Download Planetary Transit Activity

Orbits Table Supplement—Draft Document Feb 2006
Planetary Transit Activity
Brief Summary
The Planet Transit Activity (PTA) is a removable attachment to the existing Orbits Table. A
new few props are included. The PTA device is a light bulb supported by a metal arm. The
metal arm holds the light bulb solidly in place over the center of the table. Wooden ball props
representing planets can be placed on various rings to illustrate planetary phenomena. The
PTA support arm contains a light sensor which in turn is attached to an existing laptop
computer. Computer software then creates a real time graph showing that the light received at
the sensor drops as simulated planets on the rings transits in front of the bulb.
Equipment Required & Operating tips
IMPORTANT SAFETY NOTE: The small props are a CHOKING HAZARD and must NEVER
be left out on the Orbits Table when it is unfacilitated.
The light bulb on the PTA can be turned on or off for different activities.
To get started, all you have to do is place the base of the PTA into the bin on the Orbits Table,
plug in the power cord and connect the USB cord that runs between the interface box and the
laptop computer.
Dimitri having fun with PTA
Jim removing PTA from
Orbits Table
PTA in place in storage
cradle
Main Teaching Points
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Phases of the planets
Elongations, oppositions, conjunctions and synodic periods of the planets
Transits of Venus and Mercury
Eclipses of the sun and moon
Discovery of exoplanets by the transit method
Graph reading
Light intensity units
Noise in scientific measurements
Educational Strategies
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The Planet Transit Activity is visually attractive.
The PTA in tour guide mode provides the facilitator with a half dozen concepts that the
projection on a flat surface cannot illustrate very well.
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It is very versatile in that it can be used SIMULTANEOUSLY with both younger children and
adults.
It upgrades the already popular Orbits Table to the level of a truly open inquiry interactive
exhibit.
The PTA also provides a venue for Project Curiosity’s exploratory activities.
Some Activities to Try:
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Play the role of discovery sparker by asking the key questions that a facilitator uses to take
someone through the Discovery Cycle:
1. Phases of planets
 Have visitors watch one planet prop as it makes a full orbit.
 Ask them to observe the illumination of the side of the planet facing them. What are these
phases? Does Venus have phases? What about Mars?
 Call up a website that shows pictures of Venus’ phases.
2. Illustrate elongations, oppositions, conjunctions and synodic periods of the planets, for example,
Venus has two conjunctions every 584 days.
3. Eclipses of the sun and moon.
 Turn on the light bulb.
 Stop the motion of the rings.
 Using one large and one small ball on a stick to illustrate the sun and moon, have visitor try to
illustrate a solar eclipse and lunar eclipse.
 Point out that the Seeing the Sun exhibit has a video clip of an actual solar eclipse.
4. How astronomers discover exoplanets
A. Discovering what the graph says.
 Illustrate how the light sensor works to create a real time graph of illumination versus time.
 Have a visitor put two large planet props on two different rings, one close to the sensor one far
from the sensor.
 Help the visitor discover that on the Orbits Table the sensor is measuring only angular size. Two
factors contribute to angular size: distance from the sensor and diameter of the planet. It would
also be possible to have two planets equal in all ways except reflectivity. Would having a white
planet make any difference? Why or why not?
 Have visitors repeat the experiment with two different sized planets. How does this affect the
graph?
 Have visitors observe that the inverted spikes on the graph are periodic and correspond to the
size and period of the planets on the rings.
b. A Game of Planetary Who Done it.
 Have visitors divert their eyes from the rings, and place two planets props on the rings.
 Have visitors look only at the graph and see if they can tell which combination of planets on the
rings created the graph. (This is just the situation astronomers are in)
Science Facts
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Scientists don’t use lux (the metric unit of light intensity) but watts/m2 a unit of energy flux.
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The actual time that an exoplanet takes to pass in front of its parent star is about half a day.