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ASTR 28900

Adina
November 09, 2022

ASTR 28900

Exoplanet detection and confirmation techniques for UChicago Undergraduate Research Seminar (Spring 2022)

Adina

November 09, 2022
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  1. ADINA FEINSTEIN — MAY 16, 2022 ASTR 28900 THE “HOW

    TO” ON FINDING & CONFIRMING EXOPLANETS 1
  2. THINGS YOU’LL LEARN BY THE END OF THIS TALK (HOPEFULLY)

    - What is an exoplanet? - What do transits and radial velocities tell us about exoplanets? - How does someone confirm an exoplanet? - What does the population of exoplanets look like? - What can young planets tell us that old planets can’t? 2
  3. WHAT IS AN EXOPLANET? 3

  4. WHAT IS AN EXOPLANET? 4

  5. WHAT IS AN EXOPLANET? 4

  6. -Is in orbit around the Sun -Has su ffi cient

    enough mass to become spherical (or nearly spherical) in shape -Has cleared its orbital path from other Solar System “stu ff ” WHAT IS AN EXOPLANET? 4
  7. -Is in orbit around the Sun -Has su ffi cient

    enough mass to become spherical (or nearly spherical) in shape -Has cleared its orbital path from other Solar System “stu ff ” WHAT IS AN EXOPLANET? 5 -“Exo” is short for “extrasolar” or… outside of the Sun
  8. THE FIRST EXOPLANETS 6

  9. THE FIRST EXOPLANETS 6

  10. THE TRANSIT METHOD 7

  11. THE CONCEPT 8 TOP DOWN VIEW EDGE ON VIEW

  12. THE CONCEPT 8 TOP DOWN VIEW EDGE ON VIEW

  13. THE CONCEPT 8 TOP DOWN VIEW EDGE ON VIEW

  14. PHOTOMETRY — MONITORING THE BROADBAND LIGHT FROM STARS 9

  15. PHOTOMETRY — MONITORING THE BROADBAND LIGHT FROM STARS 9 Ɣ

    Ɣ Ɣ Ɣ Ɣ
  16. PHOTOMETRY — MONITORING THE BROADBAND LIGHT FROM STARS 9 e

    e e e e
  17. PHOTOMETRY — MONITORING THE BROADBAND LIGHT FROM STARS 9 e

    e e e e
  18. BREAKING DOWN THE INFO IN A TRANSIT 10

  19. MOST IMPORTANTLY: TRANSIT DEPTH 11 TRANSIT DEPTH Observable: planet-to-star fl

    ux ratio Inferred parameter: planet radius
  20. 12 TRANSIT DEPTH RSTAR RPLANET d = ( Rstar Rplanet

    ) 2 MOST IMPORTANTLY: TRANSIT DEPTH
  21. SECOND: TRANSIT PERIOD 13 PLANET PERIOD TOP DOWN VIEW

  22. THIRD: TRANSIT DURATION 14 TRANSIT DURATION t = P 2Rstar

    2πa
  23. THIRD: TRANSIT DURATION 14 TRANSIT DURATION t = P 2Rstar

    2πa
  24. THIRD: TRANSIT DURATION 15 TRANSIT DURATION t = P 2Rstar

    2πa P2 = 4π2 G(Mstar + Mplanet ) a3 KEPLER’S THIRD LAW
  25. THIRD: TRANSIT DURATION 15 TRANSIT DURATION t = P 2Rstar

