Exoplanet Detection Techniques I GUASA 12/10/2013 Prof. Sara Seager MIT - PowerPoint PPT Presentation

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Exoplanet Detection Techniques I GUASA 12/10/2013 Prof. Sara Seager MIT

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  1. Exoplanet Detection Techniques I GUASA 12/10/2013 Prof. Sara Seager MIT

  2. Exoplanet Detection Techniques I • Introduction • Planet Definition • List of Planet Detection Techniques • Planet Detection Techniques in More Detail • Radial Velocity • Transits • Lecture I Summary

  3. Planet Occurrence from Kepler Fraction of stars with planets (P < 50 days) Planet size (relative to Earth) Howard, 2013

  4. Planet Occurrence from Ground-Based RV Fraction of stars with planets (P < 50 days) Planet mass (relative to Earth) Howard, 2013

  5. Known Planets 2013 Based on data compiled by J. Schneider

  6. http://eyes.jpl.nasa.gov/exoplanets/index.html

  7. Exoplanet Detection Techniques I • Introduction • Planet Definition • List of Planet Detection Techniques • Planet Detection Techniques in More Detail • Radial Velocity • Transits • Lecture I Summary

  8. What is a Planet? ?

  9. What is a Planet? Planet sizes are to scale. Separations are not. Characterizing extrasolar planets: very different from solar system planets, yet solar system planets are their local analogues

  10. What is a Planet? • No satisfactory definition. • There is an official definition, that was socially engineered

  11. What is a Planet? • The IAU members gathered at the 2006 General Assembly agreed that a "planet" is defined as a celestial body that • (a) is in orbit around the Sun, • (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and • (c) has cleared the neighbourhood around its orbit.

  12. Official definition precipitated by “new Plutos”, the so-called dwarf planets • For an interesting discussion see • http://www.gps.caltech.edu/~mbrown/eightplanets/ • http://www.gps.caltech.edu/~mbrown/dwarfplanets/ and links therein. Figure credit M. Brown

  13. What is an Exoplanet? • The IAU WGESP has agreed to the following statements (subject to change): • 1) Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars or stellar remnants are "planets" (no matter how they formed). The minimum mass/size required for an extrasolar object to be considered a planet should be the same as that used in our Solar System. • 2) Substellar objects with true masses above the limiting mass for thermonuclear fusion of deuterium are "brown dwarfs", no matter how they formed nor where they are located. • 3) Free-floating objects in young star clusters with masses below the limiting mass for thermonuclear fusion of deuterium are not "planets", but are "sub-brown dwarfs" (or whatever name is most appropriate).

  14. What is an Exoplanet? • A planet outside of our solar system

  15. Who Can Name Exoplanets? • In 2009, the Organizing Committee of IAU Commission 53 Extrasolar Planets (WGESP) on exoplanets discussed the possibility of giving popular names to exoplanets in addition to their existing catalogue designation (for instance HD 85512 b). Although no consensus was reached, the majority was not in favour of this possibility at the time. • However, considering the ever increasing interest of the general public in being involved in the discovery and understanding of the Universe, the IAU decided in 2013 to restart the discussion of the naming procedure for exoplanets and assess the need to have popular names as well. In 2013 the members of Commission 53 will be consulted in this respect and the result of this will be made public on this page. • The nomenclature for exoplanets is indeed a difficult matter that deserves careful attention in many aspects. Such a system must take into account that discoveries are often tentative, later to be confirmed or rejected, possibly by several different methods, and that several planets belonging to the same star may eventually be discovered, again possibly by different means. Thus, considerable care and experience are required in its design. • http://www.iau.org/public/themes/naming/#exoplanets • http://www.iau.org/static/public/naming/planets_and_satellites.pdf

  16. Exoplanet Detection Techniques I • Introduction • Planet Definition • List of Planet Detection Techniques • Planet Detection Techniques in More Detail • Radial Velocity • Transits • Lecture I Summary

  17. Wikipedia List • 1 Established detection methods • 1.1 Radial velocity • 1.2 Transit method • 1.3 Orbital light variations (direct non-resolved detection) • 1.4 Light variations due to Relativistic Beaming • 1.5 Light variations due to ellipsoidal variations • 1.6 Timing variations • 1.6.1 Pulsartiming • 1.6.2 Pulsation frequency (variable star timing) • 1.6.3 Transit timing variation method (TTV) • 1.6.4 Transit duration variation method (TDV) • 1.6.5 Eclipsing binary minima timing • 1.7 Gravitational microlensing • 1.8 Direct imaging • 1.8.1 Early discoveries • 1.8.2 Imaging instruments • 1.9 Polarimetry • 1.10 Astrometry Wow! Way too many concepts.

