (UTC)

Two unsupported claims?

This last edit made the claim that there are irregular TNOs larger than Pallas, giving 2003 EL61 as an example. However, we don't know that 2003 EL₆₁ is irregular, only that its lightcurve varies significantly. Unless there are other TNOs that are somehow known to be irregular, the "possibly" should be restored.

Also, the article claims that Pallas is irregular because its gravitational field never collapsed it into an obate [sic] spheroid. I don't know that that is true either: do we have evidence that Pallas is primordially irregular, rather than an originally spheroidal body with chunks knocked off it like Vesta? kwami 20:54, 11 October 2005 (UTC)

The 2003 EL61 article says that its huge elongation is "one posible explanation" of a strongly varying lightcurve, and a pretty exotic-sounding one to me. Albedo variations seem much more likely.

As for Pallas, well that looks like a good question. There is uncertainty about Vesta as well, although e.g. Thomas etal (Science 277 p1492) while reporting HST observations tended towards it being an equilibrium spheroid (its flattening is due to rotation as well as the south pole crater). Pallas is about the same size, but is less dense and has two short axes and one long (rather than two long ones and one short like Vesta), which makes it suspiciously like an irregular body. If its size is 570x525x500 you'd need two huge craters about 20km deep (comparable to the Vesta crater) on either side to reduce the second axis so much. That's possible, I guess, but seems unlikely. The major problem with Pallas, though, is that no one has taken good photos of it yet, and those diameters could be out by maybe 10-20km. So, um, I don't know, it seems a bit irregular. A paper Slyuta, Icarus Vol. 129, p. 401 (1997) claims it is irregular. Deuar 11:37, 13 November 2005 (UTC)

Irregularity

There were a few sentences in the article, and comments here, claiming that "Pallas is the largest irregular object in the solar system, with the possible exception KBOs such as 2003 EL61". EL61 is elongated, not irregular, so that comparion is meaningless. The available data suggests that Pallas is only marginally more irregular than Vesta, so the entire statement is meaningless. I therefore removed it. Michaelbusch 23:34, 25 August 2006 (UTC)

Sounds fair enough to me. I'm also wondering about the second deleted statement

Pallas is currently the largest Solar System body (barring trans-Neptunian objects) whose surface has not been directly imaged by spacecraft or telescopes.

Indeed, it's unreferenced as you point out. However, I am wondering whether we have any particular reason to doubt it − no resolved images of Pallas are published on the web or in scientific journals. Its just a fairly simple comparison with no in-depth research required. Imho it is desirable to mention it in the article because it is of interest to many general readers − it gives the asteroid some character as opposed to just another generic big rock. Unfortunately it is often difficult to find a reference for such things. Any ideas? Deuar 14:24, 28 August 2006 (UTC)

Second or third?

HST observations put Vesta at 578x560x458 km in size, while Pallas has a (rough) best estimate of 570x525x500 km. Older estimates tended to imply Vesta was the smaller. The present best size estimates are about the same, making it hard to decide who would be number two. However, Vesta is much more massive, which may make it the better candidate "overall" in some sense. Deuar 20:35, 11 November 2005 (UTC)

What, you don't think an average difference of 0.6% is rock solid? kwami 22:05, 11 November 2005 (UTC)

;-) Well, the paper where they give the Vesta dimensions [Thomas, Science 277 p 1492] gives uncertainty of 10 km (about 2%), and I believe it's even worse for Pallas. Deuar 11:33, 13 November 2005 (UTC)

Planet

Needs some expansion on the discovery, and it's former status as a planet...

Done Michaelbusch 23:34, 25 August 2006 (UTC)

Pole direction

Regarding the Celestial Lat and Long (RA and Dec), the text indicates that the pole points towards ecliptic coordinates (β, λ) = (-12°, 35°)... I am used to seeing the RA in hours, minutes, seconds, followed by the Declination in degrees. Is the text here indicating the Declination first? And then the RA (but in degrees instead of hours-minutes-seconds)? If so, is my assumption correct that Pallas' RA is 2 hours, 20 minutes (corresponding to the 35° reference)? I noticed this layout on other asteroids as well (e.g., 3 Juno), so I want to make sure of my interpretation. Others (1 Ceres, 4 Vesta, etc.) use the layout that I am more familiar with: RA hrs-min-sec followed by the Dec (degrees). Thanks for all this great info on the asteroid pages. Wonderful stuff.----Tesseract501, March 24, 2006.

Hi Tesseract! Another good point. I wonder where the inconsistency in notation among the asteroids arose from. To clarify things, there's two basic ways that we could specify the pole directions:

• ecliptic coordinates: with tilt angle to the ecliptic β called the ecliptic latitude. Both this and the ecliptic longitude λ seem to be usually specified in degrees.
• equatorial coordinates: with tilt angle to the Earth's equator (the declination). In this coord system right ascension "longitude" is specified in hours and minutes.

