Part 2: Build Your Own Planet
Lesson 1: The Sun’s Habitable Zone
Time: approximately 40 - 50 minutes
Materials: Text: Lesson 1 – Determining Our Sun’s Habitable Zone (from web site - 1 per group)
Habitable Zone Table (included with students’ Lesson 1 - 1 per group)
Overview
This lesson introduces the Planet Temperature Calculator, which determines the approximate average surface temperature of a planet based on values for different physical properties entered by the user. Students will use this program to find out how the distance from the Sun affects the Earth’s average surface temperature. Students then graph the effects of changes in distance on average surface temperatures using Microsoft Excel. The graph is relatively straightforward, and students without access to Excel can make the graphs by hand.
Purpose
The purpose of this lesson is to introduce the idea of the “habitable zone.” The habitable zone is the distance from a star that an object needs to be in order to maintain a surface temperature that will allow water on the surface to stay in a liquid state. If a planet is too close to a star the surface will get too hot and water will boil away. If it is too far away it will get too cold and water will freeze.
Standards
A complete list of the standards covered by this lesson is included in Appendix A at the end of the lesson.
Procedure
Students should get in their groups with their folders. Each group will need access to the Planet Temperature Calculator, which is available over the World Wide Web at: As a class review the introduction to the lesson:
In this lesson we will determine our Sun’s “habitable zone.” The habitable zone is the distance from the Sun that the Earth can be and still support life on its surface. Remember that all life that we know of requires liquid water to survive. Therefore, we can define our habitable zone as the range of distances from the Sun where the Earth’s average surface temperature is greater than 0ºC (the melting point of water) but less than 100ºC (the boiling point). To find out where this area is we will use the Planet Temperature Calculator. This program figures out the average surface temperature of a planet based on information about that planet that you enter.
The Planet Temperature Calculator looks at the MASS of the star that your planet is orbiting, the DISTANCE from that star, the BOND ALBEDO (al-BEE-do) of the planet and the GREENHOUSE EFFECT of the planet’s atmosphere. In the last lesson we said that increasing the MASS of a star increases the energy that it gives off (and reduces its life span). In later lessons we will look at the effects of BOND ALBEDO and GREENHOUSE EFFECT on temperature. Today we will see how the DISTANCE from the nearest star affects the temperature. We will enter Earth-like values for MASS, BOND ALBEDO and GREENHOUSE EFFECT, enter different values for DISTANCE, and record our results.
The Planet Temperature Calculator is easy to use. Groups should enter different values for DISTANCE and record the calculated temperatures on their Habitable Zone Tables.
1) Open the planet temperature program:
2) Read the information on this screen and then click on the “continue” button. This will bring you to the MASS screen. Read the information about MASS and then , in the white box below the text, enter the number 1 and click the “next” button next to the box.
3) This will bring you to the DISTANCE screen. Read the information about DISTANCE, enter the number 1 in the white box, and click the “next” button.
4) This will bring you to the BOND ALBEDO screen. Read about BOND ALBEDO, enter the number 29, and click the “next” button.
5) You should be at the GREENHOUSE EFFECT screen now. Read about the GREENHOUSE EFFECT and enter the number 1 in the box. Then click the “next” button.
6) This brings you to the “REVIEW” page. You can change any of the values that you entered on this screen. Don’t make any changes yet, just click on the button marked “calculate” in the bottom right corner of the screen.
7) This page tells you what the average surface temperature of your planet is based on the numbers that you entered. If you entered the numbers correctly you will see that the Earth has an average surface temperature of 15 ºC or 59 ºF. You will also see, in the white box toward the center of the screen, that our Sun has a life cycle of 10 billion years. That means that our Sun has enough fuel to last 10 billion years. Since the Sun is around 4.7 billion years old, that means it will last for another 5.3 billion years before it uses up all its nuclear fuel and dies in a violent explosion.
Fill out the Habitable Zone Table.
8) Click the “return” button to go back to the REVIEW screen. Do not change the values for MASS, BOND ALBEDO or GREENHOUSE EFFECT. Use the Habitable Zone Table to find out what values to enter for DISTANCE. Start by entering 0.1 for DISTANCE and click the CALCULATE button. Record the SURFACE TEMPERATURE in degrees Celsius on the table in the box next to “0.1” Be sure to record the temperature in degrees Celsius. This is the number in the middle of the three stacked boxes.
9) Click the RETURN button. Enter 0.2 for DISTANCE and click the CALCULATE button. Record the SURFACE TEMPERATURE in degrees Celsius on the table in the box next to “0.2” Click the RETURN button.
10) Continue finding and recording the SURFACE TEMPERATURE for the rest of the numbers on the table.