    2πa P2 = 4π2 G(Mstar + Mplanet ) a3 KEPLER’S THIRD LAW
  26. ADDITIONAL ORBITAL PROPERTIES LEARNED 16 i INCLINATION how inclined the

    orbit is with respect to the stellar equator
  27. ADDITIONAL ORBITAL PROPERTIES LEARNED 17 INCLINATION how inclined the orbit

    is with respect to the stellar equator IMPACT PARAMETER: what latitude the planet transits i a b b bR* = a cos i RSTAR
  28. ADDITIONAL ORBITAL PROPERTIES LEARNED 18 INCLINATION how inclined the orbit

    is with respect to the stellar equator IMPACT PARAMETER: what latitude the planet transits b
  29. ADDITIONAL ORBITAL PROPERTIES LEARNED 18 INCLINATION how inclined the orbit

    is with respect to the stellar equator IMPACT PARAMETER: what latitude the planet transits b
  30. ADDITIONAL ORBITAL PROPERTIES LEARNED 18 INCLINATION how inclined the orbit

    is with respect to the stellar equator IMPACT PARAMETER: what latitude the planet transits b
  31. LIMB DARKENING 19 - At the edges of the star,

    we see the cooler, darker, outer layers of the atmosphere - At the center, we see the hotter brighter inner layers - At an intermediate distance, we see warm layers (hence the gradient)
  32. ADDITIONAL ORBITAL PROPERTIES LEARNED 20 INCLINATION ECCENTRICITY how circular the

    orbit is how inclined the orbit is with respect to the stellar equator IMPACT PARAMETER what latitude the planet transits TOP DOWN VIEW
  33. ADDITIONAL ORBITAL PROPERTIES LEARNED 21 INCLINATION ECCENTRICITY how circular the

    orbit is how inclined the orbit is with respect to the stellar equator IMPACT PARAMETER what latitude the planet transits TOP DOWN VIEW KEPLER’S FIRST LAW The orbits of planetary bodies are ellipses, with the star at one of the foci of the ellipse.
  34. INCLINATION ADDITIONAL ORBITAL PROPERTIES LEARNED 22 how circular the orbit

    is ECCENTRICITY how inclined the orbit is with respect to the stellar equator IMPACT PARAMETER what latitude the planet transits
  35. INCLINATION ADDITIONAL ORBITAL PROPERTIES LEARNED 22 how circular the orbit

    is ECCENTRICITY how inclined the orbit is with respect to the stellar equator IMPACT PARAMETER what latitude the planet transits
  36. INCLINATION ADDITIONAL ORBITAL PROPERTIES LEARNED 22 how circular the orbit

    is ECCENTRICITY how inclined the orbit is with respect to the stellar equator IMPACT PARAMETER what latitude the planet transits
  37. 23 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Radius [REarth] Transit

    Depth around the Sun [%] Earth 1 0.08 Neptune 4 0.1 Jupiter 10 1
  38. 23 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Radius [REarth] Transit

    Depth around the Sun [%] Earth 1 0.08 Neptune 4 0.1 Jupiter 10 1
  39. 23 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Radius [REarth] Transit

    Depth around the Sun [%] Earth 1 0.08 Neptune 4 0.1 Jupiter 10 1
  40. 23 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Radius [REarth] Transit

    Depth around the Sun [%] Earth 1 0.08 Neptune 4 0.1 Jupiter 10 1
  41. 23 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Radius [REarth] Transit

    Depth around the Sun [%] Earth 1 0.08 Neptune 4 0.1 Jupiter 10 1
  42. 23 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Radius [REarth] Transit

    Depth around the Sun [%] Earth 1 0.08 Neptune 4 0.1 Jupiter 10 1
  43. 23 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Radius [REarth] Transit

    Depth around the Sun [%] Earth 1 0.08 Neptune 4 0.1 Jupiter 10 1
  44. THE RADIAL VELOCITY METHOD 24

  45. THE CONCEPT 25

  46. THE CONCEPT 25

  47. THE CONCEPT 25

  48. SPECTROSCOPY — MONITORING STELLAR ABSORPTION LINES 26

  49. SPECTROSCOPY — MONITORING STELLAR ABSORPTION LINES 26

  50. BREAKING DOWN THE INFO IN RADIAL VELOCITIES 27

  51. BREAKING DOWN THE INFO IN RADIAL VELOCITIES 28 PERIOD Observable:

    the motion of the star Inferred parameter: planet period
  52. BREAKING DOWN THE INFO IN RADIAL VELOCITIES 29 AMPLITUDE K