But which system to choose? Personally I prefer the ecliptic system because the ecliptic has some physical relevance for the asteroids, whereas the earth's orientation has none. Also, this site, which contains the most comprehensive up-to date pole data uses the ecliptic coordinates. However, the equatorial system is obviously more widely known. The conversion is actually nontrivial, and is given in the ecliptic coordinates article. Usually λ=α approximately. In this case α=2h28m, δ=+2° it turns out. I wonder whether I should update Ceres and Vesta to the more common coordinates.Deuar 18:28, 26 March 2006 (UTC)

Surely

Surely there is an image of pallas, gosh, It's the second most main asteroid, I'm going to find one -- Legolost EVIL, EVIL! 04:35, 4 September 2006 (UTC)

Not even 1!!! -- Legolost EVIL, EVIL! 04:44, 4 September 2006 (UTC)

Yeah, amazing, isn't it. Deuar 15:13, 4 September 2006 (UTC)

Was that carcastic? Shame we can't here voice on wikipedia -- Lego@lost EVIL, EVIL! | 04:09, 5 September 2006 (UTC)

Maybe a bit. I find it interesting that no resolved pictures of Pallas appear to have been taken. It's possible to do so because 4 Vesta and 1 Ceres have been imaged with several telescopes each, and Pallas is of a comparable size. Well, half the size of Ceres, and it never comes nearly as close to Earth as Vesta, but some resolution could still be had. However, it doesn't appear to be as exciting a body as Vesta and Ceres for various reasons, so I suppose astronomers haven't been able to win time yet on any of the several telescopes that can do the job. In any case, I'm waiting .... Deuar 12:19, 5 September 2006 (UTC)

Ephemeris?

An ephemeris ("aspects") of this asteroid was introduced by anonymous user 85.74.29.233 on July 7, 2005. Judging by the contributions, it looks like this user did the same for other asteroids. My feeling on this is that an ephemerides doesn't really belong in wikipedia. Since I can't find a suitable reference I'm thinking of removing it from this page. Does anybody have an objection to this, or a good alternative? Thank you. — RJH (talk) 15:41, 20 March 2007 (UTC)

Remove it. I've been wondering about this myself. We already have links to NEODys and JPL Horizons. Michaelbusch 17:00, 20 March 2007 (UTC)

Done. There's consensus on the "WikiProject:Astronomical Objects" talk page for this action as well. Thanks. — RJH (talk) 21:28, 20 March 2007 (UTC)

Link to Astronomical Objects talk page. -- Kheider 05:37, 20 September 2007 (UTC)

GA review

GA review (see here for criteria)

1. It is reasonably well written.

   a (prose): b (MoS):

2. It is factually accurate and verifiable.

   a (references): b (citations to reliable sources): c (OR):

3. It is broad in its coverage.

   a (major aspects): b (focused):

4. It follows the neutral point of view policy.

   a (fair representation): b (all significant views):

5. It is stable.

   

6. It contains images, where possible, to illustrate the topic.

   a (tagged and captioned): b lack of images (does not in itself exclude GA): c (non-free images have fair use rationales):

7. Overall:

   a Pass/Fail:

All in all, it's a good article and almost ready for GA status. A few specific comments:

• The article is a little jargony, but it's not too bad.
• It would be nice to have a higher res version of the image, perhaps an actual telescopic image. At the very least, it would be better if the displayed image didn't need to be resized larger than the original.
  • Yes it would. I'm hoping something better will become available at some point in the future.
• The source by Rincon cited about hydrostatic equilib doesn't actually say that it might be reclassified as a dwarf planet; rather, it says that under the (failed) IAU resolution, it would potentially become a planet. Try to find a source that has more up to date info.
  • That source is less than a year old. Unfortunately I couldn't find an online copy of the IAU's watchlist, which would be the most up-to-date source. I re-wrote it slightly.
• My most serious concern is an apparent factual error in the naming section. To wit, I believe the asteroid is actually named after Athena (thanks to her alternate name, Pallas Athena), not Pallas herself. The former is much more important mythological figure and would be a more likely candidate for an early planet name. Cf. Name_conflicts_of_solar_system_bodies#Conflicts_among_asteroids. Also a quick google reveals that astrologers commonly refer to it as "Pallas Athena asteroid" and this astrological source (not a reliable source on astronomy, but on mythology it might be ok) gives the history as being named after Athena. I tagged it with a {{fact}} Please find a citation one way or the other.
  • Done. — RJH (talk) 17:50, 29 March 2007 (UTC)

I'll put the nomination on hold until at least this last issue is resolved. --Flex (talk|contribs) 01:31, 29 March 2007 (UTC)

I made a few more superficial changes, but it looks good. If you find a better reference for the dwarf planet thing, that would be good, but I think it qualifies for GA status as it stands now. Congratulations! --Flex (talk|contribs) 18:48, 29 March 2007 (UTC)

Well hopefully the (to me trivial) subject of whether this is a "planet" or a "dwarf planet" will be cleared up with the passage of time and better observations. I didn't have great luck with that the first time I tried to reference the subject. Thank you for your review of this article. — RJH (talk) 22:22, 29 March 2007 (UTC)

Dwarf planet

As in the above section, I'd recommend you find a reliable source the describes exactly how 2 Pallas is classified. It seems that the rejected resolution asserts that it may not be in hydrostatic equilib, while the passed resolution (at bottom) gives the accepted definition of dwarf planet but doesn't mention Pallas. (The former also intimates that one may call dwarf planets "planets.") --Flex (talk|contribs) 19:29, 29 March 2007 (UTC)

I do consider BBC News a reliable source. If this remains an issue then I'd just as soon see that "planet" stuff ripped out of the article because, to me at least, it's the least important aspect of the subject matter. It's also taking up way too much of the introduction than it deserves. So I'm more than happy to use this as an excuse to remove it completely, as I don't want to waste another 4 hours looking for better references on this inconsequential sub-topic. Thanks. — RJH (talk) 21:51, 29 March 2007 (UTC)

Not that it matters to this discussion, but I decided to move the "planet" topic down into the body and replace it with more introductory information. — RJH (talk) 22:20, 29 March 2007 (UTC)

I agree with the move. The statement probably didn't belong in the lead.

