Talk:4 Vesta

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Contents 1 Anniversaries 2 Density 3 Rewrite 4 History 5 Diameters 6 Physical Characteristics 7 Fragments 8 GA 9 Symbols 10 Largest asteroid 11 Color image 12 Occasionally Ceres can come closer to the Sun than Vesta

[edit] Anniversaries

An event in this article is a March 29 selected anniversary (may be in HTML comment)

[edit] Density

Following [1] (Jan 9, 1998) the density of Vesta is only 3.9 ± 0.3 grams per cubic centimeter. Is this more recent/fiable than the current value of 3.3g/cm3?

Thomson et al. (1997) gives a mean radius of 258 km and Michalak (2000) a Mass of 1.36 ± 0.05 × 10–10 Sun masses. Based on this, Keil (2003) gives a density of 3.8 g/cm^3 -- Epo 10:44, 17 Mar 2004 (UTC)

The old density estimates of even 5.0 or so were based on the IRAS diameter which was far too small. Based on the newer HST data of Thomas [Science 277, p 1492, (1997)], the dimensions are 578x560x458 km ± 10 km, so a geometric average of 529 km, giving a volume of about 7.8±0.4×10¹⁶ m³. The latest mass estimate of Pitjeva (ref in article) gives about 2.67×10²⁰ kg, with maybe a 15% uncertainty by comparing to other people's results. This then gives a best estimate of density of 3.4 ± 0.5 (the uncertainty is kind of uncertain). Deuar 08:43, 13 November 2005 (UTC)

[edit] Rewrite

I reworked the whole article -- please somebody check the grammar since my Engrish is not perfect Jyril 21:27, 22 Jun 2004 (UTC)

After reading through a few papers on the topic, i've tried to put what i've gleaned into the article before I forget it or lose the notes ;-). The end result seems to have been a major reorganisation. Deuar 21:05, 13 November 2005 (UTC)

[edit] History

Needs some expansion on the discovery, and it's former status as a planet... The fact that it's visible to the naked eye seems like it only had bad luck not being picked as a classical planet. Tesseract501 March 23, 2006.

Needs some expansion on the discovery. Michaelbusch 18:08, 17 Aug 2006 (UTC)

Ceres is still the largest asteroid even though Ceres is also a 'dwarf planet'. Pluto is a Kuiper Belt Object (KBO) even though it is also a 'dwarf planet'.

[edit] Diameters

Regarding the Diameter: What does the third measurement (for irregular shapes) indicate? Am I correct to assume that the first measurement indicates the longest axis at the equator, and the second measurement the polar axis? If so, is the third measurement the secondary equatorial axis (at right angle form the longest equatorial axis)? Or is it the mean diameter or something else? Thanks ---- Tesseract501 March 23, 2006.

I believe it's standard for it to be at right angles to both. kwami 23:59, 23 March 2006 (UTC)

Thank Kwami. I checked out the info on several other planetoids. The values seem to indicate Triaxial Ellipsoid Dimensions (geometric measurements for irregular objects). From what I can tell, the three numbers only fall in order from longest to secondary to shortest diameter. Whether or not any of the three happen to be the equatorial or polar diameters may be uncertain. It gets even trickier because some asteroids may rotate in more than one direction (wobbling) because of their irregular shape and composition. So I don't know how someone could find that kind of data for the major known asteroids. I haven't found any sources to tell us what the equatorial(s) and polar(s) diameters are for specific asteroids. By the way, whoever put together the data on all the various asteroids did an AMAZING, SUPER JOB. It must be full-time work to keep them all updated. ---- Tesseract501 March 24, 2006.

