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Observing Exoplanets:Recording, reducing, and analyzing ground-based data
PTYS 195A
Rob ZellemRob ZellemPhD CandidatePhD Candidate
Lunar & Planetary Lunar & Planetary LaboratoryLaboratoryUniversity of ArizonaUniversity of Arizona
About me!• I am a giant nerd
– I love Star Wars!• I am a Planetary Astronomer
– I am trying to find alien life• Grew up in Nashville, TN
– Went to grade school and high school there• Went to college at Villanova University
– Degree in Astronomy and Astrophysics• MSc in Space Science at University College London• PhD candidate at LPL
– Structure and composition of exoplanets– Graduating at the latest this May
Course Website
• www.lpl.arizona.edu/~rzellem/PTYS_195A.html
• Will post lectures and assigned reading• Grades will be on D2L
– Assuming I can figure it out….
Course Objectives• Exoplanetary research indicates the existence of planets, a majority of
which are completely unlike those in our Solar System. Of the more than 1055 transiting exoplanets discovered to date, over 105 are giant planets, known as “hot Jupiters”, that have near-Jupiter masses and orbit close to their host stars. Due to their large planet-to-star contrast and being hosted by bright stars, these exoplanets are accessible with the University of Arizona’s 61” Kuiper telescope.
• Here students will record their own data on the 61”. We will learn how to reduce and analyze data from this platform.
• This class will culminate in a small group presentation on a specific exoplanet, potentially for inclusion in a published paper and Fall 2016 AAS poster presentation.
• Students will also develop presentation, critical thinking, and critiquing skills.
Class Format• The course will be conducted as a seminar, with a particular focus at each
meeting. Students are expected to have read the assigned material in advance and be ready to participate in the discussion.
• Two students will be assigned to lead each discussion with a short presentation on the required reading at the beginning of each class. Weekly reading will typically consist of about one published, peer-reviewed paper.
• Throughout the semester we will reduce a common dataset.• In the middle of the semester, we break down into smaller groups, which
each group assigned a specific target. This group will reduce this target and present their results and previously-published data in an 8 minute presentation at the end of the semester.
Textbook
• NONE! YAY!• Published papers available when you are on
UofA’s network
Grades
• 10% for being at the telescope for one observing run
• 10% weekly presentation• 10% weekly quizzes• 30% class-wide data reduction project• 40% final project (data reduction results 50%)
and PowerPoint presentation (50%)
Telescope Signup Sheet
Weekly Presentations• 2 students will give a short (8 minute) presentation on the weekly
assigned reading and help facilitate a discussion about the methods and results. Students will be graded with the following rubric with a 0 for not meeting the requirement and 2 for meeting the requirement:
• Read the paper• Addressed major paper concepts• Explained major concepts clearly and concisely• Facilitated discussion with peers and/or answered questions adequately• Ask questions in other students’ presentations (when not presenting)• BONUS (+1): Found a critique about the paper, only available to
presenting students
Weekly Quizzes
• At the beginning of each class, there will be a short quiz with questions on the previous class or the reading due for the present class. The aim for the daily quiz is to reinforce major class concepts and to provide the instructor with a proxy attendance grade. The lowest 2 quiz grades will be treated as extra credit.
POP QUIZ TIME!!!
Extra Credit
• The lowest 2 quiz grades will be treated as extra credit, to be added to the “Quiz” portion of the final grade calculation. In addition, there will be opportunities to go to public talks throughout the semester. Each student will be expected to take notes on the topic and get the signature of the instructor or the speaker for credit. Each opportunity will be treated as 1 additional point applied to their final numerical grade.
Academic Integrity
• It is strongly recommended that all students read the University of Arizona’s Code of Academic Integrity. All students in this course are expected to abide by this code.
• We will operate with the “3 strike method” for academic integrity issues: 1st offense will result in a 0 on the assignment in question, 2nd offense will result in a loss in a letter grade for the class (e.g., a student’s grade will be reduced from an “A” to a “B”), and 3rd offense will result in a course failure. ALL offenses will be reported to the University according to their Academic Integrity policy.
