Teaching Resources / Exoplanets
Worksheet: Planet Hunting with TESS
This worksheet goes with the Transit Detective activity.
NamePartnerMy mystery star
Part A: Make a planet pass in front of a star
The lamp is a star, the foam ball is a planet, and the light sensor is the TESS telescope.
1. Predict. Sketch what you think the graph of brightness vs. time will look like as the ball passes in front of the lamp.
2. Predict, then observe. The big ball is twice as wide as the medium ball.
| My prediction | What we saw | |
|---|---|---|
| How many times deeper is the big ball's dip? | ||
| What changes when the ball moves twice as fast? | ||
| What changes when the ball crosses near the top edge of the lamp? |
3. Explain. Why is the big ball's dip so much deeper than you might expect? (Hint: think about area, not width.)
Part B: Transit Detective
Open Transit Detective. Do Star A together as a class, then your pair's mystery star. Fill in the rest of the table when the class shares results, or yourself if you have time.
| Star | Dips marked | Period (days) | Depth (%) | Star radius (R☉) | Planet radius (Earth radii) | Planet or impostor? |
|---|---|---|---|---|---|---|
| A | ||||||
| B | ||||||
| C | ||||||
| D | ||||||
| E | ||||||
| F |
Check the tool's math for Star A. The fraction of light blocked equals the planet's disk area divided by the star's disk area:
depth = (Rplanet / Rstar)2 ⇒ Rplanet = Rstar × √depth × 109
The 109 converts Sun radii into Earth radii. Write the depth as a decimal (1% = 0.01).
Planet radius = ______ × √______ × 109 = ______ Earth radii
Questions
1. How did you decide your period was correct? What did the folded plot look like when it was wrong?
2. Star C's dips are hard to see in the raw data but obvious after folding. Why does stacking many transits on top of each other help?
3. Star C's planet is about the size of Earth, yet TESS found it easily. What about Star C made that possible?
4. What clues told the class that Star F is not a planet? List at least two.
Part C: Real planet hunting
Go to Planet Hunters TESS on Zooniverse. Volunteers look for transits that computer searches can miss, and the science team follows up the best candidates. Do the short tutorial, then classify at least five.
| Light curves classified | Transits I marked | Describe the most interesting one |
|---|---|---|
What makes a real light curve harder to judge than the ones in Transit Detective?
Part D: Exit ticket
LHS 3844 b is about the size of Earth, and its dip is 0.4% deep. An identical planet passing in front of the Sun would make a dip of only about 0.008%. Why is the dip so much smaller?