Exoplanet in a box

This hands-on activity on the transit method of exoplanet detection is designed to foster inquiry-based learning over four 50-minute sessions, allowing students to engage with the scientific process through active exploration and questioning.
In the first session, students will be introduced to the fundamental concepts of exoplanets and the transit method, where they will formulate their own research questions and hypotheses, driving the inquiry process forward. The second and third sessions focus on student-led experimentation, where they will model transit events using their cell-phones/tablets and inexpensive material. The students will explore how changes in some planetary parameters (size, distance, atmosphere, transit time (period, velocity, etc) affect light curves. By testing their own hypotheses, students take ownership of their learning and discover scientific principles through exploration. The fourth and final session will focus on data analysis and reflection, encouraging students to interpret their results, reassess their initial hypotheses, and present their conclusions to the class. This inquiry-based approach not only helps students understand the transit method but also cultivates critical thinking, problem-solving, and scientific communication skills. Teachers will facilitate this process, guiding students through each phase while promoting curiosity and self-directed discovery.

Session 1: Introduction to Exoplanets and the Transit Method (50 min)

Objective: Students will understand the significance of exoplanet research and the basics of the transit method for detecting exoplanets.

Warm-Up Discussion: The Purpose of Exoplanet Research

Start with open-ended questions to stimulate discussion:

• Why do you think scientists are so interested in finding planets outside our solar system?
• What do you think we could learn by studying planets orbiting other stars?
• How might finding an exoplanet that resembles Earth change the way we think about our own planet?
• Do you think it’s possible to find life on planets outside our solar system? Why or why not?
• What do you think would make a planet suitable for supporting life, and why is its distance from its star important?
• How do you think astronomers determine which exoplanets might be in the 'habitable zone' around their stars, and why is finding these planets so crucial?
• How do you think discovering more exoplanets could help us better understand our place in the universe?

Facilitate a class discussion to explore these questions, helping students connect their curiosity about space with the goals of exoplanet research. Mark on the board keywords pertaining to this hands-on investigation.

Introduction to the Transit Method

Question for small group discussion :

• What do you think are the biggest challenges astronomers face when trying to detect planets so far away?
• Given that these planets are so far away and often too small to see directly, how do you think scientists might detect them?
• If we can’t see the planets directly, could observing the stars they orbit give us any clues? What might we look for in the stars’ behavior that could hint at the presence of a planet?
• Imagine you’re watching a star from far away. If a planet passed between the star and us, what might happen to the light we see from that star?

Hints from the teacher:

• Have you ever noticed what happens to the light from a lamp when something passes in front of it? How might this idea be useful when observing stars?
• If you were an astronomer trying to find planets around other stars, how might you detect them without being able to see them directly?

After the discussion, the teacher explains the basics of the transit method, including how it detects exoplanets by observing the periodic dimming of a star's light as a planet passes in front of it (10 min)

Use diagrams and examples of light curves to illustrate how transits create observable signals.
(Examples: https://www.youtube.com/watch?v=mM3PYiyjn1o or https://astro.unl.edu/naap/esp/animations/transitSimulator.html)

Discover how to make light curves

Let students discover how to measure light curves using their cell phones or tablets (Apps: fizziq and phyphox ). Let the students install these applications and discover by themselves what they could measure with these apps and which sensor will they be using to measure the change in luminosity.
Note that the instrument that works best is Luxmeter in the app FIZZIQ, using Instrument Spot luminance.

Formulate Research Questions and Hypotheses

Guide students in developing their own research questions related to the transit method. (Student will use the scientific method handout)

Help students formulate hypotheses based on these questions.

Preview of Upcoming Activities

Briefly outline what will be covered in the next session, including hands-on modeling and simulation of transit events.

Explain how their hypotheses will guide these experiments and what they will need to do.

Session 2: Building the transit simulator (50 min)

Objective: Students will build their transit simulator and understand how to use it

Experiment Setup and Overview

The students will build the card box represented in Figure 2 to simulate the transit of an exoplanet.

Figure 2. A representation of the transit simulator.

To create the box: On one side (position a in Figure 2) make a hole in the box and glue a plastic cup to represent the star. Students will then position a light source, such as a cell phone (also see Image 3c) or a lamp, at the opening of the cup to simulate the star’s light.