  18. Wikipedia List • 1 Established detection methods • 1.1 Radial velocity • 1.2 Transit method • 1.3 Orbital light variations (direct non-resolved detection) • 1.4 Light variations due to Relativistic Beaming • 1.5 Light variations due to ellipsoidal variations • 1.6 Timing variations • 1.6.1 Pulsartiming • 1.6.2 Pulsation frequency (variable star timing) • 1.6.3 Transit timing variation method (TTV) • 1.6.4 Transit duration variation method (TDV) • 1.6.5 Eclipsing binary minima timing • 1.7 Gravitational microlensing • 1.8 Direct imaging • 1.8.1 Early discoveries • 1.8.2 Imaging instruments • 1.9 Polarimetry • 1.10 Astrometry

  19. Known Planets 2013 Based on data compiled by J. Schneider

  20. The points show the masses versus semimajor axis in units of the snow line distance for the exoplanets that have been discovered by various methods as of Dec. 2011. See the Extrasolar Planets Encyclopedia (http://exoplanet.eu/) and the Exoplanet Data Explorer (http://exoplanets.org/). Here we have taken the snow line distance to be asl = 2.7 AU(M∗/M⊙). Radial velocity detections (here what is actually plotted is Mp sin i) are indicated by red circles (blue for those also known to be transiting), transit detections are indicated by blue triangles if detected from the ground and as purple diamonds if detected from space, microlensing detections are indicated by green pentagons, direct detections are indicated by magenta squares, and detections from pulsar timing are indicated by yellow stars. The letters indicate the locations of the Solar System planets. The shaded regions show rough estimates of the sensitivity of various surveys using various methods, demonstrating their complementarity. Wright and Gaudi 2012, arXiv:1210.2471

  21. Ideally we would learn how to write down all of these equations. But this would be a whole week of classes

  22. Exoplanet Detection Techniques I • Introduction • Planet Definition • List of Planet Detection Techniques • Planet Detection Techniques in More Detail • Radial Velocity • Transits • Lecture I Summary

  23. Radial Velocity Preview K Mayor and Queloz 1995 Today we will estimate exoplanet mass from radial velocity data sets

  24. RV Lecture Contents • Radial Velocity Definition • Planet Mass Derivation • Tour of Radial Velocity Curves • Measuring Planet Masses • Controversial RV Planet Detections

  25. “Radial Velocity” Definition • Radial velocity is the velocity of an object in the direction of the line of sight • In other words, the object’s speed straight towards you, or straight away from you

  26. “Radial Velocity” Definition

  27. Radial Velocity in Context • How fast is 10 m/s? 1m/s? • What RV amplitude is required to detect a Jupiter-twin? An Earth twin? • Vote for • 10 m/s • 1 m/s • 0.1 m/s • 0.01 m/s • 0.001 m/s Mayor and Queloz 1995

  28. Radial Velocity Derivation • Today we will derive the star’s line-of-sight velocity, caused by the star’s motion about planet-star common center of mass • We will assume zero eccentricity, and an edge-on orbit (i=90 and sin i = 1)

  29. Animation • http://astro.unl.edu/classaction/animations/light/radialvelocitydemo.html • http://astro.unl.edu/classaction/animations/extrasolarplanets/radialvelocitysimulator.html

  30. RV Lecture Contents • Radial Velocity Definition • Planet Mass Derivation • Tour of Radial Velocity Curves • Measuring Planet Masses • Controversial RV Planet Detections

  31. Planet Mass Derivation • We start with an equation for the line-of-sight velocity of the star--the observable • K is called the radial velocity amplitude • The planet and star are orbiting their common center of mass

  32. Center of Mass m1r1 = m2r2 http://csep10.phys.utk.edu/astr162/lect/binaries/astrometric.html

  33. Planet Mass Derivation Star velocity K the variable arbitrarily assigned to the star velocity Center of mass Definition Kepler’s Third Law How many equations and how many unknown variables? Assume the period is known from the observations

  34. Planet Mass Derivation • From last page • Sub above into Kepler’s Third Law • Sub above into v = K =2a/P • Algebra to get mp using mp << m*

  35. Planet Mass Derivation • Here is the planet mass formula for a planet on an eccentric orbit with an orbital inclination away from edge-on.

  36. Minimum Mass Concept • Minimum mass concept • http://www.daviddarling.info/encyclopedia/R/radial_velocity_method.html

  37. RV Lecture Contents • Radial Velocity Definition • Planet Mass Derivation • Tour of Radial Velocity Curves • Measuring Planet Masses • Controversial RV Planet Detections

  38. Example 1 Courtesy G. Torres

  39. Example 1 • M dwarf star eclipsing another star • Period = 3.80 days Courtesy G. Torres

  40. Example 2 Lopez-Morales 2005

  41. Example 2 • Eclipsing binary star • Each star is M* ~ 0.6 Msun • P = 0.488 days http://www.sumanasinc.com/webcontent/anisamples/RadialVelocityCurve.html Lopez-Morales 2005

  42. Example 3 Rivera et al. ApJ, 2005

  43. Example 3 • GJ876 b and c • Notice the “glitches” • The planets are interacting and one has changing orbital parameters Rivera et al. ApJ, 2005 www.exoplanets.org

  44. Example 4 Rivera et al. ApJ, 2005

  45. Example 4 • GJ 876d a 7.5 M planet • Discovered after GJ 876b and c • A three-planet system; one we modeled during the first class • Shown are the three planets from examples 3 and 4 Rivera et al. ApJ, 2005

  46. Example 5 Butler et al. 1996

  47. Example 6 Butler et al. 2996

  48. Examples 5 and 6 • Ups And • A 3-planet system • One we modeled for the first class Butler et al. 1996

  49. Example 7