Astronomy midterm question: possible IAU classification of primordial black hole in Kuiper belt?

Astronomy 210 Midterm 2, fall semester 2019
Cuesta College, San Luis Obispo, CA

Consider the speculative statements below as factual:

Scientists think the gravitational pull of something in the outer solar system could be yanking Kuiper belt objects into strange orbits. This object is said to have a mass about 10 times that of Earth and an orbit around the sun 20 times farther out than Neptune's. A team of scientists led by Durham University claim it's a primordial black hole about the size and shape of a bowling ball.[*]

Based on the information given in this excerpt, discuss whether or not this "primordial black hole" could be considered a planet, and why. Explain using the International Astronomical Union classification scheme.

[*] Harry Pettit, "Mysterious Planet X May Be Black Hole That's '10 times Heavier than Earth but the Size of a Bowling ball' on Edge of Our Solar System" (September 30, 2019), thesun.co.uk/tech/10032900/planet-x-black-hole-solar-system/.

Solution and grading rubric:

• p:
  Correct. Discusses IAU classification scheme to argue that this primordial black hole would meet each of the qualifications:
  1. orbits the sun directly (20 times farther out than Neptune's orbit);
  2. has a spherical shape (like a bowling ball);
  3. dominates its orbit (gravitationally pulling Kuiper belt objects into strange orbits);
  such that it should be classified as a planet.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May have overlooked or misinterpreted the gravitational influence of this primordial black hole on Kuiper belt objects.
• 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 based on garbled definitions of, or not based on proper or complete list of the IAU qualifications.
• 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: midterm02Rf0w
p: 25 students
r: 8 students
t: 1 student
v: 0 students
x: 0 students
y: 0 students
z: 0 students

Section 70160
Exam code: midterm02T4qz
p: 15 students
r: 5 students
t: 1 student
v: 1 student
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 5622):
Another sample "p" response (from student 7890):

Astronomy midterm question: possible IAU classification of "cubewano" 2014 MU69?

Astronomy 210 Midterm 2, spring semester 2019
Cuesta College, San Luis Obispo, CA

A "cubewano" is defined as a Kuiper belt object whose orbit around the sun is not gravitationally controlled by Neptune or other planets[*]. Discuss whether or not a "cubewano" such as 2014 MU₆₉ (nicknamed "Ultima Thule," shown at right[**]) could be considered a dwarf planet, and why. Explain using the International Astronomical Union classification scheme.

[*] wiki.pe/Cubewano.
[**] nasa.gov/sites/default/files/thumbnails/image/ultima-thule-1-ca06_022219.png.

Solution and grading rubric:

• p:
  Correct. Discusses IAU classification scheme to argue that 2014 MU₆₉ would meet qualification I (orbits the sun directly), but with its irregular shape would not meet qualification II (rounded shape), and thus be classified as solar system debris. (Note that as a Kuiper belt object, 2014 MU₆₉ does not meet qualification III (dominates its orbit), but this does not affect its solar system debris classification. But may instead interpret 2014 MU₆₉'s shape is "round enough" in order to conclude that it would 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 30676
Exam code: midterm02SpsR
p: 27 students
r: 4 students
t: 5 students
v: 3 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 7563):

Astronomy midterm question: possible IAU classification of "twotino" 2002 WC19?

Astronomy 210 Midterm 2, spring semester 2019
Cuesta College, San Luis Obispo, CA

A "twotino" is defined as a Kuiper belt object whose orbit around the sun is periodically perturbed by Neptune's gravity[*]. Discuss whether or not a "twotino" such as 
2002 WC₁₉ (shown at right[**], as depicted by an artist) could be considered a dwarf planet, and why. Explain using the International Astronomical Union classification scheme.

[*] wiki.pe/Twotino.
[**] se-database.fandom.com/wiki/2002_WC19.

Solution and grading rubric:

• p:
  Correct. Discusses IAU classification scheme to argue that 2002 WC₁₉ would meet qualification I (orbits the sun directly), and appear to meet qualification II (rounded shape), but does not meet qualification III (dominates its orbit), it would 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 30674
Exam code: midterm02nwF7
p: 19 students
r: 1 student
t: 7 students
v: 4 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 2815):

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):

Presentation: solar system motions

Galileo's observations of moons orbiting Jupiter. This did not necessarily disprove that Earth is at the center of motion in the solar system, but it made it much more plausible that Earth could move (around the sun) and not leave the moon behind, if Jupiter could move and not leave its moons behind.

The phases that Venus undergoes, which was also observed by Galileo. Note that Venus appears completely black when silhouetted against the sun as it passes between Earth and the sun, and Venus gibbous phases when it is going around behind the sun. This was the ultimate proof that Earth was not the sole center of motion in the solar system if Venus and other planets exhibit phases as they orbit the sun.