Astronomy midterm question: possible IAU classification of "rounded" 2006 RH120?

Astronomy 210 Midterm 2, fall semester 2018
Cuesta College, San Luis Obispo, CA

2006 RH₁₂₀ (previously known as "6R10DB9") is an object that orbits the sun most of the time, but periodically is caught by Earth's gravity to make several loops around Earth, before returning back to its normal orbit around the sun:

Is 2006 RH₁₂₀ a "second moon?" I'd call it a chunk of rock that orbits the sun almost all the time, spending only a few months orbiting Earth in 2006. It will make passes by us in 2028 and 2044 (at safe distances), and every twenty years or so after that. Eventually, it'll get caught for a few orbits around Earth again, and will almost certainly be ejected again, just as happened this time. 2006 RH₁₂₀ quite likely got where it is as a result of being blasted off the surface of the moon by an impact.[*][**]

In the (unlikely) event that 2006 RH₁₂₀ is found to have a rounded shape, discuss how it should be classified when it is in its usual orbit around the sun. Explain using the International Astronomical Union classification scheme.

[*] projectpluto.com/pluto/mpecs/6r1.htm.
[**] Illustration credit: Gregg Dinderman, skyandtelescope.com/astronomy-news/earths-other-moon/.

Solution and grading rubric:

• p:
  Correct. Discusses IAU classification scheme to argue that 2006 RH₁₂₀ when in its usual orbit around the sun would pass qualification I (orbits the sun directly), and with a presumably (however unlikely) rounded shape would pass qualification II (rounded shape), but as it is periodically captured by Earth's gravity 2006 RH₁₂₀ does not dominate its orbit, and thus would presumably be classified as a dwarf planet.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
• 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: midterm02SYnR
p: 29 students
r: 0 students
t: 0 students
v: 4 students
x: 0 students
y: 1 student
z: 1 student

Section 70160
Exam code: midterm02NdI0
p: 6 students
r: 2 students
t: 6 students
v: 3 students
x: 1 student
y: 0 students
z: 0 students

A sample "p" response (from student 4073):