Recommended
More Related Content
Similar to Slides_Detecting_Exoplanets_with_Transit_v2.pptx
Similar to Slides_Detecting_Exoplanets_with_Transit_v2.pptx (20)
Recently uploaded
Recently uploaded (20)
Slides_Detecting_Exoplanets_with_Transit_v2.pptx
- 1. Detecting Exoplanets by the Transit Method © Center for Astronomy Education University of Arizona 2014
- 2. The Kepler Orrery From the Caltech IPAC Exoplanet Archive: https://www.youtube.com/watch?v=gnZVvYm6KKM
- 3. The Kepler Telescope Image by NASA: http://www.nasa.gov/mission_pages/kepler/multimedia/images/kepler- spacecraft-cross-section.html
- 4. The Transit Method • When a star is orbited by an exoplanet, and the exoplanet moves between us and the star, some of the star’s light will be blocked, resulting in a decrease in the observed brightness of the star. • Telescopes (such as the Kepler telescope) can measure this decrease in observed brightness.
- 5. How It Looks • If you could zoom way in and look at a star being transited by a planet:
- 6. Step By Step • Think about how the light from the star is affected at each point.
- 7. The Important Graph • Astronomers observe the brightness of a star over a period of time and make a graph of the observed brightness vs. time. • Changes in the brightness of the star on this graph indicate the presence of an exoplanet orbiting the star.
- 8. How many of the below graphs correctly show how a star’s observed brightness will change over time if it is orbited by an exoplanet? A. Only one B. Two C. Three D. All four Brightness Time Brightness Time Brightness Time Brightness Time
- 10. Real Light Curves Data from the Faulkes Telescope Project: http://www.faulkes-telescope.com/news/2496
- 11. Planet Features • There are two important properties of the planet that we can find by this method: • The size of the exoplanet • The time it takes the exoplanet to complete an orbit around its parent star
- 12. Dip Features • Dip Depth – how much light is blocked – Deeper dip = larger planet • Dip Width – how long the transit takes – Wider dip = longer orbital period • Dip Sides – these are sloped! • Dip Bottom – this is flat.
- 13. Orbit Times • The time from the beginning of one dip to the beginning of the next dip is the time it takes the planet to complete one orbit. • The time between dips is longer than the duration of the dips themselves.
- 14. Kepler’s Third Law • If two planets are orbiting the same star, the planet that is further away moves slower. • The planet that is further away takes longer to complete an orbit.
- 15. Repeating Dips • If there is a single pattern of repeating dips that are all the same size and shape, with the same time between dips, then these dips are most likely caused by a single exoplanet. Brightness Time
- 16. The graph below shows how the observed brightness of a star changes over time because it is orbited by an exoplanet. Which location (A-D) in the exoplanet’s orbit corresponds to the time indicated by “X” on the graph? 3 12 Brightness Time (months) 6 18 15 9 x A planet’s orbit star to Earth B D C
- 17. A graph of brightness vs. time for a star orbited by an extrasolar planet is given below. Which property of the dips is NOT affected by the time it takes the planet to complete an orbit around its star? A. The spacing between dips B. The depth of the dips C. The slopes of the sides of the dips D. The widths of the bottoms of the dips Brightness Time
- 18. • When a star is orbited by multiple exoplanets, you can determine how many exoplanets there are from the pattern of dips in the graph of the star’s observed brightness vs. time. • This pattern of dips also allows you to determine the orbital periods and relative sizes of the planets from the graph. • Each exoplanet causes a unique repeating series of dips in the graph. Brightness Time Multiple Exoplanets
- 19. Multiple Exoplanets – No Overlap
- 20. Multiple Exoplanets – Overlapping
- 21. Overlapping, Step-by-Step • When two exoplanets transit their star at the same time, how will their overlapping dips appear on the graph of the star’s observed brightness vs. time?
- 22. 0 5 10 15 20 25 30 35 Brightness Time 0 5 10 15 20 25 30 35 Brightness Time Multiple Exoplanets – Overlapping dips
- 23. Lecture Tutorial – Detecting Exoplanets with the Transit Method (handout) • Work with a partner! • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. • Come to a consensus answer you both agree on. • If you get stuck or are not sure of your answer, ask another group. • If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask one of us for help.
- 24. Debrief • Let’s address any questions you have about the Lecture-Tutorial.
