Vulcanoid object characteristics

Thank you for sharing your questions and thoughts on Vulcanoid properties.  Lets look each of them in turn:

1. "Cannot be a captured iron meteor. The sun's magnetic field would cause magnetic braking drag and create an unstable spiral orbit.

I am afraid that your assumption about the impact of the Sun's magnetic field on Vulcanoid asteroids is incorrect. The orbit of an object within the stable Vulcanoid zone (see FAQ 1.3) would not be significantly impacted by the Sun's magnetic field. Even at 0.08 a.u.i, the Sun's magnetic field is not strong enough to perturb a reasonable sized asteroid by very much.

The simulations by Neil Wyn W. Evans (University of Oxford) and Serge A. Tabachnik (Princeton University Observatory) show that Vulcanoids can reside in the stable Vulcanoid zone for several Gyr (several 10⁹ years).  They showed that the dynamical forces on objects closer than 0.08 a.u. were dominated by things such as the Yarkovsky effect and other solar transport forces. The Sun's magnetic field was not one of the significant forces impacting objects closer than 0.08 a.u. so its influence on objects farther away will be even less.

Another way to look at it is this: A conductive asteroid moving through the Sun's magnetic field would produce surface and near surface electric currents. This surface current would produce a magnetic filed that would interact with the Sun's magnetic field and impart a force on the asteroid.  However, while the force due to the surface current is a function of the surface area, the impact of that force is a function of the mass of the asteroid. Therefore, the magnetic force goes up by the square of the radius of the asteroid, but its ability to accelerate the asteroid out of its orbit goes down by the cube of the radius. While Sun's magnetic field could perturb tiny conductive specks of conductive dust, its ability to perturb larger objects goes down as their radius goes up. By the time you reach an asteroid of any significant size (say 10m, let alone 1km in radius), the magnetic force has become insignificant.

2. "The Vulcanoid would most likely be similar in composition to a carbonaceous chondrite meteor

Vulcanoids that formed and stayed in the stable Vulcanoid zonei are likely to be Mercuryi-like in composition if not more dense. Primordial Vulcanoids are likely to have a high iron and nickel content. Mercury itself is about 70% metallic and 30% silicate in composition. Primordial Vulcanoids might even be more metallic in composition. This assumes that our basic model of conditions in the early solar system (based on observations of other stars and proto-stars) is correct of course!

C-type (carbonaceous, 75% of known asteroids) and S-type (silicaceous, 17% of known asteroids) could wander into and stay within the stable Vulcanoid zone.  It is highly probable that some Vulcanoids would be C-Type or S-type. However, the majority of the primordial Vulcanoids should be M-type (metallic).

3. "Orbital dynamics of the sun-mercury gravitational system would indicate an unstable highly eccentric orbital plane. This would indicate that determining orbital parameters are going to be very difficult resulting in lost / found object searches.

The Evans-Tabachnik model showed that Vulcanoids with a mean distance from the Sun of > 0.18 a.u. would be removed from their orbit by the influence of Mercury, Venus and Earth (in order of significance) over time. They showed that an object with a mean distancei of 0.21 a.u., for example, would be expelled from the Vulcanoid zone after several 100 Myri (several 10⁸ years). Objects with a mean distance is < 0.18 a.u. could reside in the stable Vulcanoid zone for several Gyri (several 10⁹ years).

Obviously highly eccentric orbits that moved well outside of the stable Vulcanoid zone would be object to solar dynamical and inner solar system gravitational forces that would move then out of their orbits over time. However, their orbits would not be so erratic as to make their orbits difficult to track in the short term.

Because highly eccentric Vulcanoid orbits and Vulcanoids whose mean distance is outside of the stable Vulcanoid zone cannot last for the long term (several Gyr), we may safely conclude that nearly all Vulcanoids must reside within the stable Vulcanoid zone, and that their orbits would be as traceable as any other minor planet (once you find them of course!). Moreover, their orbits should not be too eccentric: although an orbit that goes between 0.08 a.u. (or slightly less) and 0.18 a.u. (or slightly more) could be multi Gyr stable.  Such an orbit would be likely the most extreme that might be found of any long-term non-temporary Vulcanoid.

Thanks for posting your thoughts on Vulcanoid properties, Mitch.  I hope this helps.

chongo (Landon Curt Noll - http://www.isthe.com/astro.html) /\oo/\