To my knowledge, there has been no revisiting of the Pallas issue since the redefinition of planet in 2006. I doubt that a better source is available. I think the fact that Pallas made the list of candidate planets in the early draft is notable enough to make it into the article and is a verifiable statement. Whether Pallas has the potential to be listed as a dwarf planet is a bit more troublesome, due to a lack of any sort of discussion of the matter since the term "dwarf planet" was defined. This statement is the result of an "if A=B and B=C then A=C" logic. Pallas was a candidate planet according to the proposed definition of planet (verifiable). The current definition of dwarf planet is identical to the proposed definition of planet except for the issue of neighborhood clearing (verifiable). Therefore Pallas has the potential to be classified as a dwarf planet. I personally think that this type of logic is sound and do not consider it to be original research, but I may hold the minority opinion here and don't object to the deletion of the offending remark. Again, I do think its brief 2006 status as a potential planet should stay.

Prior to my change, the wording of the section was: "In the future, it is possible that Pallas may again be classified as a planet (specifically, a dwarf planet under the current IAU classification scheme), but only if it is found that its shape is consistent with hydrostatic equilibrium." I object to two aspects of this statement. The first is the implication that dwarf planet is a subcategory of planet. There is nothing in the final resolution that suggests that dwarf planets are types of planets and the going interpretation is that the two are mutually exclusive categories (see Talk:Dwarf planet or the many archives in Talk:Pluto). My second objection relates to the first in that there really is no chance that Pallas will be considered a planet, though there is a chance that it will one day be considered a dwarf planet. This earlier wording is no better at dealing with the potential of OR than the later wording; the train of A, B, and C logic is there in this statement as well as the changed statement. --Aranae 02:19, 30 March 2007 (UTC)

I don't think its dwarf status is inconsequential information. The fact that it may someday be reclassified as a dwarf planet establishes it as one of the more important smaller bodies in the solar system.

Also I agree the BBC is a reliable source, but my point was that that article only talks about Pallas in terms of the failed IUA resolution, under which it would have potentially been termed a full-fledged planet. I'd just like to see something that discusses it explicitly in terms of the resolution that actually passed. --Flex (talk|contribs) 02:27, 30 March 2007 (UTC)

We talked about this problem back when the dwarf planet article was getting started. It's quite frustrating from a wikipedia perspective to not be able to cite anything but pre-resolution speculation concerning the status of these objects. It seems that everyone was excited at the concept of many new planets, but no one really cares about all the potentials now that they're lowly dwarf planets. Here are a couple of sites, none ideal, that do list Pallas along with other projections: [1], [2], [3] --Aranae 04:59, 30 March 2007 (UTC)

To me the argument about whether the name "dwarf planet" applies to 2 Pallas seems to be purely semantics. That doesn't change the characteristics of the body; only our nomenclature categorization. It would be interesting to know, however, how close 2 Pallas is to hydrostatic equilibrium, as that might (slightly) improve our understanding of the Solar System's formation. — RJH (talk) 16:24, 31 March 2007 (UTC)

Exactly. I keep being surprised that there's been no high resolution images made of it. Bummer. Deuar 12:42, 2 April 2007 (UTC)

The "high" resolution images of Ceres required time on the HST, which is difficult to obtain with all the other priorities. Also the ACS on Hubble just broke, so (if they haven't got any images in the pipe) we may not be seeing any more such pictures for up to a decade or so. That'd be my guess, anyway. — RJH (talk) 22:22, 2 April 2007 (UTC)

The WFPC2 camera is still operating, and will be replaced by WFPC3 during the next Hubble servicing mission in 2008. If it is determined that the ACS can be fixed it may again become operational. Ground-based telescopes equipped with adaptive optics (especially the Keck telescopes) are capable to image the largest asteroids in better resolution than Hubble.--JyriL ^talk 10:10, 3 April 2007 (UTC)

Great. I wouldn't expect that imaging 2 Pallas is high on their priority list though. — RJH (talk) 19:22, 9 May 2007 (UTC)

It looks like Hubble observations of Pallas may have been planned for September 3, 2007.[4] — RJH (talk) 15:45, 7 November 2007 (UTC)

Visit by Dawn mission

With regards to a visit by the Dawn mission, rumor has it that Pallas will cross the descending node in December, 2018 (but we'd need an accurate ephemeris to check). So it will be crossing the orbital plane of Ceres and a fly-by mission may be conceivable. Dawn just wouldn't have the fuel to enter into orbit. — RJH (talk) 15:43, 7 November 2007 (UTC)

This point may need some clarity in the article, as both ideas (that a visit is possible, and that it isn't) are given.

Erwins feline (talk) 18:21, 1 March 2008 (UTC)Erwin's Feline

I'm not sure I understand the source of the confusion. The text states that an orbit can not be achieved but that a fly-by is possible. Why is this unclear?—RJH (talk) 18:00, 2 March 2008 (UTC)

Another way to put it: Dawn might have enough fuel to leave Ceres on a trajectory for Pallas, but once it nears Pallas it would not have enough fuel for proper orbit insertion. -- Kheider (talk) 19:33, 2 March 2008 (UTC)

Obliquity

Using orbit pole coordinates (β, λ) = (55°, 83°), I calculate respective obliquities of 78° or 65° for the rotational poles having ecliptic coordinates (β, λ) = (-12°, 35°) or (43°, 193°) instead of 57° or 65°, respectively. Bassesq (talk) 23:43, 3 February 2008 (UTC)

Possibly this needs to be addressed to the authors of:

J. Torppa et al (1996). "Shapes and rotational properties of thirty asteroids from photometric data". Icarus 164 (2): 346-383.