    = 203P−1/3 Mp sin i (M⋆ + wMp )2/3 1 1 − e2
  53. BREAKING DOWN THE INFO IN RADIAL VELOCITIES 29 AMPLITUDE K

    = 203P−1/3 Mp sin i (M⋆ + wMp )2/3 1 1 − e2
  54. 30 K = 203P−1/3 Mp sin i (M⋆ + wMp

    )2/3 1 1 − e2 BREAKING DOWN THE INFO IN RADIAL VELOCITIES
  55. 30 K = 203P−1/3 Mp sin i (M⋆ + wMp

    )2/3 1 1 − e2 BREAKING DOWN THE INFO IN RADIAL VELOCITIES
  56. 31 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Mass [MEarth] Radial

    Velocity Signal [m/s] Earth 1 0.09 Neptune 16 1.5 Jupiter 320 28
  57. 31 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Mass [MEarth] Radial

    Velocity Signal [m/s] Earth 1 0.09 Neptune 16 1.5 Jupiter 320 28
  58. 31 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Mass [MEarth] Radial

    Velocity Signal [m/s] Earth 1 0.09 Neptune 16 1.5 Jupiter 320 28
  59. 31 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Mass [MEarth] Radial

    Velocity Signal [m/s] Earth 1 0.09 Neptune 16 1.5 Jupiter 320 28
  60. 31 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Mass [MEarth] Radial

    Velocity Signal [m/s] Earth 1 0.09 Neptune 16 1.5 Jupiter 320 28
  61. 31 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Mass [MEarth] Radial

    Velocity Signal [m/s] Earth 1 0.09 Neptune 16 1.5 Jupiter 320 28
  62. 31 GOOD REFERENCE NUMBERS TO REMEMBER Planetary Mass [MEarth] Radial

    Velocity Signal [m/s] Earth 1 0.09 Neptune 16 1.5 Jupiter 320 28
  63. WHAT CAN WE LEARN ABOUT EXOPLANETS IF WE HAVE BOTH

    THEIR RADII AND MASSES? 32 ρ = M 4 3 πR3 THE PLANET’S DENSITY!
  64. MASS - RADIUS DIAGRAM 33 (Zeng et al 2019)

  65. CONFIRMING A TRANSITING PLANET IS REAL 34

  66. STEPS IN THE CONFIRMATION PROCESS (FOR TRANSITING PLANETS) 35 STEP

    1: FIND A TRANSIT SIGNAL (IDEALLY 3)
  67. STEPS IN THE CONFIRMATION PROCESS (FOR TRANSITING PLANETS) 35 STEP

    1: FIND A TRANSIT SIGNAL (IDEALLY 3) STEP 2: OBSERVE ANOTHER TRANSIT FROM THE GROUND
  68. STEPS IN THE CONFIRMATION PROCESS (FOR TRANSITING PLANETS) 35 STEP

    1: FIND A TRANSIT SIGNAL (IDEALLY 3) STEP 2: OBSERVE ANOTHER TRANSIT FROM THE GROUND STEP 3: CHARACTERIZE THE HOST STAR
  69. STEPS IN THE CONFIRMATION PROCESS (FOR TRANSITING PLANETS) 35 STEP

    1: FIND A TRANSIT SIGNAL (IDEALLY 3) STEP 2: OBSERVE ANOTHER TRANSIT FROM THE GROUND STEP 3: CHARACTERIZE THE HOST STAR STELLAR PROPERTIES SEARCH FOR BINARY COMPANIONS
  70. STEPS IN THE CONFIRMATION PROCESS (FOR TRANSITING PLANETS) 35 STEP

    1: FIND A TRANSIT SIGNAL (IDEALLY 3) STEP 2: OBSERVE ANOTHER TRANSIT FROM THE GROUND STEP 3: CHARACTERIZE THE HOST STAR STEP 4: THEORIZE SOME STUFF ABOUT THE PLANET STELLAR PROPERTIES SEARCH FOR BINARY COMPANIONS
  71. STEP 1: IDENTIFYING TRANSITS IN A LIGHT CURVE 36 KEPLER/K2

