P-dog's blog: boring but important: 200911

20091130

Astronomy midterm question: centers of the universe

Astronomy 210 Midterm 2, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Consider the following comment:

"The Universe has as many different centers as there are living beings in it. Each of us is a center of the Universe..."
—Aleksander Isaevich Solzhenitsyn, The Gulag Archipelago: 1918-1956, Harper & Row Publishers, 1985, p. 3.

Discuss why observers in different galaxies would each think that they are the center of expansion for the universe. Explain using Hubble's law.

Solution and grading rubric:

p = 20/20:
Correct. Explains how Hubble's law (recession velocity is proportional to distance) corresponds to the expansion of space between galaxies, such that each galaxy seems to be center of expansion as observed from their position. May use analogies as not-like-an-explosion, raisin bread, enlargement of between-spaces, etc.
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. Typically Hubble's law discussion is missing or problematic.
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 70158
p: 16 students
r: 11 students
t: 20 students
v: 4 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 8260):

Another sample "p" response (from student 1989):

A sample "t" response (from student 1781), with no explicit discussion of Hubble's law, but still capturing the essence of the relativeness of galaxies receding from all observers::

A sample "v" response (from student 2522), appealing to a version of the Copernican principle:

Astronomy midterm question: globular cluster metallicity

Astronomy 210 Midterm 2, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss whether globular cluster stars in the halo of the Milky Way are expected to be metal-rich or metal-poor, and why. Explain using the properties of mass and stellar lifetimes, and the Milky Way.

Solution and grading rubric:

p = 20/20:
Correct. Globular cluster stars in the halo are the old first-generation stars that formed when the Milky Way was spherical in shape and are composed primarily of hydrogen with little metal content, as metal content increases over time due to stars fusing and releasing fusion products to subsequent generations.
r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Complete explanation of why metal-poor stars are older than metal-rich stars, but discussion of why the halo is the oldest part of the Milky Way is problematic, or vice versa.
t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. As (r), but discussion of why the halo is the oldest part of the Milky Way is missing, or vice versa.
v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Has only problematic discussion of how metal-poor stars are old stars (e.g., metals are used up by stars over time).
x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit. Implausible evidence/methods/discussion.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 70158
p: 14 students
r: 6 students
t: 9 students
v: 22 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 9221), with a fanciful depiction of increasing metallicity in subsequent generations of stars:

A more conventional sample "p" response (from student 1520):

Another sample "p" response (from student 1204), illustrating the monolithic collapse model:

A sample "v" response (from student 6636), typically discussing how stars use up metals over time to eventually become old and metal-poor:

Astronomy midterm question: same luminosity giant and main-sequence stars

Astronomy 210 Midterm 2, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss whether or not a giant star and a main sequence star could have the same luminosity, and why. Support your answer using Wien's law and/or the Stefan-Boltzmann law.

Solution and grading rubric:

p = 20/20:
Correct. Discusses how the Stefan-Boltzmann law (luminosity (brightness) proportional to size * (Temperature)^4) explains that two stars can have the same luminosity if the smaller star is hotter, and the larger star is cooler.
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. At least recognizes how the Stefan-Boltzmann law is applicable, but argument is garbled (e.g., has giant star smaller but hotter than main sequence star of the same luminosity).
v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least recognizes how size and temperature are relevant, but Stefan-Boltzmann law itself is garbled.
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 70158
p: 32 students
r: 6 students
t: 3 students
v: 6 students
x: 4 students
y: 0 students
z: 0 students

A sample "p" response (from student 8260) using both details from an H-R diagram (provided with the midterm), and a table comparing relative luminosities, sizes, and temperatures in the Stefan-Boltzmann law:

A sample "r" response (from student 5678), with the giant correctly being larger and cooler than (but the same luminosity as) a main-sequence star, but with a garbled quantitative expression of the Stefan-Boltzmann law:

A sample "v" response (from student 0733), mangling the comparative size and temperatures:

Another sample "v" response (from student 1030), at least recognizing that size and temperature are relevant factors:

A sample "v" response (from student 3803), while recognizing that size and temperature are relevant factors, also explicitly points out that these two stars indeed can have the same luminosity, as demonstrated on an H-R diagram:

A sample "x" response (from student ), discussing factors other than size and temperature:

20091124

Astronomy current events question: Phoenix lander status

Astronomy 210L, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)

Astronomy.com editors, "Frost-Covered Phoenix Lander Seen in Winter Images," November 5, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8778

The NASA Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment camera has recently observed the NASA Phoenix Lander:
(A) stuck between two medium-sized boulders.
(B) covered by dry-ice frost.
(C) sinking in quicksand.
(D) surrounded by rising waters from melting ice.
(E) currently enroute to salvaging parts from the NASA Mars Spirit Rover.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 5 students
(B) : 42 students
(C) : 3 students
(D) : 5 students
(E) : 4 students

Astronomy current events question: upper atmosphere dust samples

Astronomy.com editors, "'Ultra-Primitive' Particles Found in Comet Dust," November 2, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8767

According to Carnegie Institute researchers, dust samples collected by high-flying aircraft in the upper atmosphere contain:
(A) evidence that a global cooling cycle is starting.
(B) material from a new atmospheric layer of carbon dioxide.
(C) material from stars that existed before the birth of our solar system.
(D) characteristics of lunar soil samples.
(E) pollen grains and seeds from before the dinosaur extinction.