Perhaps they made some sort of correction? Thanks.—RJH (talk) 20:41, 4 February 2008 (UTC)

J. Torppa et al (1996) is (2003). They did not include any calculation of Pallas's obliquity in their paper, just the two solutions for its pole. No reference for the 57° or 65° is provided. Bassesq (talk) 03:25, 11 February 2008 (UTC)

I added a {{Fact}} template to the sentence. Thanks for pointing it out.—RJH (talk) 22:35, 12 February 2008 (UTC)

GA Reassessment

This discussion is transcluded from Talk:2 Pallas/GA1. The edit link for this section can be used to add comments to the reassessment.

This article has been reviewed as part of Wikipedia:WikiProject Good articles/Project quality task force in an effort to ensure all listed Good articles continue to meet the Good article criteria. In reviewing the article, I have found there are some minor issues that may need to be addressed.

• In the lead section, the sentence "It was the second asteroid to be discovered, found and named by astronomer Heinrich Wilhelm Matthäus Olbers on March 28, 1802." This seems to imply that it was the second asteroid discovered by Olbers on March 28, 1802, which is not the case. I recommend splitting this into separate sentences.
  • Note: I split this up by adding the date of discovery to the first sentence. GaryColemanFan (talk) 20:13, 16 August 2008 (UTC)

It now has my wording, which gives more emphasis to the order of discovery. Revert if you prefer. kwami (talk) 20:22, 16 August 2008 (UTC)

Actually, I prefer your wording. GaryColemanFan (talk) 15:45, 17 August 2008 (UTC)

• The first paragraph of the "History of observation" section is unreferenced.

Done. kwami (talk) 20:39, 16 August 2008 (UTC)

• In the same section, I believe that the parenthetical statement "(Members have semi-major axis = 2.50–2.82 AU; inclination = 33–38°.)" should come before the period in the previous sentence.

I disagree. They are two independent sentences. kwami (talk) 20:22, 16 August 2008 (UTC)

I merged the sentences while trying to make it clear that the second part does not infer the first.—RJH (talk) 19:15, 18 August 2008 (UTC)

• In the first sentence of the "Characteristics" section, I find the statement "(to within uncertainty)" confusing. Could you explain what this means?

Done, though I made it a footnote as that's probably best when trying to explain precise terminology in imprecise terms. kwami (talk) 20:22, 16 August 2008 (UTC)

• There is a "citation needed" tag in the "Characteristics" section.

Those numbers seem to be inconsistent, but I don't know how to verify them. kwami (talk) 20:54, 16 August 2008 (UTC)

Another editor has helped out, so this is good now. GaryColemanFan (talk) 15:45, 17 August 2008 (UTC)

• Reference 13 does not appear to be a reliable source. Although it says that it was based on the 1911 Encylopaedia Brittanica, anyone can edit it.
  • Note: I removed the reference, as there was another, more reliable reference already listed. GaryColemanFan (talk)
  • Meanwhile I'd redirected to a scan of the original EB. kwami (talk) 20:22, 16 August 2008 (UTC)
• Reference 23 is missing a publisher.

Done. kwami (talk) 20:22, 16 August 2008 (UTC)

• Reference 23 is a dead link.

Fixed. kwami (talk) 20:22, 16 August 2008 (UTC)

• I recommend alphabetizing the "External links" section.
  • Note: I alphabetized it. If there was a reason for the different order, feel free to change it back. GaryColemanFan (talk) 20:11, 16 August 2008 (UTC)
  • That's fine. I did the same. kwami (talk) 20:22, 16 August 2008 (UTC)

Edit conflict: did much of the above, but got reverted. Following up. kwami (talk) 20:15, 16 August 2008 (UTC)

Sorry about that. I was trying to take care of some of the smaller things. I'm finished editing for now. GaryColemanFan (talk) 20:19, 16 August 2008 (UTC)

I am placing the reassessment on hold for one week to allow for these changes to be made and/or discussed. If work is still being done at the end of the week, the hold can be extended. Please get in touch here or on my talk page if you have any questions. Best wishes, GaryColemanFan (talk) 19:31, 16 August 2008 (UTC)

I'm satisfied with the condition of the article. I don't agree that a parenthetical sentence can stand on its own, but this isn't a big enough concern to hold up the review. I'm closing this as a keep, and I encourage the editors to keep adding to it and touching it up as new information becomes available. GaryColemanFan (talk) 15:45, 17 August 2008 (UTC)

Well then what has to be done to make this a Good Article? --IdLoveOne (talk) 03:40, 21 November 2008 (UTC)

axial tilt

There was an unref'd conversion of the ecliptic coordinates of the pole to axial tilt, and under GA review this was deleted. Can anyone do the conversion, so that we know what the most recent solutions represent in layman's terms? kwami (talk) 20:18, 17 August 2008 (UTC)

The coordinates of the orbital north pole are necessary for this caclulations. From the known inclination (34.8°) and longitude of the ascending node (173.2°) they are:

$\beta '=55.2^{o},\quad \lambda '=83.2^{o}$

Now the axial tilt ε is

$\cos \varepsilon =\cos \beta \cos \beta '\cos(\lambda -\lambda ')+\sin \beta \sin \beta ',$

where λ and β are rotational pole coordinates.

