Talk:2002 AA29

What does this illustration show? Certainly doesn't look like a horseshoe. And it seems to show the asteroid circling Earth hundreds of times per year, not coming close once every 95 years. What are we looking at in the picture? Rmhermen 14:58, Sep 3, 2004 (UTC)

Although I'm not the author of this article (I'm the author of the german article of 2002 AA29: de:2002 AA29) I know what this image shows. It shows 2002 AA29 in quasi-satellite-orbit not in horseshoe-orbit. And yes it takes exactly one year for each loop as shown in the picture, because it is not a normal orbit around earth like the one from the moon. Currently 2002 AA29 is in a horseshoe orbit. It is a unique feature of this asteroid that it can switch between those two orbits (next time in about 600 years). Further information in english about those strange orbits (and the source of the image) can be found at http://www.astro.uwo.ca/~wiegert/AA29/AA29.html

I have also some further questions to the author of the article: Where did you take the physical parameters (as mass and density e.g.) of 2002 AA29 from? Beside the orbital parameters the only physical parameters I could find were the diameter and the absolute magnitude (http://earn.dlr.de/nea/K02A29A.htm and http://www.jpl.nasa.gov/releases/2003/1.cfm). Did you assume a value for density and then computed mass and gravity? Greetings, Arnomane (in german wikipedia)

Yes, as the question mark shows, I assumed a default density of 2; this then allows mass, gravity and escape velocity to be computed. You may want to fetch my AstOrb Browser application to see how easy this makes wiki entries. If there is a de.wikipedia template similar to the English (Template:Minor Planet) or the French (fr:Modèle:Planète mineure), I could easily add it to the application.

Urhixidur 23:47, 2004 Sep 19 (UTC)

Okay so you assumed (what is quite likely) that 2002 AA29 consists mostly of stone and less iron. Since the diameter of 60m is quite unsure and the density is only an assumption, the computed mass and gravity parameters should also have a question mark. I see that you used the database from ftp://ftp.lowell.edu/pub/elgb/astorb.html (via your AstOrbBrowser program). I think it would be good to add this link in the reference of each article using these values so that people can see where the values are from. According to http://earn.dlr.de/nea/K02A29A.htm (which is a database of physical parameters of Near Earth asteroids) 2002 AA29 has a diameter of about 50-110 meters. As far as I can see the AstOrb.dat database doesn't provide a value for the diameter of 2002 AA29. I found the 60m diameter value in some press news, which seem to origin in a press release from Jet Propulsion Laboratory: http://www.jpl.nasa.gov/releases/2003/1.cfm . Since this value doesn't get explained further in contrast to the values in the EARN-database I personally trust more the average values of EARN and hesitate to tell any values for mass etc.

Your program sounds very intersting. Unluckily I can't run it at the moment because I don't have any Windows XP installation around here (I'm using Linux only). At the moment there doesn't seem to exist a template for (minor) planets in german wikipedia, although most articles are using the same table layout (which looks good enough for me). There is a new template in discussion at http://de.wikipedia.org/wiki/Wikipedia:Formatvorlage_Astronomisches_Objekt . I'll start a discussion at our astronomy portal about your template and your program. I'm sure it'll be interesting to others as well.

Arnomane

Theia reference?

Paranoid added:

Richard Gott and Edward Belbruno from Princeton University have speculated that 2002 AA29 might have formed together with Earth and Theia.

Who are these people, where is their theory documented, and why is a reference to a theoretical planet which might not even exist not being noted as such? --Phil | Talk 14:51, Nov 19, 2004 (UTC)

They are researchers (as evident from the Princeton reference) and they work in the field astronomy (as evident from the topic). :) The theory is documented in a 74-page paper, a preprint of which is available from arXiv.org (Where Did The Moon Come From). And Theia being "theoretical" doesn't mean it didn't exist. The Giant Impact theory is the current standard, most commonly accepted theory on Moon origins. So the consensus is that Theia did, in fact, exist (most likely, until evidence to the contrary is found), even though we don't know much about it. So I guess my addition could be restored, although adding a reference or reediting it slightly may be needed. Paranoid 15:19, 19 Nov 2004 (UTC)

Those speculations that 2002 AA29 is a product of a collision are founded on some physical parameters of this asteroid:

• It rotates so fast (<33min) that on its surface its gravitational force is weaker than the zentrifugal force, meanig that this body is under mechanic tension. So this asteroid has to be the remenant of a collision. (it is impossible that it has been built out of smaller pieces with such a fast rotation)
• It seems to have an unusual high albedo for an asteroid so it is perhapes a part of the moon or earth.
• Its perfect low eccentricity orbit near earth is indicating that it has been built near earth since most other near earth asteroids coming from the asteroid belt have high eccentricity because gravitational influence by Jupiter and other planets causes such high e orbits. So it is not likely that 2002 AA29 comes from asteroid belt.

Almost all avaliable imformation (and a detailed discussion where this asteroid might come from) of 2002 AA29 is compiled in the german version of this article: de:2002 AA29 (it is one of the eccellent articles there). Even if you can't read german look into the Reference (point "5 Literatur") at the bottom. The articles are english papers from Wiegert, Ostro et al. published in various magazines and further down are links to the entries of 2002 AA29 in databases as MPC-database (orbit parameters) and EARN-database (physical parameters such as diameter and rotation). I personally am somewhat reserved to the specualation that 2002 AA29 is a remenant of the giant impact of Theia and proto-earth, since after that time many asteroids have hit earth and moon (look at night at the craters on the moon ;-) ) and since after such a long time of 4.5*10^9 years the orbits of those rememants from giant impact are heavily disturbed. So it is not that easy to simply look at the orbit parameters and speculate that this is a remenant of the giant impact. (By the way a similar idea was in a readers letter in the recent volume of a german astronomy magazine called "Sterne und Weltraum" (http://www.suw-online.de) and the answer was quite the same). There exist families of asteroids coming from an impact on asteroid 4 Vesta and others in asteroid belt but those impacts happened only about 100 Million years ago. Most probably 2002 AA29 was the result of a collision on moon or earth with a medium asteroid (in the range of 10km diamater). -- Arnomane (in German wikipedia)