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Lecture-15 (PDF) Northeastern Illinois University Other Solar Systems Greg Anderson Department of Physics & Astronomy Northeastern Illinois University Winter-Spring 2020 c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 1 / 53 Northeastern Illinois Outline University Other Solar Systems Detection Exoplanets Earth Like Planets Nebular Theory Revisited Review c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 2 / 53 Northeastern Illinois University Outline Other Solar Systems Exoplanets are Common Exoplanets Discovery Zone Detection Exoplanets Earth Like Other Solar Systems Planets Nebular Theory Revisited Review c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 3 / 53 Northeastern Illinois Exoplanets are Common University Exoplanet: a planet that orbits a star outside the solar system. • Gravitational microlensing studies suggest Milky Way stars host, on average, one or more planets in a distance range of 0.5 – 10 AU. • One in five stars similiar to our Sun have an Earth sized planet in the habital zone. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 4 / 53 Northeastern Illinois Exoplanets University NASA’s Exoplanet Archive, as of February 2019: • 4,770 candidates • 3,917 confirmed exoplanets • 657 multi-planet systems • 361 confirmed & in habitable zone Exoplanet Graphics: For recent results see: • Mass vs. Distance • NASA’s Exoplanet Archive • Planetary Temperatures • Exoplanets.org • Number vs. Size • Exoplanet.eu c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 5 / 53 Northeastern Illinois University Outline Other Solar Systems Detection Finding Exoplanets NASA Kepler Spacecraft TESS Five Discovery Methods Detection vs. t Detection Discovery Techniques Transit Photometry Transit Light Curves Doppler Shift Direct Imaging Disks Microlensing Exoplanet Microlensing Astrometry Exoplanets Earth Like Planets Nebular Theory Revisited c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 7 / 53 Northeastern Illinois Finding Exoplanets University “Looking for an Earth-like planet around a nearby star is like standing on the East Coast of the United States and looking for a pinhead on the West Coast - with a VERY bright grapefruit nearby.” • Kepler Space Telescope (2009-2013) c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 8 / 53 Northeastern Illinois TESS University Transiting Exoplanet Survey Satellite (TESS) • Launched April 18, 2018. • Two-year survey of over 200,000 stars. • Expected to to discover thousands of exoplanets. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 10 / 53 Northeastern Illinois Five Discovery Methods University Transit: Searching for shadows – a star’s brightness drops when a planet crosses in front. Radial velocity: Watching for wobble – aka Doppler Spectroscopy. Detect Doppler shift in stars as in orbits center of mass. We can detect ∆v ∼> 1 m/s. Direct imaging: Taking pictures – Currently IR, large planets, far from star. Gravitational microlensing: The gravitational field of a star or planet acts as a lens to magnify the light of more distant objects. Astrometry: Precise measurements of the positions and movements of stars. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 11 / 53 Northeastern Illinois Discovery Techniques University Method Number of Planets Transits 3144 Radial Velocity 793 Imaging 49 Microlensing 86 Astrometric 1 Total 4126 For updated counts please consult the NASA Exoplanet Archive. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 13 / 53 Northeastern Illinois Transit Photometry University Transit: when one celestial body appears to move across the face of another. star planet Brightness Time c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 14 / 53 llustration from Bill Borucki’s Jan 2010 AAS Presentation b b b b b b b b b b b b b b b Doppler Shift due to Stellar Wobble b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b Mt. Palomar’s Hale Telescope: Star HR8799, and three planets. 120 ly distant. Northeastern Illinois Disks Around β Pictoris University c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 18 / 53 Northeastern Illinois University Outline Other Solar Systems Detection Exoplanets XKCD Kepler Planet Candidates Eccentricity vs. Period Mass vs. Period Exoplanets Radius vs. Period Irradiation vs. Period Earth Like Planets Nebular Theory Revisited Review c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 22 / 53 http://xkcd.com/1071/ Northeastern Illinois University Outline Other Solar Systems Detection Exoplanets Earth Like Planets Habitable Zone Kepler-186f ESI Earth Like Planets Habitable Zone Planets HEC Poster Nearest Confirmed Exoplanets Nebular Theory Revisited Review c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 29 / 53 Northeastern Illinois Kepler-186f University The first known Earth-size exoplanet to lie within a habitable zone. Red dwarf star Kepler-186. d = 490 ly. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 31 / 53 Northeastern Illinois Earth Similarity Index (0 ≤ ESI ≤ 1) University Not Earth Like Venus Mars Earth Mercury Kepler-438b 0 0.2 0.4 0.6 0.8 1.0 KOI-433.02 m n x − x wi/n ESI = 1 − i io =1 xi + xio Yi Property Referencevalue xio weight wi Radius r⊕ 0.57 Density ρ⊕ 1.07 Escape velocity v⊕ 0.70 Surface Temp 288 K 5.58 There is not a scientific concensus advocating use of the ESI. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 32 / 53 Northeastern Illinois Nearest Confirmed Exoplanets University 5 data source 4 3 2 1 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Distance (ly) c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 35 / 53 Northeastern Illinois University Outline Other Solar Systems Detection Exoplanets Earth Like Planets Nebular Theory Revisited Nebular Theory Nebular Theory Frost Line Hot Jupiter Revisited Hot Jupiter Hot Jupiters Challenges Planetary Migration Migrations Late Heavy Bombardment Further Study Review c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 36 / 53 Northeastern Illinois Nebular Theory University Nebular Theory: Kant 1755, Laplace 1795 Our solar system formed from a giant cloud (nebula) of interstellar gas and dust. Denser regions of the solar nebula experienced stronger gravity and begin gravitational contraction. Heating, Spinning, Flattening • The Rotational speed of cloud increased as it contracted due to conservation of angular momentum: • Collisions between particles in the collapsing nebula flattened it into a flat disk with circular orbits. • The nebula temperature increased as it collapsed due to conservation of energy As the protoplanetary disk cooled, metal, rock and ice condense, coagulate and accrete into planetesimals and then planets. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 37 / 53 TFrost ≈ 150 K T >TF T = TF T <TF aFrost ≈ 5 AU b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b Frostb Line b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b
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