My calulations showed that

$\varepsilon _{1}=78.4^{o},\quad \varepsilon _{2}=65.3^{o}$

for two possible pole positions, respectively.

Ruslik (talk) 11:49, 19 August 2008 (UTC)

Thanks, Ruslik. This is the tilt relative to Pallas' own orbital plane, correct?

I'm confused. Where are you getting α, since we're only given β and λ? kwami (talk) 22:34, 19 August 2008 (UTC)

Sorry, I meant λ (I corrected formulas). The tilt is relative the orbital plane. Ruslik (talk) 08:38, 20 August 2008 (UTC)

Okay. I was wondering if that could be it, as your ε2 looked way too close to ε1. I get 78±13° and 65±12° (simply plugging in the error ranges and taking the max divergence to be the error in tilt, so it might be better to make a more sophisticated error analysis). kwami (talk) 09:25, 20 August 2008 (UTC)

Wouldn't this mean the rotation is prograde? Or does "pole" not necessarily mean "north pole"? kwami (talk) 09:30, 20 August 2008 (UTC)

Since ε<90°, the rotation is prograde. Ruslik (talk) 10:02, 20 August 2008 (UTC)

I agree—the second value is 65°. Ruslik (talk) 10:06, 20 August 2008 (UTC)

Yeah, I'd think that it meant the rotation is prograde, but the data is from 2003, and at the beginning of the paragraph we state, "As of July 2008 a consensus has not been reached as to whether Pallas' rotation is prograde or retrograde." kwami (talk) 17:19, 20 August 2008 (UTC)

Gravity

Given the new size estimates from the Hubble images, perhaps we should recalculate the surface gravity & escape velocity. kwami (talk) 10:51, 24 August 2008 (UTC)

I think if we do that, then there should at least be a citation for the formulae used. Thanks.—RJH (talk) 18:45, 16 September 2008 (UTC)

The formulas are at the links, but in any case the new data don't make any significant difference. Still 0.32 at the longest axis. kwami (talk) 19:43, 16 September 2008 (UTC)

What is the point of "Transits of Planets" section?

As I was visiting this site, I read the above section and my immediate response was "and WHO CARES...?" With a (journeyman level) background in astronomy, it is somewhat obvious to me that you would be able to see solar transits of the inner planets from Pallas - IF YOU LIVED THERE. However I am wondering why this information is 1) listed at all and 2) with such detail that someone actually entered the transit years for the planets as if this trivial information wasn't already esoteria to the nth degree to begin with. The linked page says zero about transits, Pallas, or anything else beyond how the program works. I have found this identical info on other asteroid sites (such as Ceres), so it appears to be a systematic edit - although oddly started. Therefore my suggestion is that this section be deleted as trivia and as a somewhat obvious advertisement. Ckruschke (talk) 14:07, 21 March 2011 (UTC)Ckruschke

Please keep the conversation in one place. See: Talk:Ceres (dwarf planet) -- Kheider (talk) 17:18, 21 March 2011 (UTC)

Some people seem to find this type of information interesting. I agree they are likely in a minority.—RJH (talk) 22:09, 22 March 2011 (UTC)

Shape

In the lede it is claimed that Pallas appears the largest irregularly shaped body in the Solar System. This is not supported by any citation. A while ago I removed the only 'citation' for this because it didn't actually claim Pallas to be irregular. Also, given the low resolution of the best images we have and that its maximum and minimum dimensions differ significantly less than those of Vesta (which is regularly claimed to be regular), I suspect that it cannot be said with such certainty. Thoughts? --JorisvS (talk) 14:03, 1 September 2011 (UTC)

Maybe a "may be" or "one of the" since we can't be sure. I don't think anyone still proposes that Pallas may be a DP, so the question is whether Vesta is both not a DP and larger than Pallas, and whether there are any rocky irregular TNOs out there which are larger, though per Brown the latter option would seem to be unlikely. — kwami (talk) 14:25, 1 September 2011 (UTC)

A "may be" or "possibly" would be much better, yes. Let's break down the issue I laid down:

• Vesta is suspected to have achieved equilibrium only to have it disrupted by a massive impact: What does this mean for DP status?
• Could something comparable have happened to Pallas? (Pallas' dimensions differ less than those of Vesta, 582×556×500 vs. 578×560×458)
  • And could they tell the difference?

Of course we can answer these questions only by referring to RSs. What can we find about these? If there is no one who still proposes that Pallas may be a DP, then the reasons for this would be quite interesting and there should probably be an RS out there saying it is not in equilibrium. --JorisvS (talk) 15:39, 1 September 2011 (UTC)

AFAIK, Pallas is fairly irregular all over. Vesta is an ellipsoid apart from the massive southern crater. So maybe it's an ex-DP, but that wouldn't apply to Pallas. Mars has an even larger crater (the northern hemisphere), though of course it rebounded to equilibrium, which Vesta did not. (I wonder, though, if Mars would rebound today? If not, how would we classify it if were hit by s.t. like that again?) It's not just a matter of size: Vesta is denser than Pallas, and that means more radioactive when it was formed, which means a warmer history, and equilibrium is easier at higher temperatures. — kwami (talk) 18:03, 1 September 2011 (UTC)