Next students will graph their findings in Microsoft Excel. The X-axis will display the distance from the Sun, and the Y-axis will represent the average surface temperature.
Making graphs in Microsoft Excel is generally very easy, but some procedures, like setting the values of your X-axis, are much less obvious than they could be. Teachers might want to work through this next section beforehand if possible.
Make a chart in Microsoft Excel.
11) Start Microsoft Excel. Open a new file. In column A, enter “0.1” in space A1, “0.2” in space A2, etc., down to “1.3” in space A13. In column B, enter the temperatures from the Habitable Zone Table. Enter the first temperature in space B1, the second temperature in space B2, etc.
12) On the menu bar, click on Insert>Chart (or click on the Chart icon). This opens up the Chart Wizard box.
13) Select the Line chart and click Next.
14) Click on the DataRange tab at the top of the Chart Wizard and then click on the little data icon on the far right side of the white box in the middle of the Wizard, next to the space marked DataRange. Click and drag your cursor over spaces B1 through B13, and hit Enter. (Do not click Next yet.)
15) Now click on the Series tab. At the bottom of the box is a space marked Category (X) axis labels. Click on the data icon to the right of this space. Click and drag your cursor over spaces A1 through A13, and hit Enter. Click Next.
16) Click on the Titles tab. For the Chart title: type the name of your group and then “The Sun’s Habitable Zone.” For Category (X) axis: type “Distance in Astronomical Units (AU).” For Value (Y) axis: type “Temperature in Degrees Celsius.” (Do not click Next yet.)
17) Click on the Gridlines tab. For Category (X) axis select “Minor gridlines.” Check to make sure the “Major gridlines” is selected for Value (Y) axis. (Do not click Next yet.)
18) Click on the legend tab. De-select “Show legend” by clicking on the box next to “Show legend” so that the checkmark disappears. Click on Next.
19) For Place chart: select “As new sheet.” Click Finish. Print your chart.
20) At Earth’s normal atmospheric pressure, water freezes at 0ºCelsius (C) and boils at 100ºC. The Sun’s habitable zone is the distance from the Sun where a planet’s average surface temperature is between 0ºC & 100ºC. On your chart, find the point where the line of the graph crosses the horizontal line for 100ºC, and then check how far out on the X axis (Distance in AU) this is. This is the inner limit of the Sun’s habitable zone. Next find the point where the line of the graph crosses the horizontal line for 0ºC, then check how far out on the X axis this point is. This is the outer limit.
21) Our Sun’s habitable zone inner limit is ______AU. If the Earth was any closer to the Sun than this the liquid water on its surface would boil away.
The Sun’s habitable zone outer limit is ______AU. If the Earth was any farther away from the Sun than this the liquid water on its surface would freeze.
If the Earth was outside of this habitable zone, chances are that life as we know it would not be able to survive at the surface.
Groups should keep their graphs, tables and worksheets in the group folders.
Appendix A
Standards Addressed
Benchmarks (Grades 3 through 5)
2A – Patterns and Relationships
Mathematical ideas can be represented concretely, graphically, and symbolically.
2C – Mathematical Inquiry
Numbers and shapes-and operations on them-help to describe and predict things about the world around us.
4D – Structure of Matter
Heating and cooling cause changes in the properties of materials. Many kinds of changes occur faster under hotter conditions.
5D – Interdependence of Life
For any particular environment, some kinds of plants and animals survive well, some survive less well, and some cannot survive at all.
9B – Symbolic Relationship
Tables and graphs can show how values of one quantity are related to values of another.
11B – Models
Seeing how a model works after changes are made to it may suggest how the real thing would work if the same were done to it.
11C – Constancy and Change
Things change in steady, repetitive, or irregular ways-or sometimes in more than one way at the same time. Often the best way to tell which kinds of change are happening is to make a table or graph of measurements.
12A – Values and Attitudes
Keep records of their investigations and observations and not change the records later.
12D – Communication Skills
Use numerical data in describing and comparing objects and events.
Benchmarks (Grades 6 through 8)
2B – Mathematics, Science and Technology
Mathematics is helpful in almost every kind of human endeavor-from laying bricks to prescribing medicine or drawing a face. In particular, mathematics has contributed to progress in science and technology for thousands of years and still continues to do so.
4E – Energy Transformation
Most of what goes on in the universe-from exploding stars and biological growth to the operation of machines and the motion of people-involves some form of energy being transformed into another. Energy in the form of heat is almost always one of the products of an energy transformation.
Heat can be transferred through materials by the collisions of atoms or across space by radiation. If the material is fluid, currents will be set up in it that aid the transfer of heat.
