Overall intention: Develop a greater understanding of habitable zone characteristics associated with different planetary systems.  Further, this will help improve an understanding of the potential existence of life elsewhere (one of the last topics of this course).  After completing this exercise, you should be able to describe the necessary ingredients for life to flourish on another Earth-like planet elsewhere in the universe.

Getting Started with Linking Lab: Habitable Zones

1. Open the Student Guide file (DOCX) and print a working copy:   Habitable Zones Student Guide DOCX

2. Follow the steps outlined in the Student Guide (the document downloaded in step 1 above).

3. Record your answers on the working copy.

4. If needed, scan your work to a DOC or DOCX file

5. Submit (attach) to the lab 4 submission area in session 16

Resources that are mentioned in the student guide are below. Most are interactive diagrams with useful information.

• Life in the Universe - http://astro.unl.edu/naap/habitablezones/life.html
• Circumstellar Habitable Zones - http://astro.unl.edu/naap/habitablezones/chz.html
• Galactic Habitable Zones - http://astro.unl.edu/naap/habitablezones/ghz.html
• Circumstellar Habitable Zone Simulator -

http://astro.unl.edu/naap/habitablezones/animations/stellarHabitableZone.html

• Milky Way Habitability Explorer -

http://astro.unl.edu/naap/habitablezones/animations/milkyWayHabitability.html

QUESTIONS -

Question 1: Drag the planet to the inner boundary of the CHZ and note this distance from the Sun. Then drag it to the outer boundary and note this value. Lastly, take the difference of these two figures to calculate the "width" of the sun's primordial CHZ.

Question 2: Let's explore the width of the CHZ for other stars. Complete the table below for stars with a variety of masses.

Question 3: Using the table above, what general conclusion can be made regarding the location of the CHZ for different types of stars?

Question 4: Using the table above, what general conclusion can be made regarding the width of the CHZ for different types of stars?

Question 5: Zoom out so that you can compare this planet to those in our solar system (you can click-hold-drag to change the scale). Is this extra solar planet like any in our solar system? In what ways is it similar or different?

Question 6: Select the system HD 93083. Note that planet b is in this star's CHZ. Now in fact this planet has a mass of at least 0.37 Jupiter masses. Is this planet a likely candidate to have life like that on Earth? Why or why not?

Question 7: Note that Jupiter's moon Europa is covered in water ice. What would Europa be like if it orbited HD93083b?

Question 8: Return to the none selected mode and configure the simulator for Earth. Note that immediately after our Sun formed Earth was in the middle of the CHZ. Drag the timeline cursor forward and note how the CHZ moves outward as the Sun gets brighter. Stop the time cursor at 4.6 billion years to represent the present age of our solar system. Based on this simulation, how much longer will Earth be in the CHZ?

Question 9: What is the total lifetime of the Sun (up to the point when it becomes a white dwarf and no longer supports fusion)?

Question 10: What happens to Earth at this time in the simulator?

Question 11: It took approximately 4 billion years for complex life to appear on Earth. In which of the systems above would that be possible? What can you conclude about a star's mass and the likeliood of it harboring complex life?

Question 12: Notice that the planet is shown with a dashed line through its middle. What has happened is that the planet is so close to its star that is has become tidally locked due to gravitational interactions. This is analogous to Earth's moon which always presents the same side towards Earth. For a planet orbiting a star, this means one side would get very hot and the other side would get very cold. (However, a thick atmosphere could theoretically spread the heat around the planet as happens on Venus. In answering the following questions, please put aside this possibility.)

Question 13: What would happen to Earth's water if it were suddenly to become tidally locked to the Sun? What would this mean for life on Earth?

Question 14: Complete the table below by resetting the simulator, setting the initial star mass to the value in the table, and positioning the planet in the middle of the CHZ at time zero. Record whether or not the planet is tidally locked at this time. If tidal locking reduces the likelihood of life evolving on a planet, which system in the table is least conducive towards life?

Question 15: What factor influences the rate of planet formation? How does this vary as a function of a star system's distance from the center of the Milky Way?

Question 16: What sort of events can wipe out life on a planet? How does the likelihood of extinction for life vary depending upon a star system's distance from the center of the Milky Way?

Question 17: Present a version of the Goldilock's Hypothesis for the GHZ that is similar in character to that which we stated for the CHZ earlier.

Attachment:- Assignment.rar