- 25. The graph below shows how the brightness of a star changes over time due to the fact that it is orbited by an extrasolar planet. How does the planet’s orbital period around its star compare to the orbital period of the Earth around the Sun? A. It is greater B. It is less C. They are equal D. Not enough information 3 12 Brightness Time (months) 6 18 15 9
- 26. You observe two identical stars (Star A and Star B), that are the same distance from Earth. Each graph below shows how the observed brightness of Star A or Star B changes over time. Which star is orbited by the larger exoplanet? A. Star A is orbited by a larger exoplanet. B. Star B is orbited by a larger exoplanet. C. Both extrasolar planets are the same size. D. There is not enough information to tell. 3 12 Brightness Time (months) 6 18 15 9 3 12 Brightness Time (months) 6 18 15 9 Star A Star B
- 27. You observe two identical stars (Star A and Star B), that are the same distance from Earth. Each graph below shows how the observed brightness of Star A or Star B changes over time. Which star has the exoplanet that orbits at a larger distance from its parent star? A. Star A’s exoplanet orbits at a larger distance. B. Star B’s exoplanet orbits at a larger distance. C. Both exoplanets orbit at the same distance. D. There is not enough information to tell. 3 12 Brightness Time (months) 6 18 15 9 3 12 Brightness Time (months) 6 18 15 9 Star A Star B
- 28. Star A has a small planet orbiting at a larger distance, and Star B has a large planet orbiting at a smaller distance. How should the graphs change to be correct? A. The time between dips in Graph A should be less than in Graph B. B. The sides of the dips in Graph A should be vertical. C. The dips in Graph A should be wider than in Graph B. D. The dips in Graph A should be deeper than in Graph B. 3 12 Brightness Time (months) 6 18 15 9 3 12 Brightness Time (months) 6 18 15 9 Star A Star B
- 29. The observed brightness vs. time for a star is represented by the graph below. Which of the following statements is true? A. The star is orbited by two planets with different sizes and different orbital periods. B. The star is orbited by two planets with the same size but different orbital periods. C. The star is orbited by two planets with different sizes and the same orbital period. D. The star is orbited by three planets with different sizes and different orbital periods. Brightness Time
- 30. If the graph below represents the brightness of our Sun as seen by an alien astronomer, which pair of bodies in our Solar System could produce the observed pattern of dips? A. Jupiter and Neptune B. Earth and Mars C. Neptune and Pluto D. Mars and Jupiter Brightness Time
- 31. Kepler Is Still Hunting Image by NASA: http://www.nasa.gov/content/sizes-of-known-exoplanets/ #.U9__3fldUnA
- 32. Thank You NASA! • The development of these materials was funded through the generous contributions of NASA's Exoplanet Exploration Program.
Editor's Notes
- The development of these materials was funded through the generous contributions of NASA's Exoplanet Exploration Program.
- This is a visualization of the various planetary system candidates found by the Kepler mission as of late 2013. There are 4,229 Kepler mission planet candidates as of June 25, 2014! See http://exoplanetarchive.ipac.caltech.edu/ for more info.
- This is the telescope that has found so many exoplanet candidates! http://www.nasa.gov/mission_pages/kepler/multimedia/images/kepler-spacecraft-cross-section.html
- The motion pauses at certain points so students can consider how much light is being blocked by the planet at those points.
- The correct answer is A. (the bottom right graph is correct) The top left and bottom left graphs are distractors that some students may believe to be correct choices.
- There is a graph of brightness vs. time with a transit “dip” hidden on the bottom half. It is revealed as the planet animates to the right. Students can observe how different points on the dip correspond to different parts of the planet’s transit.
- This is a graph of real data collected by high school students! - http://www.faulkes-telescope.com/news/2496 This slide is a good opportunity to plug citizen science efforts such as www.planethunters.org.
- It is beyond the scope of this Lecture-Tutorial to address some features of real light curves from transiting exoplanets. Due to competing variables, students are not asked to reason about the sides of the dips in transit light curves beyond that they are not vertical. Additionally, we do not require students to account for real-world transit dips not being flat. Instructors wishing to have their students reason about these concepts may choose to have their students complete this Lecture-Tutorial and then extend the lesson in their classes by introducing these features.
- This is a brief statement for students who have not seen Kepler’s laws before. Feel free to omit this slide if you have previously taught Kepler’s laws.
- The correct answer is C. This slide and the next will help assess your students’ understanding of the content before the Lecture-Tutorial.
- The correct answer is B.
- In this animation there is not a time when the two planets transit simultaneously. This is comparable to the case graphed on the previous slide.
- It can be helpful to have your students predict how the observed brightness of the star will change at different steps in the transit.
- Each of the blue vertical lines marks a particular “first”: The first time when we observe the full brightness of the star The first time when both planets are blocking light simultaneously The first time when more light is blocked than could be blocked by the large planet alone The first time when the maximum possible amount of light is blocked The first time when one planet has completed a transit while the other planet is still transiting
- The correct answer is C.
- The correct answer is B.
- The correct answer is A.
- The correct answer is C.
- The correct answer is A.
- The correct answer is D. The graph is not to scale! The expected reasoning for this question is to realize that there is a smaller planet with a shorter orbital period and a larger planet with a longer orbital period.
- Notice how much better we are getting at finding Earth-sized planets! http://www.nasa.gov/content/sizes-of-known-exoplanets/#.U9__3fldUnA