Aside: Yes, Mars would rebound. It's not just observational, there are several papers that calculate the size at which roundness happens. Eventually, the pressure is great enough to crush the structural material (ice or rock) even without any radiation heating or external effects (e.g., tides). The theoretical threshold for solid, pure silicate bodies (like, presumably, Pallas or Vesta) is around 600 km. It's around 320 km for ice. Even Mercury is way past that. Tbayboy (talk) 03:25, 2 September 2011 (UTC)

Thanks. Could you point me to (some of) these papers? --JorisvS (talk) 12:46, 2 September 2011 (UTC)

Lineweaver & Norman and Cole that I remember and can find. I believe Cole is extracted from a book he published in the 80s, but I don't have the reference to hand. Tbayboy (talk) 15:35, 2 September 2011 (UTC)

The 2009 Science article says in the abstract that "Pallas's shape is an ellipsoid with radii of 291 (+/-9), 278 (+/-9), and 250 (+/-9) kilometers". Ellipsoid for modeling, that is: an equilibrium object wouldn't be scalene unless it were rotating quite rapidly. I don't think 8 hrs is gonna do it: Ceres is 9 hrs, and Haumea is 20× as massive and rotating twice as fast.

"Pallas is big enough and round enough that it's very possible that its interior started to separate out," Ms Schmidt told BBC News. "Ceres is perfectly round and so there's a really good chance that that happened. For Pallas, it may be just that this process got started but never finished."

Also, what about our physical parameters? The density of ≈2.8 is dated to the 2008 paper, but disagrees with the 2009 Science article by the same authors, which give the same size but a density of 2.40±0.25. Have we recalculated the density and failed to replace the ref? — kwami (talk) 18:21, 1 September 2011 (UTC)

There's also a new article: Carry, B., et al. (2010) (2010). Physical properties of (2) Pallas. Icarus 205 (2): 460-472, where a 3.4 density value is reported. --Harlock81 (talk) 21:19, 15 September 2011 (UTC)

High inclination

Does anyone know of any hypotheses about why Pallas has such a high-inclination orbit? --JorisvS (talk) 18:22, 12 September 2011 (UTC)

I would guess that Pallas helped eject (or caused to collide with a 3rd object) another protoplanet in a gravitational dominance fight while the asteroid belt was trying to accrete. It is common for gravitational interactions to cause eccentricity to be exchanged for inclination and vice-versa. -- Kheider (talk) 15:41, 12 September 2015 (UTC)

The Kozai mechanism? Then I calculate that it could have had eccentricity up to 0.59, giving an aphelion of 4.4 AU, easily within the current influence of Jupiter. So could Jupiter have caused it? --JorisvS (talk) 16:01, 12 September 2015 (UTC)

I would not be surprised if Jupiter was involved in helping create Pallas' inclination when Jupiter was migrating. Jupiter has so many footprints in the asteroid belt. The big question is how many protoplanets where in the asteroid belt when Jupiter first formed? -- Kheider (talk) 16:52, 12 September 2015 (UTC)

There could have been a great many and no way to answer that question, especially if Jupiter indeed plunged into the inner Solar System before being pulled back where it is now. --JorisvS (talk) 21:49, 12 September 2015 (UTC)

Temperatures

Hi, I'm looking for a source for temperature data present in the article. Yesterday I found that Johnston at al. may be a good source for the mean temperature value. Johnston at al. (p. 1598) indeed furnishes 165 K as the equilibrium temperature value for a rapid rotating body at the mean distance of 2 Pallas from the Sun. However, I haven't found any source for the maximum temperature value. Do you have any? Thanks. --Harlock81 (talk) 21:16, 15 September 2011 (UTC)

• Johnston, K. J.; Seidelmann, P. K.; Wade, C. M., Observations of 1 Ceres and 2 Pallas at centimeter wavelengths Astronomical Journal, vol. 87, Nov. 1982, p. 1593-1599

Dwarf planet?

Put bluntly, it is misleading to suggest Pallas is a dwarf planet. -- Kheider (talk) 06:10, 12 September 2015 (UTC)

Yes. See the 2010 Carry paper that Harlock81 posted here above. Tbayboy (talk) 14:50, 12 September 2015 (UTC)

Candidate dp?

You will need a reliable and recent source to claim Pallas is still an accepted dp candidate. Looking at Vesta and Ceres, I do not see how anyone can still expect less massive Pallas to make the dp cut. Resembling a sphere does not make an asteroid a dp. -- Kheider (talk) 23:08, 2 October 2015 (UTC)

Vesta got hit in its south polar basin in a catastrophic event. Ceres didn't, and we see from light curve models that Pallas probably didn't either. It appears Pallas is slightly elongated, but nowhere near as much as Vesta. Rock collapses into a sphere around 500 km in diameter - Pallas is right at 550km in one side, and averages out to 512 km. It is also VERY close, if not in, HE:

https://books.google.com/books?id=3NLLj8hQHXoC

Page 4 says that Pallas is close to HE, and says the same for Ceres. There's a recent source. It's a 50/50 chance that Pallas is in HE, considering that not all asteroids that COULD be hit were hit. DN-boards1 (talk) 23:19, 2 October 2015 (UTC)

Michael W. Busch (2010) says "For the largest asteroids - Ceres, Pallas, Vesta, Hygiea - gravity dominates over material strength and their shapes are relatively close to HE." But at no point does page 4 state that "Pallas, Vesta, or Hygiea" are dp candidates. -- Kheider (talk) 23:35, 2 October 2015 (UTC)

It says they're close to HE. Pallas is closer to HE than Vesta and Hygiea, for starters. DN-boards1 (talk) 23:39, 2 October 2015 (UTC)

And the only two closer to HE than Pallas are Ceres and Interamnia.

