Talk:2 Pallas

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Good article 2 Pallas has been listed as one of the Natural sciences good articles under the good article criteria. If you can improve it further, please do. If it no longer meets these criteria, you can delist it, or ask for a reassessment.
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[edit] Palladian

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

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] Planet

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

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

[edit] 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:

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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)