Big and Tall or Short and Small?
Credits: NASA, JPL-Caltech
This activity demonstrates how the radar beam of a large radio telescope dish on Earth provides information about an asteroid even though the asteroid looks like a dot of light.
The pins of the pin art frame are like the scans of the radar beam. You can't see much of the asteroid itself, but by pinging it with radar, you can determine its shape and size.
Scientists measure the timing of the return beam to the telescope to reveal this information. Radar observations have revealed new moons of asteroids that were not observable by optical telescopes.
Radiotelescope observations helped asteroid Bennu zoom to the top of the OSIRIS-REx list because they revealed a perfect shape for our studies!
You will need
- Pin art frame, found at toy stores and department stores. One frame is okay, or use tape to attach 2 or 4 frames together for easy comparison and to prevent peeking.
- Household objects with easy, identifiable shapes that will fit under the frame without being seen (plastic shapes, rock, key, pencil, etc.).
- For multiple frames, use a tray to hold the objects. Outline their shape with a marker for easy activity reset.
Credit: University of Arizona
How it works
- Start with the pin art down on top of the collected objects.
- Explain to the observer that the individual pins represent the radar beam of a big radiotelescope like the one at Arecibe, Puerto Rico.
- Ask the observer to identify the shapes revealed by the pinging of the radar beam.
- Next, ask the observer to describe the properties of the object (color, material, composition, height, etc.) This cannot be done without peeking.
- Lift up the pin art frame to reveal the objects. Explain that this type of observation can only provide certain information. Much more is needed to learn all about asteroids.
Extra hints or suggestions
Some observers mistake the color of the pins for color of the object. Compare the activity to the game Battleship where the player "pings" the ocean until they get a "hit" on a ship and try to ascertain its shape and size. For a more challenging activity, layer objects with different shapes and try to describe them.
This is a radar "image" and shape model of asteroid Bennu, the target of the OSIRIS-REx mission. (Credit: Arecibo Radio Telescope and Goldstone Apple Valley Radio Telescope)
This activity is courtesy of the University of Arizona and the OSIRIS-REx Ambassadors program.