20181004

Astronomy midterm question: early evening Arcturus and Spica high in the sky at start of a season?

Astronomy 210 Midterm 1, fall semester 2018
Cuesta College, San Luis Obispo, CA

An astronomy magazine article[*] describes the positions of star and constellations in the sky at a certain time of year:
Arcturus and Spica are the two brightest stars in the constellations Boötes and Virgo. Both are now superbly placed high in the sky in the early evening at the start of this season.
Discuss at the start of which season (spring/summer/fall/winter) would be the most plausible for an observer in San Luis Obispo, CA to see Arcturus and Spica high in the sky in the early evening. If there is no such plausible start of a season, then explain why. Defend your answer by clearly explaining how you used your starwheel to do this, along with any assumptions that you may have made. (Ignore daylight saving time.)

[*] "Sky Maps: December 2016-December 2017," Skywatch (2017), p. 20.

Solution and grading rubric:
  • p:
    Correct. Discussion includes the following:
    1. turns starwheel such that Arcturus and Spica are "placed high in the sky" (at or near the meridian);
    2. reads off a plausible date corresponding to a time in the "early evening" (6 PM-9 PM?); and
    3. relates this date to a specific start of a season (in this case, late June, hence the start of summer).
    May argue that this sky in the early evening does not exactly coincide with the exact start of summer (or any season), and thus no start of any season is possible.
  • r:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May have interpreted "early evening" to be 5 PM-6 PM, and thus picks mid-August as the "start(?) of fall."
  • t:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Picks October or November in the early evening, but this places Arcturus and Spica low in the western sky, and not "placed high in the sky."
  • v:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use starwheel in a systematic manner.
  • x:
    Implementation/application of ideas, but credit given for effort rather than merit. Discussion not clearly based on using a starwheel in a systematic manner.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Section 70158
Exam code: midterm01Sa1Y
p: 19 students
r: 6 students
t: 0 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

Section 70160
Exam code: midterm01n4mR
p: 17 students
r: 4 student
t: 13 students
v: 0 students
x: 2 students
y: 1 student
z: 0 students

A sample "p" response (from student 1168)

Another sample "p" response (from student 4747)

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