Lesson 7 Lab - Habitable Zone Worksheet PDF

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Dec 6, 2023

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NAAP – Habitable Zones 1/7 Name: Exercises Lesson 7 Lab - Habitable Zones Please read through the background pages entitled Life, Circumstellar Habitable Zones, and The Galactic Habitable Zone before working on the exercises using simulations below. Circumstellar Zones Open the Circumstellar Zone Simulator . There are four main panels: • The top panel simulation displays a visualization of a star and its planets looking down onto the plane of the solar system. The habitable zone is displayed for the particular star being simulated. One can click and drag either toward the star or away from it to change the scale being displayed. • The General Settings panel provides two options for creating standards of reference in the top panel. • The Star and Planets Setting and Properties panel allows one to display our own star system, several known star systems, or create your own star-planet combinations in the none-selected mode. • The Timeline and Simulation Controls allows one to demonstrate the time evolution of the star system being displayed. The simulation begins with our Sun being displayed as it was when it formed and a terrestrial planet at the position of Earth. One can change the planet’s distance from the Sun either by dragging it or using the planet distance slider. Note that the appearance of the planet changes depending upon its location. It appears quite earth-like when inside the circumstellar habitable zone (hereafter CHZ). However, when it is dragged inside of the CHZ it becomes “desert-like” while outside it appears “frozen”. Question 1: (1 point) 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. CHZ Inner Boundary CHZ Outer Boundary Width of CHZ Question 2: (1 point) Let’s explore the width of the CHZ for other stars. Complete the table below for stars with a variety of masses. Star Mass (M ☉ ) Star Luminosity (L ☉ ) CHZ Inner Boundary (AU) CHZ Outer Boundary (AU) Width of CHZ (AU)

0.3 0.7 1.0 2.0 4.0 8.0 15.0 Question 3: (1 point) Using the table above, what general conclusion can be made regarding the location of the CHZ for different types of stars? Question 4: (1 point) Using the table above, what general conclusion can be made regarding the width of the CHZ for different types of stars? Exploring Other Systems Begin by selecting the system 51 Pegasi. This was the first planet discovered around a star using the radial velocity technique. This technique detects systematic shifts in the wavelengths of absorption lines in the star’s spectra over time due to the motion of the star around the star-planet center of mass. The planet orbiting 51 Pegasi has a mass of at least half Jupiter’s mass. Question 5: (1 point) 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 extrasolar planet like any in our solar system? In what ways is it similar or different?

Question 6: (1 point) 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: (1 point) Note that Jupiter’s moon Europa is covered in water ice. What would Europa be like if it orbited HD 93083b? Select the system Gliese 581. This system is notable for having some of the smallest and presumably earth-like planets yet discovered. Look especially at planets c and d which bracket the CHZ. In fact, there are researchers who believe that the CHZ of this star may include one or both of these planets. (Since there are several assumptions involved in the determination of the boundary of the CHZ, not all researchers agree where those limits should be drawn.) This system is the best candidate yet discovered for an earth-like planet near or in a CHZ. The Time Evolution of Circumstellar Habitable Zones We will now look at the evolution of star systems over time and investigate how that affects the circumstellar zone. We will focus exclusively on stellar evolution which is well understood and assume that planets remain in their orbits indefinitely. Many researchers believe that planets migrate due to gravitational interactions with each other and with smaller debris, but that is not shown in our simulator. We will make use of the Time and Simulation Controls panel. This panel consists of a button and slider to control the passing of time and 3 horizontal strips: • the first strip is a timeline encompassinging the complete lifetime of the star with time values labeled • the second strip represents the temperature range of the CHZ – the orange bar at the top indicates the inner boundary and the blue bar at the botom the outer Planet Mass e > 1.9 M Earth b > 15.6 M Earth c > 5.4 M Earth d > 7.1 M Earth

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