Astronomy midterm question: plausible IAU classification of 300163 (2006 VW139) before breaking apart?

Astronomy 210 Midterm 2, fall semester 2017
Cuesta College, San Luis Obispo, CA

An international team of astronomers recently discovered two asteroids with comet-like features orbiting each other in the asteroid belt:

NASA's Hubble Space Telescope helped an international team of astronomers find that an unusual object in the asteroid belt, designated 300163 (2006 VW139), is in fact two asteroids of almost the same mass and size, orbiting each other at a distance of 60 miles. They also have comet-like features, including a bright halo of material, called a coma, and a long tail of dust. Roughly 5,000 years ago, 300163 (2006 VW139) probably broke into these two pieces due to a fast rotation.[*]

Before it broke apart 5,000 years ago, discuss how 300163 (2006 VW139) might have been originally classified, using the International Astronomical Union classification scheme. Clearly state your assumptions about what properties 300163 (2006 VW139) might have had before it broke apart.

[*] J. Agarwal, "Comet or Asteroid? Hubble Discovers that a Unique Object is a Binary," hubblesite.org/news_release/news/2017-32.

Solution and grading rubric:

• p:
  Correct. Discusses IAU classification scheme to argue that before breaking up 5,000 years ago:
  1. 300163 (2006 VW139) was in the asteroid belt, orbiting the sun, and thus could not have been a moon; and not having been able to gravitationally dominate its orbit by clearing asteroids out or pulling in asteroids into itself, could not have have been a planet (assuming that it had a rounded shape); and
  2. depending on whether its shape was irregular or rounded, it would have either been classified as solar system debris or a dwarf planet.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May have instead discussed how the two components of 300163 (2006 VW139) today could be categorized in terms of the IAU classification scheme, instead of how it might have been categorized before breaking up 5,000 years ago.
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Explicitly lists IAU requirements, but does not apply them correctly/consistently.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion only tangentially related to the IAU classification scheme.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion unrelated to the IAU classification scheme.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 70158
Exam code: midterm02Sm5n
p: 35 students
r: 4 students
t: 5 students
v: 2 students
x: 0 students
y: 0 students
z: 0 students

Section 70160
Exam code: midterm02nJv3
p: 23 students
r: 5 students
t: 3 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 0987):
Another sample "p" response (from student 1796):
A sample "r" response (from student 1881), discussing the current classification of 300163 (2006 VW139) today: