Copy of Lab 9 - Detecting Exoplanets.pdf

///- AST2002L Astronomy Lab Report Lab #9 Detecting Exoplanets List the names of all participating team members next to their role for this lab. ____________Isabella Adeeb___________________ ___________Aman Abera____________________ ___________Scott Beeks____________________ Big Idea: Astronomers now know of nearly 5,000 confirmed exoplanets, with thousands more potential candidates. The first exoplanet was discovered in 1992. Today, three-quarters of known exoplanets have been discovered using the transit method: when a planet passes directly between its star and an observer, it dims the star's light by a measurable amount. Lab Equipment: ● Exoplanet Transit Simulator: https://ccnmtl.github.io/astro-simulations/exoplanet-transit-simulator/

Part 1: Exploration In our Solar System, the orbits of the planets around the Sun are aligned nearly in the same plane (the Ecliptic). Because of this, there are times when we observers on Earth see Venus or Mercury pass across the face of the Sun. We call this a transit. If you were an astronaut outside our Solar System and you were aligned with the Ecliptic you would periodically see Jupiter and the other planets pass in front of the Sun. If you were so far away that you couldn’t resolve the Sun as a disk and only saw the Sun as a point of light, you would still see the light from the Sun dim temporarily as the planet passed in front of it and blocked out some of the Sun’s light. NASA missions like TESS and Kepler are designed to detect the transits of exoplanets as they pass in front of their sun. Because special alignment of the telescope with the disk of the other solar system is required to see a transit, which is not likely, these NASA missions observe very many stars. Even though such alignment is rare, there are so many stars with planets in our Galaxy that many transits have been observed. 1. If a star does not have a transiting planet, what will its light curve (a plot of stellar intensity versus time) look like? Sketch its light curve below. Use a brightness value of 1 as the average relative brightness of the star over a long period of time. 2. On the diagram below, sketch the observed relative brightness of the star corresponding to each position of the planet as shown.

Now open the Exoplanet Transit Simulator: https://ccnmtl.github.io/astro-simulations/exoplanet-transit-simulator/ This simulator shows what happens when an extrasolar planet transits in front of its star. The upper left panel shows the star and planet as they would be seen from earth if we had an extremely powerful telescope. The lightcurve is shown in the upper right panel. The apparent brightness of the star is 'normalized', that is, the brightness is reported as a fraction of the full brightness (when the star is not eclipsed). The planet, star, and system properties can be set in the lower panels. These parameters can also be set by selecting one of the presets from the dropdown menu in the Presets panel. Under Presets choose “1. Option A” and click the “Set” button. This option configures the simulator for Jupiter in a circular orbit of 1 AU with an inclination of 90°. 3. Determine how increasing each of the following variables would affect the depth and duration of the eclipse. Note that the transit duration is shown underneath the flux plot. Increasing the… Affects the eclipse duration Affects the eclipse depth Planet radius (increased from 1 to 2) 14.3hrs/365 day orbit became 15.6 hrs/365 day orbit 0.0106 became 0.0423 Planet semimajor axis (increased from 1 to 2) Increased to 20.2hrs/2.83 year orbit Depth stayed the same Eccentricity of orbit (increased from 0 to 0.4) Decreased the time to 13.1hrs/365 day orbit Depth stayed the same Stellar Mass (and thus temperature and radius) (increased from 1 to 2) Decreased to 16.3hrs/258 day orbit Depth decreased to 0.00375 Inclination of System (increased from 90 to 91) There is no eclipse There is no eclipse

4. What does the depth of the dip in the star’s light curve tell us about the planet and/or star? The depth lets you know the size of the planet in relation to the star. The deeper the depth the larger the planet. 5. You could also measure the width of the dip in the light curve. What does the width of the dip represent? The width represents the length of the eclipse. This correlates to the radius of the planet and mass of the star. 6. Will a planet further away from its star be moving faster or slower than a planet closer to its star? Explain why. A planet will move quicker when it is close to a star because of the gravitational pull of the star into its orbit. 7. How would the width of the dip change if the planet was close or farther away from the star? If the planet is closer then the width would decrease because the planet will move faster causing the eclipse time to decrease. 8. What property or properties of the star do we need to know in order to calculate the actual size of the planet?” Explain. (Hint: you might consider the H-R Diagram, Kepler’s or Newton’s Laws of gravity.) You need to know depth of the light curve dip to determine the size of planet, as well as, the radius of the star.

Part 2: Does the Evidence Match a Given Conclusion? In the Exoplanet Transit Simulator, you have the option of showing simulated noisy measurements and hiding the theoretical curve — this gives a better idea of what it is like working with real data. NASA’s Kepler mission photometrically detected 2,662 extrasolar planets during transit. It had a typical photometric accuracy of 1 part in 50,000 (a noise of 0.00002) and sampled a star’s brightness about once every minute. 9. Select “2. Option B” and click “Set.” This preset is very similar to the Earth in its orbit (Note that Jupiter is more than 300 times the mass of Earth). Select show simulated measurements and set the noise to 0.00002. Do you think Kepler will be able to detect Earth-sized planets in transit? Explain your reasoning and cite specific evidence from your simulations to justify your answer. Yes I think Kepler will be able to detect Earth-sized planets in transit, but given enough time. It would take many years to note multiple rotations as an orbit is 365 days. 10. How long does the eclipse of an earth-like planet take? How much time passes between eclipses? Use the simulator to answer these questions. Based on your findings, how long would the Kepler mission need to operate in order to detect an earth-like planet? Eclipse takes 13.1 hours of a 365 day orbit. Three transits are necessary to be confident in exoplanet findings, so at least three or more years to detect an earth-like planet. The Exoplanet Transit Simulator has several presets which contain the measured properties of real exoplanet systems. These nine presets represent some of the first exoplanets detected using the transit method. 11. One-by-one, select the presets and click “Set” to display the exoplanet properties. Make a table of the important exoplanet properties and attach it below. What properties do

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