OverviewIn this activity, students will learn the basic characteristics of a comet and older students will practice evaluation and improvement of their comet models. The importance of this activity is not the initial model or its exercise, but the fact that it will put students in the position of emulating a process that scientists and engineers follow on all missions.
ManagementWatch the "DIY Space: How to Make a Comet" video tutorial at the top of the page for instructions on making the comet.
The Deep Impact mission launched in 2004 and encountered Comet Tempel 1 on July 4th of 2005. Before launch, scientists and engineers used modeling to research and test some of their theories about comets. They also used modeling to find solutions to some of their mission challenges.
Modeling takes place throughout the life of a mission as challenges arise. Modeling is an important part of any space mission and begins earlier than most people think. Before any piece of hardware is built or software is designed -- in fact, before anyone begins to make calculations for the size and shape of the spacecraft -- intensive research must be done and certain questions must be asked.
- What do we want to find out?
- Where should we go in space to find this information?
- In the case of the Deep Impact mission, what do we know about Comet Tempel 1?
Since it isn't possible to visit Tempel 1 to get all the information we need in order to design a mission, scientists and engineers perform exercises to "model" the object they want to visit. They ask themselves questions like:
- What other comets do we have information on?
- What has that information told us?
- If we build a model for a comet we know better, will it tell us what we need to know about the one we will visit?
The Deep Impact mission used images of Halley's comet as well as images of comet Borrelly and Wild 2. Using what we know about those comets, and combining that information with images of Comet Tempel 1 taken from Earth, the Deep Impact team created models for researching the following challenges:
- How fast is our comet rotating and is that rotation slow enough to allow us to see the crater we make?
- When sunlight falls unevenly on the comet, can we design software that will help our impactor find the best lit area to target?
- Based on what we know about cometary dust environments, will our impactor and spacecraft arrive safely to impact? How large a dust particle can the spacecraft survive before the images they are collecting are blurred or the spacecraft themselves are damaged?
Making the comet
- Make a tiny hole in the Styrofoam ball so it can be mounted on the skewer (the fit of the skewer should be tight) or, if using a sheet of paper, mold it into the shape your team believes should represent your comet nucleus
- Mount the ball or molded paper on the skewer.
- Place the Mylar strips on top of the ball or paper nucleus so the two pieces cross each other in an "X" and the lengths of all sides of the strips hang down evenly. You can also use light ribbon.
- Attach the strips to the ball or paper with the a 5-inch strip of tape or narrow masking tape wrapped over the strips and around the circumference of the nucleus.
- With a marker pen, assign a "front" for your comet and represent it with the letter "H" for head. On the opposite side, mark the letter "T" for the comet tail.
Simulating the comet
- Use a hairdryer to simulate a portion of the sun's solar energy as it meets the comet. The heat from the sun warms the surface of the comet nucleus. This causes gas, ice, particles and rocky debris of various sizes to burst from the comet in all directions, created what's called a "coma" and the solar wind causes these substances to flow back behind the nucleus to form a "tail" behind the comet.
- Have someone be the sun and stand in place with the hairdryer. The hairdryer simulates the solar wind causing the comet "tail" to form and trail behind the comet.
- Aim the hairdryer at the comet and keep it trained on the comet as it approaches and as it moves away.
- Have a second person hold the comet by the stick and walk in an elliptical (elongated or oval) orbit around the sun (student holding the hairdryer). As the comet gets closer to the sun, the sun's solar influence affects the comet so that the gas and debris forms a tail that is pushed toward the back of the nucleus. This tail flows in opposition to the sun so that the nucleus is between the sun and the tail. As it travels away, the lost influence of the sun causes the tail to diminish, or in this case, fall. The solar wind from the sun, which is made of electrically-charged particles, uses electrostatic attraction and electrical transfer to form the comet's gas and debris into a tail.
- If you were building a model of a comet out of odds and ends around the house, what two characteristics about a comet would you choose to show and what materials would you find to build it?
- If you were designing a mission, how would you use your comet model to test some of your challenges and find solutions?
Use these questions for discussion or as an evaluation tool with your students.
- Where do comets come from?
- What are comets made of?
- How do they get from their origin to near Earth?
- What is inside them?
- Where are they now?
- How do you tell the difference between a comet and a shooting star?
- How many are there?
- What is the tail made of?
- Do they all travel the same direction?
- What makes them fly?
- Are they hot and burning?
- Is the tail dangerous?
- What is the life span for a comet?
- Is a comet a ball of gas?
- Is it ice?
- Is it a rock?
- Is it a ball of fire?
- Is it like a shooting star?
- What activates comets?
- Why was Halley's Comet so popular?
- Can they be re-routed?
- How close do they come to Earth?
- Do they have a head and a tail?
- Are they from deep in outer space?
- Are they from the black hole?
- What is "periodic"?
- What keeps them going? Do they have something like a jetpack?
- Why are new ones discovered?
- How do you distinguish one comet from another?
- Have students design their own comet models to explore some of the facts, theories and concepts about comet science. Have students bring materials from home and put students in teams to decide on a mission design, comet theory or comet question they would like to communicate. Students will design a model to communicate their question about the comet, build it and design a test to try to confirm their theories.