On the opposite side of the box (position b in Figure 2), students will create a hole to position a smartphone to collect light coming from the light source (the star).

On the top of the box (position c in Figure 2), they will create three parallel slits at varying distances from the light source, to represent the orbits of exoplanets orbiting the star at different distances.

Figure 3. Building the box. Image 3a- cardboard box from above; Image 3b- the inside of the cardboard box, with the opening for the light source; Image 3c- a mobile phone used as a light source.

To create the exoplanets: the BBQ sticks serve as holders for small clay balls or disks of various sizes to simulate exoplanets (Image 4a). Students should ensure that the 'exoplanet' moves in front of the star, passing directly through the center of the light source (Image 4b). A blue mark on each stick can help indicate the right distance from the center of the light source (the cup) to the top of the slit.
When using disks to represent exoplanets, students should make sure the disks are not tilted and are facing the light source to present their maximum area. They can control this by aligning the disks with a parallel flat surface at the opposite side of the stick and maintaining the sticks vertically (Image 4b and 4c).
ADDITIONAL: Students may also explore the effect of having the exoplanet pass above or below the central line, this will depend on their inquiry.

Figure 4: Building the exoplanets. Image 4a- Holders simulating the exoplanets. Image 4b- ensuring that the exoplanet passes in front of the star. Image 4c- maintaining the exoplanet holders vertical.

To make exoplanets' atmospheres: To simulate the effect of the atmosphere of an exoplanet on the light curve, students can measure the light curve without atmosphere and with atmosphere putting a transparent film on the exoplanet (in Figure 5, the red disk is a transparent film).

Figure 5: Exoplanets with simulated atmospheres

To measure the light curve: To measure the light curve, students will install the application fizziq on their cell phones or tablets. They will use the instrument “Luxmeter” and measure with the sub-instrument “Average luminance”. Students should always calibrate before recording the data (Image 6). Examples of light curves are shown in the images below.

Figure 6: measuring the light curve using Fizziq with a smartphone. Image 6a- calibration; Image 6b, 6c, 6d: measured lightcurves.

Session 3: Modeling and Simulating Transit Events (50 min)

Objective: Students will manipulate their models to simulate transits, experimenting with different parameters to observe their effects. They will use the Experiment-form.doc attachey to document their approach to the scientific method.

Hands-On Activity: Modeling Transit Events

Students will work in small groups to build their models, adjusting parameters like planet size, distance from the star, atmosphere, etc. to observe and systematically measure how these changes affect the light curve.

Data Collection

Students record the results of their experiments in tables in the scientific method form (e.g., transit depth, duration, etc, based on changing parameters).

Encourage them to analyze the immediate effects and discuss their findings in groups.

Session 4: Data Analysis, Conclusion, and Communication (50 min)

Objective: Students will analyze the collected data, draw conclusions, and present their findings to the class. (They need to report their data and analysis in the scientific method form.)

Analyzing Data

Students analyze the data from the previous session, identifying patterns or trends (e.g., larger planets create deeper transits, compare exoplanet areas to luminosity reduction ratios, do the same with distances, simulated atmospheres, etc.).

Conclusion and Reflection

Have students reflect on whether their data supports their original hypothesis.

They should write a brief conclusion based on their results.

Presentations by groups

Each group presents their findings, discussing their hypothesis, results, and any challenges they encountered during the experiment.

Wrap-Up and Feedback

Summarize key takeaways from the workshop.

Allow time for questions, clarifications, and feedback on what they learned and how they can apply these methods to real-world astronomy.

Here are examples of reflection and feedback questions by the teacher:

Reflection Questions:

• What did you find most interesting or surprising about the transit method you learned?
• How has your understanding of exoplanets evolved during this workshop?
• What challenges did you encounter while modeling and simulating transits? How did you overcome them?
• How did the results of your experiments confirm or alter your initial hypotheses?
• How do you think the concepts you learned today could be applied to real-world astronomical research?

Feedback Questions:

• What did you like about the activities in this workshop? Are there any aspects you would have liked to explore further?
• Were there any parts of the workshop that you found less clear or difficult to follow? How could these be improved?
• Do you have any suggestions for making this workshop more interactive or engaging?
• How would you assess your ability to communicate your scientific findings after this workshop? What skills would you like to continue developing?
• Is there anything additional you would have liked to learn during this workshop?