Talk:2 Pallas

From Wikipedia, the free encyclopedia

You have new messages (last change).

Contents

[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)
Retrieved from "http://en.wikipedia.org../../../2/_/p/Talk%7E2_Pallas_f80b.html"