Interamnia's article states that it has "fully withstood all impacts". It's done a better job of staying intact than Vesta, is in an ellipsoidal shape, is big enough, and lightcurve data for it suggests a spherical object. So we're left with Interamnia and Pallas, having discarded Vesta (known to be out-of-round), Hygiea (also out-of-round), and Cybele (yet again, out-of-round).

Wait, wait, wait.

This exists? http://arxiv.org/PS_cache/arxiv/pdf/0912/0912.3626v1.pdf

Why were none of the images from it in the article? Where did they get "irregular shape" from? That looks like an ellipsoid! DN-boards1 (talk) 23:23, 2 October 2015 (UTC)

Rock generally collapse into hydrostatic equilibrium closer to 800km. Sphere-like simply is not good enough. And Wikipedia does not allow Synthesis of published material.-- Kheider (talk) 23:41, 2 October 2015 (UTC)

If sphere-like is not good enough, then why is Haumea a DP? DN-boards1 (talk) 23:45, 2 October 2015 (UTC)

Also, these debates over Pallas being a DP are probably good material for Wikipedia:Lamest edit wars, actually. DN-boards1 (talk) 23:48, 2 October 2015 (UTC)

No worse than the "Is Pluto a planet?" debate. Physically, it does not matter what we call Pluto. -- Kheider (talk) 16:05, 3 October 2015 (UTC)

Haumea is largely made of ices while Pallas is largely made of rock. An object needs to be in HE and shape is just a product of HE. -- Kheider (talk) 23:52, 2 October 2015 (UTC)

Haumea is actually mostly rock. And given that icy Iapetus is not technically in hydrostatic equilibrium, we have no reason to really to think to know that Haumea and Makemake are actually in hydrostatic equilibrium. They'll be round, though. I don't know if Dawn's measurements have been sufficient to confirm/disconfirm hydrostatic equilibrium for Ceres. --JorisvS (talk) 11:15, 3 October 2015 (UTC)

Haumea may have a rocky core, but given the high albedo it has ices on the surface. Pallas does not have ices on the surface. So I will not be too surprised to find Pallas has a higher bulk density. -- Kheider (talk) 16:05, 3 October 2015 (UTC)

Page 7 (section 4.3) opens, "we found Pallas to be an irregular asteroid with significant departures from an ellipsoid" -- Kheider (talk) 23:52, 2 October 2015 (UTC)

Can we add images from that to Commons and then add them to the article? I get it now, if I had known about this paper this would have never happened. And now, we move to the Interamnia talk page to discuss it. DN-boards1 (talk) 23:57, 2 October 2015 (UTC)

Density

AFAIK, the infobox now has the best size and mass estimates available. The density I calculate from this is 3.0±0.5 kg/dm³. However, the article with the mass estimate uses an older, less precise size estimate to calculate the density, and the article with the size estimate uses an older, less precise mass estimate to calculate the density, so that neither has this value. It is a rather simple calculation, but it does feel like WP:SYNTH to me. Yet, if we don't, we unavoidably end up listing a density inconsistent with the listed size and mass (or using a less precise size or mass than is currently available). What should we do? --JorisvS (talk) 13:30, 13 September 2015 (UTC)

The volume and surface area are also calculated (surface gravity and escape velocity, too?). It isn't the number crunching that's a synth problem, but the choices of the formula and inputs. For example, here you could calculate the density by adjusting Carry's numbers for the new mass, rather than use the calculated ellipsoidal volume, since Carry might have used a more complicated potato-shape model (does the paper say?). That is, Carry's-density times correct-mass divided by Carry's-mass. Another way is to use the page's volume and mass, which better preserves page consistency. I guess you could also get volume from Carry's numbers and display that on the page, but it might be hard because of the error bars. If they all come to near the same number (that is, lost in the round-off), then all is well, but otherwise there's a synthy choice to make. I think this calculation is okay here, so long as it's noted, maybe with multiple entries from the sources to illustrate why the calculation was necessary. Tbayboy (talk) 14:27, 13 September 2015 (UTC)

If mass and volume are given, an these values are neither derived from each other, nor based on any presumed density, then the density is unavoidably the quotient of both, no? So my question is: is there ever any volume, mass or density assumed to derive mass or volume? If not, how can it possibly be original research? (PS: I don't know sh*t, so plz indulge me) -- Rfassbind – talk 15:11, 13 September 2015 (UTC)

The volume in the infobox is not from the source, but was calculated from the tri-axial dimensions given by the source, which in turn is a best-fit approximation to their physical model. It might be the volume used by the source (Carry) in their density calculation, but they appear to have developed a more detailed model of Pallas's shape and may have used a more accurate volume calculation. That said, I would guess that any difference between the tri-axial volume and the hypothetical model's volume would fall within the round-off by the time we get to density, because Pallas doesn't seem too potato-y. Most larger bodies are approximated by tri-axial dimensions, unless you're trying to land on them or do a close orbit. I don't have any objection to using the tri-axial dimensions (just note it), but I'm pointing out a possible synth/OR issue. Tbayboy (talk) 16:46, 13 September 2015 (UTC)

