"While the silent Heavens roll, and the Suns upon their fiery way,
All their planets whirling round them, flash a million miles a day."
--Alfred, Lord Tennyson, "Locksley Hall Sixty Years After," Locksley Hall
Sixty Years After; The Promise of May; Tiresias and other Poems,
Tauchnitz (1887), p. 31.
Equipment
Cuesta ThinkPad laptops (wireless networking, internet browser)
(appropriate, responsible in-class use of personal laptops allowed)
Current Events Quiz
(First 10 minutes of laboratory.)
Briefing
Studying Extrasolar Planets (*.blog)
Kepler's Tally of Planets (*.html)
(The New York Times)
Big Idea
Extrasolar (planets orbiting other stars) have many characteristics both similar to and different from our own solar system of planets orbiting the sun.
Goal
Students will conduct a series of inquiries about the nature of observed extrasolar planets using the Exoplanets Data Explorer.
Tasks
(Record your lab partners' names on your worksheet.)
1. Exploration
Consider the research question, "How are characteristics of solar planets distributed?" A histogram is a bar chart showing the number of objects in a particular category. Use the "Solar System Data Table" below (where the semi-major axis (which is approximately the average orbital distance) is measured in astronomical units (AU)) and sketch histograms (with a vertical scale for the bars).
Solar System Data Table| |
Planet: | Mass
(MEarth): | Mass
(MJupiter): | Period
(Years): | Period
(Days): | Semi-Major Axis
(AU): |
| | Mercury | 0.06 | 0.0002 | 0.24 | 88 | 0.39 |
| | Venus | 0.82 | 0.003 | 0.62 | 226 | 0.72 |
| | Earth | 1.00 | 0.003 | 1.00 | 365 | 1.00 |
| | Mars | 0.11 | 0.0003 | 1.88 | 687 | 1.52 |
| | Jupiter | 318 | 1.00 | 11.86 | 4,328 | 5.20 |
| | Saturn | 95.2 | 0.299 | 29.5 | 10,775 | 9.54 |
| | Uranus | 14.5 | 0.046 | 84.0 | 30,681 | 19.2 |
| | Neptune | 17.1 | 0.054 | 165 | 60,266 | 30.1 |
- Distribution of Orbital Distance Histogram
| Categories: | (1) Closer than Earth's Orbital Distance
(2) At or Farther than Earth's Orbital Distance |
6 |
5 |
4 |
Number of Planets: 3 |
2 |
1 |
0 |——————————|——————————
(1) (2)
- Distribution of Masses Histogram
| Categories: | (1) Less than Earth's Mass
(2) At or Greater than Earth's Mass |
6 |
5 |
4 |
Number of Planets: 3 |
2 |
1 |
0 |——————————|——————————
(1) (2)
- Distribution of Orbital Periods Histogram
| Categories: | (1) Less than Earth's Period
(2) From Earth's Period to Less than Jupiter's Period
(3) At or Greater than Jupiter's Period |
6 |
5 |
4 |
Number of Planets: 3 |
2 |
1 |
0 |——————————|——————————|——————————
(1) (2) (3)
Consider the research question, "What characteristics of solar planets are correlated with orbital distances?" A scatter plot is a graph of dots showing how two characteristics, or variables, are related. Use the "Solar System Data Table" above and graph these scatter plots.
- Distance vs. Period for Terrestrial Planets
y-axis: Orbital Distance (in AU)
x-axis: Orbital Period (in years)
4.0 |
|
3.0 |
|
2.0 |
Distance (AU): |
1.0 |
0.5 |
0 |—————|—————|—————|—————|—————|—————
0 1 2 3 4 5
Period (years)
- Distance vs. Period for Jovian Planets
y-axis: Orbital Distance (in AU)
x-axis: Orbital Period (in years)
40 |
|
30 |
|
20 |
Distance (AU): |
10 |
5 |
0 |—————|—————|—————|—————|—————|—————
0 50 100 150 200 250
Period (years)
- Distance vs. Mass for All Solar System Planets
y-axis: Orbital Distance (in AU)
x-axis: Mass (in MEarth units)
40 |
|
30 |
|
20 |
Distance (AU): |
10 |
5 |
0 |—————|—————|—————|—————|—————|—————
0 50 100 150 200 250
Mass (M_Earth)
Consider the research question, "Which characteristics of extrasolar planets are most highly correlated with distance?" The concept of correlation is the idea that two characteristics are related to one another. (Important note: correlation is not the same as cause-and-effect.)
