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: determining distance from apparent and absolute magnitudes (1)

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

The following claim was made by a student on an astronomy exam[*]:

0725: Let's say a star had an apparent magnitude of –1.5 and an absolute magnitude of +1.5. The star has to be closer than 10 parsecs from Earth.

Discuss whether this claim is correct or incorrect, and how you know this. Explain using the relationships between apparent magnitude, absolute magnitude, and distance.

[*] waiferx.blogspot.com/2008/11/astronomy-midterm-question-apparent.html.

Solution and grading rubric:

• p:
  Correct. Understands difference between apparent magnitude m (brightness as seen from Earth, while at its actual distance from Earth) and absolute magnitude M (brightness as seen from Earth, when placed at the "fair comparison distance" of 10 parsecs away), and discusses:
  1. the star's apparent magnitude of m = −1.5 is brighter than its absolute magnitude of M = +1.5; so
  2. the star must be located closer than 10 parsecs away, as moving it from its actual location (where m = −1.5) to 10 parsecs (where M = +1.5) makes it dimmer; such that
  3. the student's claim is correct.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Has both (1)-(2) complete and correct, but somehow concludes that student's claim is incorrect, or does not sufficiently discuss the correctness/incorrectness about the student's claim.
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least discussion demonstrates understanding of relationships between apparent magnitudes, absolute magnitudes, and distances. At least discussion demonstrates understanding of relationships between apparent magnitudes, absolute magnitudes, and distances. Has only one of (1)-(2) complete and correct, the other is problematic.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use relationships between apparent magnitudes, absolute magnitudes, and distances. Both (1) and (2) are problematic.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion based on garbled definitions of, or not based on proper relationships between apparent magnitudes, absolute magnitudes, and distances.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 70158
Exam code: midterm02Rf0w
p: 23 students
r: 4 students
t: 1 student
v: 0 students
x: 6 students
y: 0 students
z: 0 students

A sample "p" response (from student 1492):

Astronomy midterm question: determining distance from apparent and absolute magnitudes (2)

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

The following claim was made by a student on an astronomy exam[*]:

7734: If a star has an absolute magnitude of +20, but when seen from Earth has an apparent magnitude of +5, the star must be very close to us.

Discuss why this claim is incorrect, and how you know this. Explain using the relationships between apparent magnitude, absolute magnitude, and distance.

[*] waiferx.blogspot.com/2010/11/astronomy-midterm-question-apparent.html.

Solution and grading rubric:

• p:
  Correct. Understands difference between apparent magnitude m (brightness as seen from Earth, while at its actual distance from Earth) and absolute magnitude M (brightness as seen from Earth, when placed at the "fair comparison distance" of 10 parsecs away), and discusses:
  1. the star's apparent magnitude of m = +5 is brighter than its absolute magnitude of M = +20; so
  2. the star must be located closer than 10 parsecs away, as moving it from its actual location (where m = +5) to 10 parsecs (where M = +20) makes it dimmer; such that
  3. the student's claim is correct.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Has both (1)-(2) complete and correct, but somehow concludes that student's claim is incorrect, or does not sufficiently discuss the correctness/incorrectness about the student's claim.
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least discussion demonstrates understanding of relationships between apparent magnitudes, absolute magnitudes, and distances. At least discussion demonstrates understanding of relationships between apparent magnitudes, absolute magnitudes, and distances. Has only one of (1)-(2) complete and correct, the other is problematic.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use relationships between apparent magnitudes, absolute magnitudes, and distances. Both (1) and (2) are problematic.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion based on garbled definitions of, or not based on proper relationships between apparent magnitudes, absolute magnitudes, and distances.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 70160
Exam code: midterm02T4qz
p: 7 students
r: 4 students
t: 6 students
v: 3 students
x: 2 students
y: 0 students
z: 0 students

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

Astronomy midterm question: comparing sizes, temperatures of same-luminosity stars

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

The following claim was made by a student on an astronomy exam[*]:

2881: If two stars have the same luminosity, the star with the lower temperature must be larger.

Discuss whether this claim is correct or incorrect, and how you know this. Explain using Wien's law, the Stefan-Boltzmann law and/or an H-R diagram.

[*] waiferx.blogspot.com/2009/05/astronomy-midterm-question-cooler.html.

Solution and grading rubric:

• p:
  Correct. Discusses how the H-R diagram and/or the Stefan-Boltzmann law (luminosity is proportional to size × Temperature⁴) demonstrates that in order for a cooler star to have the same luminosity as a hotter star, its lower temperature must be compensated for by having a larger size; thus the claim by that student is correct.
  
• 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.
  
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use Wien's law, the Stefan-Boltzmann law, and/or H-R diagram. May have argument based on the size of a star being dependent on luminosity and temperature.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion not clearly based on Wien's law, the Stefan-Boltzmann law, and/or H-R diagram.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Section 70158
Exam code: midterm02Rf0w
p: 31 students
r: 1 student
t: 0 students
v: 1 student
x: 1 student
y: 0 students
z: 0 students

Section 70160
Exam code: midterm02T4qz
p: 16 students
r: 2 students
t: 0 students
v: 2 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 0809), using the Stefan-Boltzmann law:
A sample "p" response (from student 1234), using a Hertzsprung-Russell diagram:
A sample "p" response (from student 1278) using both the Stefan Boltzmann law and a Hertzsprung-Russell diagram:
A sample "x" response (from student 4000), appealing to concepts other than than of the Stefan-Boltzmann law:

Physics quiz archive: simple harmonic motion, waves

Physics 205A Quiz 6, fall semester 2019
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855 version 1
Exam code: quiz06co6O



Sections 70854, 70855 results

0- 6 :	* [low = 3]
7-12 :	****
13-18 :	*************
19-24 :	**************** [mean = 22.1 +/- 6.1]
25-30 :	****************** [high = 30]

Astronomy quiz archive: stellar evolution

Astronomy 210 Quiz 6, fall semester 2019
Cuesta College, San Luis Obispo, CA

Section 70158
Exam code: quiz06sOr6


Section 70158

0- 8.0 :
8.5-16.0 :	**** [low = 13.5]
16.5-24.0 :	******
24.5-32.0 :	************ [mean = 27.5 +/- 6.9]
32.5-40.0 :	************ [high = 36.5]

Section 70160
Exam code: quiz06NyQ7


Section 70160

0- 8.0 :
8.5-16.0 :	****** [low = 11]
16.5-24.0 :	****** [mean = 21.7 +/- 6.8]
24.5-32.0 :	*******
32.5-40.0 :	** [high = 33]

Physics quiz archive: rotations, torque, pressure, buoyancy, fluid flow

Physics 205A Quiz 5, fall semester 2019
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, version 1
Exam code: quiz05Gu1L



Sections 70854, 70855 results

0- 6 :	** [low = 6]
7-12 :	*********
13-18 :	***********
19-24 :	***************** [mean = 19.8 +/- 6.3]
25-30 :	************* [high = 27]