    TRANSITING EXOPLANET SURVEY SATELLITE (TESS)
  72. - Want to make sure the transit signal / period

    are real and not instrumental systematics STEP 2: GROUND-BASED TRANSIT 37 Next Generation Transit Survey (NGTS) Mearth
  73. - From transit — planet-to-star radius ratio - From radial

    velocities — planet-to-star mass ratio STEP 3A: STELLAR PROPERTIES 38
  74. - This uses a technique called “adaptive optics imaging” which

    searches for binary star companions, which may also cause transit events (these are called eclipsing binaries). STEP 3B: IDENTIFYING BINARY COMPANIONS 39
  75. - This uses a technique called “adaptive optics imaging” which

    searches for binary star companions, which may also cause transit events (these are called eclipsing binaries). STEP 3B: IDENTIFYING BINARY COMPANIONS 39
  76. - This uses a technique called “adaptive optics imaging” which

    searches for binary star companions, which may also cause transit events (these are called eclipsing binaries). STEP 3B: IDENTIFYING BINARY COMPANIONS 39
  77. - Dynamical arguments: looking into the longterm stability of the

    system - For multi-planet systems: looking for transit timing variations as another means to measure the planetary masses - Modeling transmission spectra: what absorption features you would see from the planetary atmospheres - Only for transiting exoplanets - Dependent on planet radius, mass, orbital period/equilibrium temperature STEP 4: DISCUSS & PROPOSE 40
  78. WHAT DOES THE CURRENT POPULATION OF EXOPLANETS LOOK LIKE? 41

  79. ~4500 PLANETS HAVE MEASURED RADII 42 Jupiter Earth

  80. ~4500 PLANETS HAVE MEASURED RADII 42 Jupiter Earth

  81. ~4500 PLANETS HAVE MEASURED RADII 42 Jupiter Earth

  82. WHERE ARE ALL THE ~1.8REARTH PLANETS? 43 (Fulton et al

    2017)
  83. WHAT DO WE THINK CAUSES THIS GAP? 44

  84. WHAT DO WE THINK CAUSES THIS GAP? 44 Have gaseous

    
 envelopes No atmospheres
  85. GAP THEORY: PHOTOEVAPORATION 45 Have gaseous 
 envelopes No atmospheres

  86. GAP THEORY: PHOTOEVAPORATION 45 Have gaseous 
 envelopes No atmospheres

  87. < 1000 PLANETS HAVE MEASURED MASSES 46 Jupiter Earth

  88. YOUNG PLANETS & WHAT THEY TEACH US 47

  89. THERE ARE <100 TRANSITING PLANETS YOUNGER THAN 300 MYR 48

    Jupiter Earth
  90. TRANSITS — TOO EASY TO BE TRUE 49 Implies a

    well- behaved star
  91. WELL-BEHAVED = STELLAR SURFACE IS BORING 50

  92. WELL-BEHAVED = STELLAR SURFACE IS BORING 50

  93. THIS IS NOT A RADIAL VELOCITY CURVE! 51

  94. THIS IS NOT A RADIAL VELOCITY CURVE! 52

  95. THIS IS NOT A RADIAL VELOCITY CURVE! 52

  96. 53 YOUR TURN TO FIND THE PLANET

  97. 53 YOUR TURN TO FIND THE PLANET

  98. V1298 TAU — 4 PLANETS AROUND A 30 MYR STAR

    54 (David et al 2019)
  99. V1298 TAU — 4 PLANETS AROUND A 30 MYR STAR

    54 (David et al 2019)
  100. V1298 TAU — STELLAR CHARACTERIZATION 55 (David et al 2019)

    - Placing membership with a nearby young moving group - Kinematics argument - HR diagram argument - Rotation period
  101. V1298 TAU — STELLAR CHARACTERIZATION 55 (David et al 2019)

