Name Habitable Zones – Student GuideExercisesPlease r.docx
- 1. Name: Habitable Zones – Student Guide Exercises 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
- 2. outside it appears “frozen”. 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. CHZ Inner Boundary CHZ Outer Boundary Width of CHZ NAAP – Habitable Zones 1/7 Question 2: 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
- 3. 1.0 2.0 4.0 8.0 15.0 Question 3: Using the table above, what general conclusion can be made regarding the location of the CHZ for different types of stars?
- 4. Question 4: 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: 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?
- 5. 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 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
- 6. 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 boundary. A black line is shown in between for times when the planet is within the CHZ. · The bottom strip also shows the length of time the planet is in the CHZ in dark blue as well as labeling important events during the lifetime of a star such as when it leaves the main sequence. Stars gradually brighten as they get older. They are building up a core of helium ash and the fusion region becomes slightly larger over time, generating more energy. Question 8: Return to the none selected mode and configure the simulator for Earth (a 1 M star at a distance of 1 AU). 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
- 7. 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? You may have noticed the planet moving outwards towards the end of the star’s life. This is due to the star losing mass in its final stages. We know that life appeared on Earth early on but complex life did not appear until several billlion years later. If life on other planets takes a similar amount of time to evolve, we would like to know how long a planet is in its CHZ to evaluate the likelihood of complex life being present. To make this determination, first set the timeline cursor to time zero, then drag the planet in the diagram so that it is just on the outer edge of CHZ. Then run the simulator until the planet is no
- 8. longer in the CHZ. Record the time when this occurs – this is the total amount of time the planet spends in the CHZ. Complete the table for the range of stellar masses. 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. Tidal Locking We have learned that large stars are not good candidates for life because they evolve so quickly. Now let’s take a look at low- mass stars. Reset the simulator and set the initial star mass to 0.3 M . Drag the planet in to the CHZ.
- 9. 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?
- 10. CHZ Summation We have seen that low-mass stars have very small CHZs very close to the star and that planets become tidally locked at these small distances. We have seen that high-mass stars have very short lives – too short for life as we know it to appear. The combination of these two trains of thought is often referred to as the Goldilocks hypothesis – that medium-mass stars give the optimal opportunity for complex life to appear. GHZ Now we are going to investigate habitability zones on the scale of the entire Milky Way Galaxy. The two competing factors that we will look at are 1) the likelihood of planets forming (since we assume that life needs a planet to evolve on), and 2) the likelihood of life being wiped out by a cosmic catastrophe. Open up the Milky Way Habitabilty Explorer. Each of the two factors described above are illustrated in a graph as a function of distance from the galactic center. 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?
- 11. 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.
- 12. Codes of ethical conduct at Ruby Tuesday Aaron Whitaker Professor: Michael Oswald Business 100 12/12/2016 MICHAEL OSWALD MICHAEL OSWALD: only double space between lines
- 13. Codes of ethical conduct at Ruby Tuesday Introduction Code of ethics is an set of rules that is used in guiding a given organization or company. All successful organizations usually have a set of rules that govern their employees within the organization. These rules are usually of great importance as they lead to uniformity among employees and even members of an organization's staff and management. Just as any other successful and competitive organization, Ruby Tuesday has set of rules that govern individuals within the organization. These codes of conduct are usually implemented in such a way that every individual within the organization benefits equally without any form of bias (Gilman, 2005). Codes of ethical conduct of Ruby Tuesday The organization has a code of ethical conduct that has to be followed by the employees and even the organization's staff. Some of the most important elements of the organization's code
- 14. of conduct include the following: • Any individual who is part of the organization should be capable of acting with honesty and integrity between members of the community. Also, this is mainly used in ensuring that the relationship between professionals and personal relationships are kept at par. This is quite important ensuring that any information that may give rise to conflicts within the organization reaches the company's Chief Legal Officer and this helps in ensuring that the number of conflicts within the organization are reduced (Gilman, 2005). MICHAEL OSWALD MICHAEL OSWALD: center and bold MICHAEL OSWALD MICHAEL OSWALD: a MICHAEL OSWALD MICHAEL OSWALD: centere and bold • Any individual within the organization is entitled to providing information that is accurate, timely, full and fair to all documents and reports that
- 15. the company should be delivering to SEC or other public filings or any sort of communication that has been made by the company. • Any individual within the company should be ready to comply with the laws and rules of the company, court orders and even the company's regulations. Also, these individuals should be ready to comply faithfully with the consent agreements of state, foreign, national and local governments and any form of regulatory agencies that will be applicable. • All individuals within the company should be able to act responsibly and in good faith. They should also be able to care for the company's customers by offering them with quality goods and services. • The company's employees and staff should not use any form of confidential information acquired during work experience within the company to one's own advantage. Also, these individuals should refrain from buying or even selling the
- 16. securities of the company as this will be termed as a violation of the company's security laws. • An individual should be able to act responsibly on any activity taking place within the company (Whitton, 2001). Key steps that Ruby Tuesday should apply In order to ensure that all the employees and the company's staff fully comply with the company's codes of ethical conduct, the company should follow the steps below: MICHAEL OSWALD MICHAEL OSWALD: need punctuation : • The company should first identify the strengths and weaknesses of its employees and staff • Next, they should ensure that all stakeholders in the company are aware of the codes of ethical conduct that have been administered by the company • The company should then involve all members of the company in decision making
- 17. processes in order to come up with the right set of rules and regulations that will help in governing the company. If these steps are followed then the individuals in the company will be able to fully follow the codes of ethical conduct (Whitton, 2001). Ways of being responsive • The restaurant can perform assessments in order to hear from its employees • The restaurant can involve both employees and the staff in decision making processes • The restaurant should also ensure that employees and staff are all involved while making any decisions regarding change in the codes of ethical conduct. MICHAEL OSWALD MICHAEL OSWALD: period MICHAEL OSWALD MICHAEL OSWALD: period
- 18. MICHAEL OSWALD MICHAEL OSWALD: need punctuation MICHAEL OSWALD MICHAEL OSWALD: period MICHAEL OSWALD MICHAEL OSWALD: period MICHAEL OSWALD MICHAEL OSWALD: this paper seems to end abruptly. There should be some sort of conclusion. References Gilman, S. C. (2005). Ethics codes and codes of conduct as tools for promoting an ethical and professional public service: comparative successes and lessons. Washington DC. Whitton, H. (2001). Implementing effective ethics standards in government and the civil service. Transparency International, 2, 2001. MICHAEL OSWALD MICHAEL OSWALD: center MICHAEL OSWALD MICHAEL OSWALD: why didn't you utilize Ruby Tuesday website as a resource?