"P-dog" scribble

"P-dog" by L. M.
Astronomy 210L
Fall Semester 2008
Cuesta College, San Luis Obispo, CA

This doodle was found on the back of an introductory astronomy exam, presumably a caricature of the instructor.

Extraterrestrial hypothesis tryptich

081206-1060907-invert
http://www.flickr.com/photos/waiferx/3087116819/
Originally uploaded by Waifer X

081206-1060910-invert
http://www.flickr.com/photos/waiferx/3087119633/
Originally uploaded by Waifer X


081206-1060911-invert
http://www.flickr.com/photos/waiferx/3088597420/
Originally uploaded by Waifer X

Dramatizations of the original 1974 Arecibo message, the Drake equation, and the purported 2001 Chibolton crop circle "reply."

Erasing slate: like life?

"If only life was like erasing slate." by Anonymous
December 1, 2008
Cuesta College, San Luis Obispo, CA

Latest scribbling on the lift-and-erase slate in the hallway, outside the office door.

Astronomy midterm question: no-center universe expansion

Astronomy 210 Midterm 2, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss why the expansion for the universe has no center, using observations and evidence related to the Hubble law in your explanation.

Solution and grading rubric:

• p = 20/20:
  Correct. Argument involves redshifts (and thus recession velocities) being proportional to distances (i.e., Hubble's law), and how this implies that there is no unique center, any other galaxy would observe a similar Hubble's law. May also invoke no-edge, no-center argument of an non-finite universe.
  
• 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.
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 23 students
r: 3 students
t: 2 students
v: 2 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response, discussing Hubble's law (from student 1225):

Another "p" response, discussing "Cosmic Haterade" (from student 7120):

Astronomy midterm question: star cluster age

Astronomy 210 Midterm 2, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[20 points.] Shown at right is an H-R diagram of a star cluster, where all of these stars have the same age. Discuss whether this star cluster is very young or is very old, and explain why.

Solution and grading rubric:

• p = 20/20:
  Correct. Massive stars evolve quickly, and have already gone through their main sequence lifetimes to the supergiant stage, so this cannot be a very young star cluster. Low mass stars evolve slowly, so for these stars to have reached the main sequence, this must be a very old star cluster.
  
• 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. May state that this is a young star cluster, but understands how massive and low mass stars evolve differently.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Uses other criteria to determine age of star cluster.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 14 students
r: 1 student
t: 11 students
v: 3 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response, discussing the "house party" analogy of how stellar evolution rates depend on mass (from student 3089):

Astronomy midterm question: different temperature, same luminosity stars

Astronomy 210 Midterm 2, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[20 points.] Two stars have the same luminosity, but different temperatures. Explain whether the hotter star or the cooler star is larger in size, using the Stefan-Boltzmann law and/or an H-R diagram.

Solution and grading rubric:

• p = 20/20:
  Correct. According to the Stefan-Boltzmann law, the luminosity of a star is proportional to its size (surface area) and its temperature, raised to the fourth power. Thus for the cooler star to have the same luminosity as a hotter star, the cooler star must be much larger in size.
  
• 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.
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion of concepts other than the Stefan-Boltzmann law, such as stellar evolution rates, pressure-temperature thermostat, etc.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 21 students
r: 3 students
t: 0 students
v: 6 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response, graphically demonstrating the dependence of luminosity on size and temperature (from student 0228):

A sample "p" response, using an H-R diagram (from student 1186):

Another "p" response, using two specific stars as examples (from student 2020):

A "p" response organizing the Stefan-Boltzmann law in tabular form (from student 8187):

Venus and Jupiter pair up with waxing crescent Moon

081130-1060831
http://www.flickr.com/photos/waiferx/3073185079/
Originally uploaded by Waifer X


081130-1060832
http://www.flickr.com/photos/waiferx/3073186081/
Originally uploaded by Waifer X


081130-1060836
http://www.flickr.com/photos/waiferx/3073186499/
Originally uploaded by Waifer X


081130-1060843
http://www.flickr.com/photos/waiferx/3073186951/
Originally uploaded by Waifer X


Venus, Jupiter, and the waxing crescent Moon on November 30, 2008, seen from Turlock, CA. Photos taken with a Panasonic Lumix LZ-8 in night scene mode, with 10 second timer to avoid shudder.

Binary star masses

081129-1060829-invert
http://www.flickr.com/photos/waiferx/3069568005/
Originally uploaded by Waifer X

Proper motion data of Sirius A and B, used to determine their masses using Kepler's third law.

Cream-in-coffee model: Jupiter vs. Saturn

081126-1060756
http://www.flickr.com/photos/waiferx/3062504322/
Originally uploaded by Waifer X

Cream-in-coffee model of Jupiter and Saturn weather patterns. Jupiter's core is hotter, and has more active convection and weather patterns, as evidenced by the self-mixing of cream in the cup of hot coffee, compared to Saturn's cooler core, which has less active convection and weather patterns, seen by the settling cream in the cup of cold coffee. (The secondary effect of sunlight bringing the cloud levels higher in Jupiter above the hydrogen haze, compared to Saturn is not modeled here.)