    - Placing membership with a nearby young moving group - Kinematics argument - HR diagram argument - Rotation period
  102. V1298 TAU — STELLAR CHARACTERIZATION 55 (David et al 2019)

    - Placing membership with a nearby young moving group - Kinematics argument - HR diagram argument - Rotation period
  103. V1298 TAU — STELLAR CHARACTERIZATION 55 (David et al 2019)

    - Placing membership with a nearby young moving group - Kinematics argument - HR diagram argument - Rotation period
  104. V1298 TAU — “WATCHING” RADIUS EVOLUTION 56 (David et al

    2019)
  105. V1298 TAU — AN EXAMPLE OF HOW CHALLENGING YOUNG PLANETS

    ARE 57 (Suarez Mascareño et al 2021)
  106. V1298 TAU — AN EXAMPLE OF HOW CHALLENGING YOUNG PLANETS

    ARE 57 (Suarez Mascareño et al 2021) No known 
 orbital period 
 from transits 
 (claim ~40 days from RVs) Well constrained 
 orbital period 
 of ~24 days
  107. V1298 TAU — WHAT’S UP WITH THEIR DENSITIES? 58 Density

    (g/cm3) Jupiter 1.33 Saturn 0.69 V1298 Tau b 1.2 ± 0.45 V1298 Tau e 3.6 ± 1.6
  108. V1298 TAU — THE WRONG PERIOD FOR PLANET E 59

    (Feinstein et al 2022) 😬 New TESS data gave 
 lower period of V1298 Tau e 
 of >= 42.7 days
  109. V1298 TAU — SO WHAT HAPPENED? 60 - Young stars

    are variable, active, and this manifests in their own intrinsic radial velocities - Speci fi cally, young stellar RVs are dominated by magnetic activity - Young stars have strong stellar winds - Eventually, they will lose angular momentum via winds & spin down (decreases magnetic activity) - This period could be intrinsic to the star, not the planet - Timescales of stellar activity RVs are dependent on the star
  110. THINGS YOU’VE LEARNED TODAY (HOPEFULLY) - What is an exoplanet?

    - What do transits tell us about exoplanets? - What do radial velocities tell us about exoplanets? - How does someone confirm an exoplanet? - What does the population of exoplanets look like? - What can young planets tell us that old planets can’t? 61 afeinstein@uchicago.edu
  111. THINGS YOU’VE LEARNED TODAY (HOPEFULLY) - What is an exoplanet?

    - What do transits tell us about exoplanets? - What do radial velocities tell us about exoplanets? - How does someone confirm an exoplanet? - What does the population of exoplanets look like? - What can young planets tell us that old planets can’t? 61 afeinstein@uchicago.edu
  112. THINGS YOU’VE LEARNED TODAY (HOPEFULLY) - What is an exoplanet?

    - What do transits tell us about exoplanets? - What do radial velocities tell us about exoplanets? - How does someone confirm an exoplanet? - What does the population of exoplanets look like? - What can young planets tell us that old planets can’t? 61 afeinstein@uchicago.edu
  113. THINGS YOU’VE LEARNED TODAY (HOPEFULLY) - What is an exoplanet?

    - What do transits tell us about exoplanets? - What do radial velocities tell us about exoplanets? - How does someone confirm an exoplanet? - What does the population of exoplanets look like? - What can young planets tell us that old planets can’t? 61 afeinstein@uchicago.edu
  114. THINGS YOU’VE LEARNED TODAY (HOPEFULLY) - What is an exoplanet?

    - What do transits tell us about exoplanets? - What do radial velocities tell us about exoplanets? - How does someone confirm an exoplanet? - What does the population of exoplanets look like? - What can young planets tell us that old planets can’t? 61 afeinstein@uchicago.edu
  115. THINGS YOU’VE LEARNED TODAY (HOPEFULLY) - What is an exoplanet?

    - What do transits tell us about exoplanets? - What do radial velocities tell us about exoplanets? - How does someone confirm an exoplanet? - What does the population of exoplanets look like? - What can young planets tell us that old planets can’t? 61 afeinstein@uchicago.edu