Astronomy midterm question: new stars from type II/type Ia supernova remnants?

Astronomy 210 Midterm 2, spring semester 2012
Cuesta College, San Luis Obispo, CA

[Version 1]
[20 points.] An astronomy question on an online discussion board(*) was asked and answered:

owen m: [How c]an another [star] form after a [type II] supernova?
Stom: [W]hen a star...goes [type II] supernova, it blasts a...lot of unused hydrogen out into space...and when there is enough hydrogen pulled together and the gravity gets strong enough the new star burst[s] [into] life...

Discuss why this answer is correct, and how you know this. Explain using the properties and evolution of stars.

*Source: http://answers.yahoo.com/question/index?qid=20090914144056AA43heK.

Solution and grading rubric:

• p = 20/20:
  Correct. Understands that type II supernova remnants are hydrogen rich, discussing hydrogen line spectra evidence and/or that the outer layers of a supergiant are uninvolved in core/shell fusion, and thus are primarily hydrogen, from which a subsequent star can form, and/or may discuss new star formation triggered by type II supernova shockwaves.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Does not directly address why discussion board answer is correct, but at least demonstrates understanding of type II supernova process.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on type Ia supernova or other types of stars/supernovae, or focuses on star formation only instead of also discussing hydrogen contribution from type II supernovae.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. May describe/restate discussion board answer without substantive explanation involving properties and evolution of stars as to why it is correct.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30676
Exam code: midterm02sA4r
p: 10 students
r: 5 students
t: 12 students
v: 7 students
x: 4 students
y: 0 students
z: 0 students

A sample "p" response (from student 2448):

[Version 2]
[20 points.] An astronomy question on an online discussion board(*) was asked and answered:

owen m: [How c]an another [star] form after a [type Ia] supernova?
Stom: [W]hen a star...goes [type Ia] supernova, it blasts a...lot of unused hydrogen out into space...and when there is enough hydrogen pulled together and the gravity gets strong enough the new star burst[s] [into] life...

Discuss why this answer is incorrect, and how you know this. Explain using the properties and evolution of stars.

*Source: http://answers.yahoo.com/question/index?qid=20090914144056AA43heK.

Solution and grading rubric:

• p = 20/20:
  Correct. Understands that type Ia supernova remnants are hydrogen poor, discussing hydrogen line spectra evidence and/or that the carbon-oxygen white dwarf steals hydrogen from a companion star, and fuses these to heavier elements when exploding, leaving very little (if any) hydrogen from which a subsequent star can form.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Does not directly address why discussion board answer is incorrect, but at least demonstrates understanding of type Ia supernova process.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on type Ia supernova or other types of stars/supernovae, or focuses on star formation only instead of also discussing hydrogen contribution from type II supernovae.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. ay describe/restate discussion board answer without substantive explanation involving properties and evolution of stars as to why it is incorrect.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
Exam code: midterm02n4Rg
p: 8 students
r: 0 students
t: 11 students
v: 11 students
x: 3 students
y: 0 students
z: 0 students

A sample "p" response (from student 7538):