Planetary Transit Technique
Measures dimming of star light as planet passes in front
of (or behind) the star
Star-light dims less than 1%
Like looking for a firefly next to a lighthouse
Gives us the size (radius)
Planetary Transit Technique
Disadvantages: a) Bias towards large planets and in short period orbits b) False detections due to stellar variability c) Planet’s orbit must be seen edge-on from the observer point of view (so the planet passes in front of the star)
Advantages: a) Relatively cheap b) Can determine the size of the planet
Kepler Mission• Launched in 2009• Mission objective:
to discover Earth-like planets orbiting other stars
• As of February 2014, 961 confirmed planets– 2903 unconfirmed
planet candidates
NASA
Exoplanet Atmospheres• Transits allow the study of exoplanet
atmospheres– Can study how light varies at different
wavelengths – tells us about atmospheric structure and composition
Rob’s Thesis
• Observe transits of HD 209458b– One of the two brightest exoplanets– Hot Jupiter
• M = 0.714 Mjupiter
• R = 1.38 RJupiter
• 0.04747 AU away from its host star– 25 times closer to its star than the Earth is to the Sun– 9.5 times closer to its star than Mercury is to the Sun
• 3.52474859 day orbital period
– ~150 light-years away
UofA’s 61” Kuiper Telescope
Exoplanet Atmospheres
• Transits allow the study of gas giant atmospheres Griffith et al. 2014
Transit
• What is it measuring?
Transit
• The atmosphere + the planet’s disk
Transit
• The atmosphere + the planet’s optically-thick disk
Transit
• The atmosphere + the planet’s optically-thick disk
Transit
• Amount of atmospheric absorption will change with wavelength
Transit
• Amount of atmospheric absorption will change with wavelength
Beer’s Law
Transit
• So a planet’s radius will change with wavelength due to absorption by different molecules in its atmosphere
So….
• If we measure the transit of an exoplanet at different wavelengths…– We can measure how its radius varies with
wavelength– Indicates its atmospheric structure and content
• Atmospheric structure = how temperature varies with altitude
• Atmospheric content = what molecules are present
Example!
• Detection of H2 scattering
Zellem et al. (in prep.)
Example!
• Detection of H2 scattering
Another Example!
• Detection of water, methane, and carbon dioxide in a hot Jupiter’s atmosphere
Swain et al. (2009)
Measuring radii at the 61”
• Planet has same signature in the infrared (IR) despite differing atmospheric contents
• Signal very different in the opticaloptical
Benneke & Seager (2013)
Why are the IR signatures the same?
• In the IR, a small planet with a thick atmosphere can block as much light as a large planet with a small atmosphere– Hot Jupiter atmospheres are opaque in the IR
Why are the IR signatures the same?
• In the IR, a small planet with a thick atmosphere can block as much light as a large planet with a small atmosphere– Hot Jupiter atmospheres are opaque in the IR
=
However, not the same in the visible
• In the visible, the planet’s atmosphere is now transparent, so a small planet will look different than a large one
However, not the same in the visible
• In the visible, the planet’s atmosphere is now transparent, so a small planet will look different than a large one
≠
Rob does a spectroscopy trick
• IT’S AN ILLUSION, MICHAEL.
Measuring radii at the 61”
• Planet has same signature in the infrared (IR) despite differing atmospheric contents
• Signal very different in the opticaloptical
Benneke & Seager (2013)
Looking for New Planets
Looking for New Planets
Looking for New Planets
Looking for New Planets
Looking for New Planets
Looking for New Planets
Looking for New Planets
Looking for New Planets
Looking for New Planets
Looking for New Planets
Transit Timing Variations(TTVs)
Looking for Exomoons
Looking for Exomoons
Measuring Exoplanetary Magnetic Fields
Measuring Exoplanetary Magnetic Fields
In the UV In the B
Hubble Magnetic Field Detection
Fossati et al. (2010)