A hunt for "most out of date solar system body" could be fun ;-) Deuar 16:55, 26 March 2006 (UTC)

For rotation to be stable over long timescales, the shortest DEEVE diameter must correspond to the axis of rotation and the two others are the major and minor axes of the ellipse formed by the DEEVE's intersection with the equatorial plane. Obviously, all three are at right angles to each other. Almost all objects in single-axis rotation, not tumbling (we can measure this by lightcurve and radar), so we can define the axes properly. 'DEEVE' stands for dynamically-equivalent equal-volume ellipsoid. It is an ellipsoid with equal volume and equal moments of inertia to a given asteroid. Such an object has the same mass, volume, and density as the target asteroid and is the standard for computing tri-axial ellipsoid dimensions. Michaelbusch 16:03, 17 August 2006 (UTC)

[edit] Physical Characteristics

Next to "Mean surface temperature", on the Physical Characteristics table, the min and max temperatures are given, the temperature Extremes for "4 Vesta", but not the actual "Mean surface temperature" for the asteroid. Obviously, the mean is easy to calculate, even for my little brain, from the min and max data but still there is an inconsistency in this table. Actually, I find the min max temperature more interesting data than just the mean by itself.

We cannot specify a mean temperature by taking the average of min and max, because we don't know the distribution of temperature across the surface of the asteroid. Even the min and max are uncertain, particularly the minimum (because we have little data on the nightside). We can calculate an average temperature for the surface by taking the albedo and average cross-section, using those to compute the total solar energy incident, then dividing that by the effective surface area of the object to get the mean power radiated per unit area. However, this is not the same as a geometric mean across the surface. Michaelbusch 16:03, 17 August 2006 (UTC)

[edit] Fragments

Could someone elaborate on how we know the meteorites originated on Vesta, and not some other asteroid? Gary 04:51, 20 August 2006 (UTC)

The spectra of the V-type asteroids, as well as the HED meteorites, match Vesta's very distinctive spectrum. The meteorites probably didn't come directly from Vesta, but we can assume that they have been through a similar history (see the physical properties section) Michaelbusch 16:20, 20 August 2006 (UTC)

• it is the same process as we know ALH84001 is from Mars. I just read about Vesta and those meteorites probably did originate in Vesta, Vesta was hit by a massive impact which destroyed part of it (that is why it is "half round, half not"). Vesta remains even reached Earth! So Vesta and Ceres are seen by leading planetologists as mini-planets and protoplanets, not as asteroids.-Pedro 22:25, 7 September 2006 (UTC)

[edit] GA

Good article, keep up the good work -- Nbound 00:54, 17 September 2006 (UTC)

[edit] Symbols

I've added a little more information, but I'm not sure where to link for MPC numbers. Please help! Adam Cuerden ^talk 23:52, 4 October 2006 (UTC)

...Weel, it was deleted. Still, it WAS accurate and cited, (and involved a fair bit of work to make the new symbol) so I paste the cut text here if anyone sees a better way to work it in. It starts just after the opening as it stands now.

When designated by a symbol it is usually , but it is sometimes or Image:100px-Simbolo di Vesta.jpg. All are simplifications of the original rather more detailed hearth, . The difficulty of drawing the symbols for the asteroids from Vesta onwards led to B. A. Gould suggesting a numbers in circles to be used instead, which would eventually simplify to the number in parentheses: (4) Vesta, and then finally to just the number: 4 Vesta - in short, the MPC number system used for all minor planets today. [2])

I thought it was fascinating. I'm not sure why it needed to go. --Aranae 02:27, 5 October 2006 (UTC)

My rational for the original deletion of the more detailed description of the history of the symbols was twofold: one that it was uncited (this has been fixed) and two that, while it is interesting, it was somewhat long and does not relate to the remainder of the article (because symbols are very rarely used, and almost never for asteroids). It might be appropriate in one of the articles dealing with the history of astronomical terminology. If there is consensus for keeping the material, let it be decided here. Michaelbusch 02:32, 5 October 2006 (UTC)

The only reason why I added the symbols to the body of the article was because I reduced the symbols at the top of the infobox down to just one, and some people complained about the same thing being done on 1 Ceres. Not only are asteroid symbols virtually unused in the astronomical world, but the astrological world pretty much only uses the one in the infobox. I'd cut it right down to "When designated by a symbol it is usually " if there weren't objections. _└ ^OzLawyer / _talk ^┐ 03:08, 5 October 2006 (UTC)