- One of the two scatter plots below is "Human Intelligence versus Height," and the other is "Human Weight versus Height." In the space below, explain your reasoning why which scatter plot is which.
|x x | xx
| x xx | x
| x x | xx x
? |x x x ? | x
|x x | xx x
| xx x | x x
|____________ |____________
Height Height
Explanation: ___________.
- Based on your work above on analyzing the planets of our solar system, which variable, period or mass, seems to be most highly correlated with distance? Explain your reasoning, referring to the appropriate scatter plot(s) to illustrate your answer.
Explanation: ___________.
2. Does Evidence Match a Given Conclusion?
Access the Exoplanets Data Explorer at http://exoplanets.org and click on "Table" to see a table of confirmed extrasolar planets and their associated data. Click on the large "+" button in the upper right-hand corner, and select "Date." Then click on the new "Date" column heading to sort the extrasolar planets with the most recent at the top. Choose the most recent extrasolar planet with complete information listed in the table to the answer the following questions, and record data about it here.
Planet: __________.
Mass: __________ MJupiter.
Semi-Major Axis: __________ AU.
Orbital Period: __________ days (or years).
- Is this planet more massive than Earth? If so, how many times more massive?
More or less massive than Earth? __________.
If more massive, how many times more massive? __________×.
- Is this planet more massive than Jupiter? If so, how many times more massive?
More or less massive than Jupiter? __________.
If more massive, how many times more massive? __________×.
Select "Plots > Histogram Plot, and select "Advanced" mode ("Visual Style > Bars" should already be selected). Choose the "Data" to be "Semi-Major Axis" with minimum distance = 0 AU and maximum distance = 10 AU. Then adjust the "# Bins" = 10. You should be able to read the number of planets in each bar by placing the cursor over the top of the bar. (Earth orbits the sun at a distance of 1 AU, and Jupiter orbits at about 5 AU.)
- Answer the following questions about your histogram:
Total number of extrasolar planets in data set: __________.
(This is the "#" value on the graph settings window)
Number with orbits larger than Jupiter: __________.
Percentage with orbits larger than Jupiter: __________.
Number with orbits smaller than Earth: __________.
Percentage with orbits smaller than Earth: __________.
Select "Plots > Histogram Plot, and select "Advanced" mode ("Visual Style > Bars" should already be selected). Choose the "Data" to be "Orbital Period" with minimum period = 0 days and maximum period = 900 days. Then adjust the "# Bins" = 18. You should be able to read the number of planets in each bar by placing the cursor over the top of the bar. (Earth orbits the sun once every 365 days, and Jupiter orbits once about every 4,300 days.)
- Answer the following questions about your histogram:
Total number of extrasolar planets in data set: __________.
(This is the "#" value on the graph settings window)
Number with orbits most similar to Mercury: __________.
Number with orbits most similar to Venus: __________.
Number with orbits most similar to Earth: __________.
Number with orbits most similar to Mars: __________.
Number with orbits most similar to Jupiter: __________.
(You may need to change the minimum/maximum period settings.)
Consider the research question, "How long do extrasolar planets take to orbit their star?" If a student proposed a generalization that "Most extrasolar planets discovered take about the same length of time to orbit their star as Earth takes to orbit the sun," would you agree or disagree with this generalization based on the evidence you collected by looking at the range of possible orbital periods? Explain your reasoning and describe specific evidence either from the above questions or from evidence you yourself generate using Exoplanets Data Explorer(*).