9B – Symbolic Relationship
Graphs can show a variety of possible relationships between two variables. As one variable increases uniformly, the other may do one of the following: increase or decrease steadily, increase or decrease faster and faster, get closer and closer to some limiting value, reach some intermediate maximum or minimum, alternately increase and decrease indefinitely, increase or decrease in steps, or do something different from any of these.
11B – Models
Models are often used to think about processes that happen too slowly, too quickly, or on too small a scale to observe directly, or that are too vast to be changed deliberately, or that are potentially dangerous.
Mathematical models can be displayed on a computer and then modified to see what happens.
11D – Scale
As the complexity of any system increases, gaining an understanding of it depends increasingly on summaries, such as averages and ranges, and on descriptions of typical examples of that system.
12D – Communication Skills
Organize information in simple tables and graphs and identify relationships they reveal.
Read simple tables and graphs produced by others and describe in words what they show.
Benchmarks (Grades 9 through 12)
1B – Scientific Inquiry
Sometimes, scientists can control conditions in order to obtain evidence. When that is not possible for practical or ethical reasons, they try to observe as wide a range of natural occurrences as possible to be able to discern patterns.
2B – Mathematics, Science and Technology
Mathematical modeling aids in technological design by simulating how a proposed system would theoretically behave.
Mathematics provides a precise language for science and technology-to describe objects and events, to characterize relationships between variables, and to argue logically.
4A – The Universe
Mathematical models and computer simulations are used in studying evidence from many sources in order to form a scientific account of the universe.
4B – The Earth
Life is adapted to conditions on the earth, including the force of gravity that enables the planet to retain an adequate atmosphere, and an intensity of radiation from the sun that allows water to cycle between liquid and vapor.
9B – Symbolic Relationship
Any mathematical model, graphic or algebraic, is limited in how well it can represent how the world works. The usefulness of a mathematical model for predicting may be limited by uncertainties in measurements, by neglect of some important influences, or by requiring too much computation.
Tables, graphs, and symbols are alternative ways of representing data and relationships that can be translated from one to another.
11B – Models
The basic idea of mathematical modeling is to find a mathematical relationship that behaves in the same ways as the objects or processes under investigation. A mathematical model may give insight about how something really works or may fit observations very well without any intuitive meaning.
Computers have greatly improved the power and use of mathematical models by performing computations that are very long, very complicated, or repetitive. Therefore computers can show the consequences of applying complex rules or of changing the rules. The graphic capabilities of computers make them useful in the design and testing of devices and structures and in the simulation of complicated processes.
11C – Constancy and Change
Graphs and equations are useful (and often equivalent) ways for depicting and analyzing patterns of change.
12B – Computation and Estimation
Use computer spreadsheet, graphing, and database programs to assist in quantitative analysis.
12C – Manipulation and Observation
Learn quickly the proper use of new instruments by following instructions in manuals or by taking instructions from an experienced user.
Use computers for producing tables and graphs and for making spreadsheet calculations.
12E – Critical-Response Skills
Check graphs to see that they do not misrepresent results by using inappropriate scales or by failing to specify the axes clearly.
National Standards (Grades 5-8)
Transfer of Energy
The sun is a major source of energy for changes on the earth's surface. The sun loses energy by emitting light. A tiny fraction of that light reaches the earth, transferring energy from the sun to the earth. The sun's energy arrives as light with a range of wavelengths, consisting of visible light, infrared, and ultraviolet radiation.
Earth in the Solar System
The earth is the third planet from the sun in a system that includes the moon, the sun, eight other planets and their moons, and smaller objects, such as asteroids and comets. The sun, an average star, is the central and largest body in the solar system.
National Standards (Grades 9-12)
Understandings about Scientific Inquiry
Scientists rely on technology to enhance the gathering and manipulation of data. New techniques and tools provide new evidence to guide inquiry and new methods to gather data, thereby contributing to the advance of science. The accuracy and precision of the data, and therefore the quality of the exploration, depends on the technology used.
Matter, Energy, and Organization in Living Systems
The energy for life primarily derives from the sun. Plants capture energy by absorbing light and using it to form strong (covalent) chemical bonds between the atoms of carbon-containing (organic) molecules. These molecules can be used to assemble larger molecules with biological activity (including proteins, DNA, sugars, and fats). In addition, the energy stored in bonds between the atoms (chemical energy) can be used as sources of energy for life processes.
Energy in the Earth System
Earth systems have internal and external sources of energy, both of which create heat. The sun is the major external source of energy. Two primary sources of internal energy are the decay of radioactive isotopes and the gravitational energy from the earth's original formation.