Er... actually, that cite was there from the start. Still, the main body of information probably ought to go in an article on Minor Planet Number - who wants to join me in writing one? Adam Cuerden ^talk 06:45, 5 October 2006 (UTC)

Er...actually, it wasn't. _└ ^OzLawyer / _talk ^┐ 12:36, 5 October 2006 (UTC)

It was, at least from when I added the controversial part. Not that it matters that much.

Yes, clearly it was there when you added to it. My point was that if I hadn't added it in the first place, the article might have continued without any discussion about the symbol, which I actually think is better. At the most, it needs just a note that the symbol at the top of the infobox is the most common of several symbols for the asteroid. _└ ^OzLawyer / _talk ^┐ 14:21, 5 October 2006 (UTC)

Sorry about that, got confused and was sttressing out a bit over an oral report at the time. Adam Cuerden ^talk 18:11, 5 October 2006 (UTC)

[edit] Largest asteroid

According to http://www.iau2006.org/mirror/www.iau.org/iau0603/iau0603_Q_A2.html , Ceres is no longer an asteroid. 132.205.44.128 05:15, 13 November 2006 (UTC)

I was the one who originally posted that reference... please see my reply to your post here. Thanks! --Ckatz^chat_spy 05:59, 13 November 2006 (UTC)

You can also see Talk Ceres and Talk kheider. I believe that Ceres is still an asteroid until an official statement is released. A poorly worded press release is not very reliable. Vesta may be a Dwarf Planet Remnant, and thus may not be an asteroid *IF* (1) the rule: "Once a dwarf planet, always a dwarf planet" is applied and (2) Dwarf Planets are not asteroids. -- Kheider 15:06, 13 November 2006 (UTC)

Sorry if my post wasn't clear... my link to "here" points to the discussion at Talk Ceres as well, since 132.205.44.128 posted a similar question there. --Ckatz^chat_spy 20:01, 13 November 2006 (UTC)

Actually that points to Talk Asteroid. So yes, the conversation is in multiple locations. :-) -- Kheider 19:36, 14 November 2006 (UTC)

Yes, well, I learned to read at a very early age, before all this new-fangled A-B-C stuff came about... 8) --Ckatz^chat_spy 21:32, 14 November 2006 (UTC)

[edit] Color image

A color image of Vesta is available:

http://hubblesite.org/newscenter/archive/releases/2007/27/image/c/

— RJH (talk) 21:37, 20 June 2007 (UTC)

As a Hubble image it's not PD. Is there a fair use rationale that applies? Lexicon (talk) 22:34, 20 June 2007 (UTC)

Please see http://hubblesite.org/copyright/ for Copyright information regarding hubble pics. Accroding to their copyright notice, this one is PD or FUR. Abyssoft 11:44, 21 June 2007 (UTC)

[edit] Occasionally Ceres can come closer to the Sun than Vesta

You can not allows easily diagram 3 dimensional space on a 2 dimensional drawing.

• For example look at the JPL orbital simulation for 887 Alinda. When you first load it, it looks like 887 Alinda crosses the orbit of Earth. But if you drag the bar on the right to the bottom, you will see that this asteroid does not cross Earth's orbit. Since it has a perihelion (closest distance to the Sun) of 1.07AU it does stay outside of the Earth's orbit.
• Another good example is Pluto. If you load the JPL orbital simulation for Pluto, zoom in some, and rotate to the left you can make it appear as if Pluto always stays further from the Sun than Neptune.
• If you look at JPL's 2-body orbital simulation for Ceres and Vesta and move forward to 2009-02-10, you will see that Ceres is closer to the Sun at that time. Vesta 2.56AU; Ceres 2.54AU. -- Kheider (talk) 17:03, 31 May 2008 (UTC)