Correct answer: (E)

Student responses
Sections 70178, 70186, 70200
(A) : 1 student
(B) : 7 students
(C) : 43 students
(D) : 3 students
(E) : 2 students

Astronomy current events question: cosmic ray origin

Astronomy.com editors, "VERITAS Telescope Array Helps Solve The Origin of Cosmic Rays," November 2, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8766

Researchers using evidence from the Very Energetic Radiation Imaging Telescope Array System (VERITAS) have determined that cosmic rays are:
(A) the product of processes deep within Earth's core.
(B) caused by the decay of unstable, ultraheavy elements.
(C) antimatter particles from the big bang.
(D) photons emitted by quasars.
(E) protons accelerated by exploding stars and stellar winds.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 2 students
(B) : 3 students
(C) : 3 students
(D) : 6 students
(E) : 44 students

20091117

Astronomy current events question: Fermi space telescope gamma rays

Ivan Semeniuk, "Is Fermi Seeing Dark Matter?," October 28, 2009
http://www.skyandtelescope.com/community/skyblog/semeniuk/66968132.html

According to Harvard researchers, gamma rays detected by the space-based Fermi Large Area Telescope may indicate the presence of:
(A) dark energy.
(B) dark matter.
(C) Nibiru, a planetoid supposedly colliding with Earth in 2012.
(D) a new supermassive black hole near the Milky Way center.
(E) technological sources of nuclear energy being released.

Correct answer: (B)

Student responses
Sections 70178, 70200
(A) : 2 students
(B) : 34 students
(C) : 1 student
(D) : 2 students
(E) : 4 students

20091116

Astronomy current events question: notable gamma ray burst

Alan MacRobert, "Blast from the Very Far Past," October 28, 2009
http://www.skyandtelescope.com/community/skyblog/newsblog/66941457.html

What is notable about the gamma ray burst detected by the Gemini North Telescope in Hawaii last April, recently published in a peer-reviewed journal?
(A) Most energetic explosion known.
(B) Disputed as an instrument calibration error.
(C) Echo of the original big bang.
(D) Seen to be evolving backwards in time.
(E) Earliest explosion yet observed.

Correct answer: (E)

Student responses
Section 70178
(A) : 3 students
(B) : 2 student
(C) : 5 students
(D) : 2 students
(E) : 8 students

20091115

Astronomy current events question: Indonesian atmospheric blast

Kelly Beatty, "Cosmic Blast Rattles Indonesia," October 25, 2009
http://www.skyandtelescope.com/community/skyblog/newsblog/65960457.html

What have scientists determined to be most likely cause of an atmospheric blast over Indonesia in early October?
(A) Asteroid fragment.
(B) Stray antimatter particles.
(C) Gamma ray burst.
(D) The Large Hadron Collider in Switzerland.
(E) Reentering rocket booster.

Correct answer: (A)

Student responses
Section 70200
(A) : 20 students
(B) : 1 student
(C) : 2 students
(D) : 0 students
(E) : 0 students

20091106

Astronomy current events question: accused spy/planetary science researcher

Richard A. Kerr, "Accused Spy Was Hot on Trail of Lunar Ice," October 20, 2009
http://blogs.sciencemag.org/scienceinsider/2009/10/accused-spy-was.html

A U.S. planetary scientist charged with attempting to sell classified information was previously involved with investigating what feature of the moon?
(A) Subsurface ice in shadowed craters.
(B) Detection of stranglets in Apollo mission lunar soil samples.
(C) Supposed nuclear blast tests on the far side.
(D) Falsification of Apollo mission moon landings.
(E) Disputed theories of the origin of the moon.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 22 students
(B) : 2 students
(C) : 2 students
(D) : 0 students
(E) : 2 students

20091105

Astronomy current events question: latest exoplanet discoveries

Alan MacRobert, "And Then There Were 400," October 21, 2009
http://www.skyandtelescope.com/news/65056162.html

How did the European Space Observatory in La Silla, Chile detect the 30 newest exoplanets, bringing the known total to over 400?
(A) Reflected radio signals from Voyager 1/2 probes.
(B) Observing these planets passing in front of their stars.
(C) Wobbles these planets exert on their stars.
(D) Laser light reflected off these planets.
(E) Radio signals from planetary magnetic storms.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 8 students
(B) : 14 students
(C) : 41 students
(D) : 4 students
(E) : 1 student

P-dog's blog: boring but important