3. What Conclusions Can You Draw From This Evidence?
What conclusions and generalizations can you make from the data organized using a scatter plot in terms of "What range of planet masses and range of star masses are observed? How are planet masses and star masses correlated (if at all)?"
For your evidence, slect "Plots > Scatter Plot", and select "Advanced" mode. Choose the "Data > X" to be "Mass of Star," and the "Data > Y" to be "Msin(i)." (Msin(i) is the minimum estimated mass of a planet.) If the data points seem to be too concentrated in a certain region of the scatter plot, then select the "Log" checkbox for both axes in order to rescale the axes and "uncrowd" the data points. (Utilize this feature whenever necessary for other scatter plots.)
Explain your evidence-based conclusions, with sketches if necessary, to support your reasoning(*).
4. What Evidence Do You Need to Pursue?
Describe precisely what evidence you would need to collect in order to answer the research question, "If an extrasolar planet was discovered to have an orbital period of 21 days, what would you predict its semi-major axis orbital distance to be using a scatter plot?" (This time the orbital period is the "independent" or x-axis variable, and the semi-major axis of the planet's orbit is the "dependent" or y-axis variable.) You do not need to actually carry out the procedure you've written (but it would be instructive to actually display this scatter plot).
Create a detailed, step-by-step description of evidence that needs to be collected and a complete explanation of how this could be done--not just "make a scatter plot and look where 21 days is on it," but exactly what would someone need to do, step-by-step, to accomplish this. You might include a table and sketches--the goal is to be precise and detailed enough that someone else could follow your procedure(*).
5. Formulate a Question, Pursue Evidence, and Justify Your Conclusion
Design an answerable research question (*.html), propose a plan to pursue evidence, collect data, and create an evidence-based conclusion about an aspect that you have not completed before. (Have your instructor approve your whiteboard research question before proceeding further.)
Research report summary on whiteboards(*), to be worked on and presented as a group, should include:- Specific research question.
- Step-by-step procedure to collect evidence.
- Data table and/or results.
- Evidence-based conclusion statement.
At the end, check over your research by answering the assessment questions about your own project.
Assessment of Your Research Report
- Step-By-Step Procedure to Collect Evidence:
Was the plan you used going to yield the necessary evidence needed to fully answer the listed research question? If "yes," then merely state so. If "maybe" or "no," give a detailed explanation.
- Data Table and/or Results:
Has enough evidence been collected for this specific research question? If "yes," then merely state so. If "maybe" or "no," give a detailed explanation.
- Evidence-Based Conclusion Statement:
- In your conclusion, have you claimed more than the evidence supports? If "no," then merely state so. If "yes" or "maybe," give a detailed explanation.
- Have assumptions impacted your results? If "no," then merely state so. If "yes" or "maybe," give a detailed explanation.
- Does your conclusion directly answer the original research question? If "yes," then merely state so. If "maybe" or "no," give a detailed explanation.
Preparation/Reflection Points
1.0 = Pre-lab reading assignment
1.0 = Current events quiz
1.0 = Post-lab reflection assignment
Group Work Points(*)
Documentation (Tasks 1-4, graded from randomly selected group member)
2.0 = exploration complete and reasoning correct
1.5 = minor problem with exploration or reasoning
1.0 = minor problems with both exploration and reasoning
0.5 = problematic exploration and reasoning
Poster/presentation (task 5)
2.0 = research report complete and competent presentation
1.5 = minor problem with research report or presentation
1.0 = minor problems with both research report and presentation
0.5 = problematic research report and presentation
(Backwards Folded Scaffolding laboratory used with permission from: Tim Slater, Stephanie Slater, Daniel J. Lyons, Engaging in Astronomical Inquiry, W.H. Freeman & Company, New York (2010), pp. 75-88; additional revisions to include use of the Exoplanets Data Explorer website contributed by Paul E. Robinson (private communication).)
|