Gee, I should have noticed that. Obviously figures don't match at all: the source used for the mean density uses an older and much higher mass estimate (about 70% more than in the article) and still ends up with density of 2,762 kg/m³ which is lower than JorisvS's figure above. There's just too much error for me. I'll be quiet now and leave it to the big boys. -- Thanks for the help, Rfassbind – talk 21:08, 13 September 2015 (UTC)

Yes, the density is simply mass divided by volume, by definition. The density currently listed is from before I updated Pallas's dimensions with a newer source. The currently listed density's source uses a significantly larger size to calculate it, which is therefore lower. --JorisvS (talk) 10:44, 14 September 2015 (UTC)

@Tbayboy: The article does not say explicitly whether they used a potato shape in their calculations. They do list a volume, though, 7.0±0.3 km³, which is simply the volume calculated from the mean radius assuming a sphere, and hence less accurate than the value we list. Using their volume gives a density of 3.4±1.0 kg/dm³. However, using their mass and an ellipsoidal shape does not significantly affect the density estimate. Note that using their figures, I arrive consistently at an uncertainty of ±1.0 kg/dm³, not ±0.9 kg/dm³, though.

The mass used in Carry2009 comes from Michalak2000, whose estimate was made from the average mass as derived from deflection angles of two bodies, whereas Baer2008's estimate is from the average mass as derived from the deflection angles of four bodies, which can hence be expected to be more accurate. This really comes down to making a choice: Using the best estimates for the size, shape, and mass available (which are currently listed in the infobox) and accept simply calculating the (consequently more accurate) density from these, even though this density is not listed in either source, or accept using a not-the-best-possible estimate for either its mass or dimensions. --JorisvS (talk) 10:44, 14 September 2015 (UTC)

I think we should choose the former. This is the only way to have the best possible values in the infobox. --JorisvS (talk) 15:31, 17 September 2015 (UTC)

Agreed. Especially on this page, since mass/volume (211/71) is easy to do in your head and see that it should be very close to 3; 2.8 sticks out as something being obviously wrong. There's a similar problem on Makemake with size-H-albedo, but nobody's likely to see that. Tbayboy (talk) 23:34, 17 September 2015 (UTC)

Infobox background color

All articles about minor planets use the template {{Infobox planet}} which has an optional "background" (or bgcolour) parameter to set a bgcolor for the subheadings or section titles within the infobx. In most cases, this   is the standard color, while   2 Pallas and   4 Vesta have different ones. I also encountered some articles with another or no background color at all. (PS: comets using the {{Infobox Comet}} template use a hardcoded, yellow background (e.g. 81P/Wild), while several others, such as Tempel 1 and 67P/Churyumov–Gerasimenko use the {{Infobox planet}} template instead and without any defined color for the subheadings).

Question: Is there a concept behind the choice for these colors (and the different templates used for comets)? If not, wouldn't it be a good idea to define a consistent color scheme that corresponds to a given classification? For example: main-belt asteroids, dwarf planets (and candidates) KBOs, comets, centaurs, trojans, NEOs. For such a color-classification scheme, a few simple rules would suffice to resolve any ambiguity. -- Cheers, Rfassbind – talk 14:19, 13 September 2015 (UTC)

I don't think there is anything consistent. Good idea to set up such a scheme. --JorisvS (talk) 15:29, 17 September 2015 (UTC)

Thx for the reply. Here's a draft. What do you think? -- Rfassbind – talk 00:01, 18 September 2015 (UTC)

Asteroids (default)     Centaurs   Hildas   Trojans   Comets   NEAs   PHAs

TNOs (default)     Dwarf planets   SDOs, DDOs

Planets (no color)   Moons

I think it would be a good idea to continue this discussion at more relevant, centralized place, don't you? --JorisvS (talk) 09:03, 18 September 2015 (UTC)

Moved to WT:Wikipedia talk:WikiProject Astronomy

Higher quality images

Can we get some of the images from that paper on Pallas's properties uploaded and into the infobox? They are FAR more useful than that grainy Hubble image. DN-boards1 (talk) 17:57, 3 October 2015 (UTC)

I hope so, but we should check whether they are in the public domain first. --JorisvS (talk) 00:01, 4 October 2015 (UTC)

I agree on checking for public domain. DN-boards1 (talk) 00:09, 4 October 2015 (UTC)

Metric measurements

I'm an educated person, with advanced degrees though not in the sciences or mathematics.

The use of metric measurements without imperial (U S.) measurements makes this article utterly incomprehensible and almost utterly meaningless.

Such articles should all provide equivalents in a system that 315 million potential American readers might read, and I'm not particularly inclined to resort to opening a Google page in another window to constantly have to go back and forth between this and that just to be able to read what SHOULD be CLEARLY written in an article that any reader of English can comprehend.

That is, if Wikipedia wants to be taken the slightest bit seriously as being minimallyinformational by most of the population of North America. 2600:1700:4FD0:5AD0:AC91:CC5B:8FE1:69D2 (talk) 07:23, 13 December 2021 (UTC)

How would they make more sense in Imperial? What would you compare them to? Only other astronomy articles, which use the same measurements. For anything else, just read a km as a mile and a kg as a pound, and you're close enough. — kwami (talk) 07:44, 13 December 2021 (UTC)

I am an American. All a person needs to know is that 80MPH is roughly 120KPH. In other-words the 2/3rds rule gets you close enough without cluttering the article/infobox with too many conversions. -- Kheider (talk) 08:49, 13 December 2021 (UTC)