What Have We Found? 1978 planets in 1488 systems as of 11/15/15 ( ) 1642 planets candidates (

Transcription

1 Exoplanets. II

2 What Have We Found? 1978 planets in 1488 systems as of 11/15/15 ( ) 1642 planets candidates ( Detected by radial velocity/astrometry: 621 Transiting planets: 1230 Detected by microlensing: 41 Detected by imaging: 62 Detected by timing: 27 (some are duplicate entries)

3 Summary - Techniques Direct imaging Requires large planets far from star Requires nearby systems Best with young systems Bright hot central stars help

4 Direct Imaging Example: HR 8799

5 Why young planets are bright

6 Beta Pictoris ~9 AU from star M: ~ 7 M J P: ~20 yrs T: ~1600K

7 Summary - Techniques Direct imaging Young large planets far from nearby bright star Astrometric Wobble Requires face-on orbit; small mass ratio Depends on distance: φ = a/d

8 Review: Velocity Wobble Equal masses Earth - Moon Sun - Earth Objects orbit their mutual center of mass

9 Center of the Solar System

10 Summary - Techniques Direct imaging Young large planets far from nearby bright star Astrometric Wobble Requires face-on orbit; small mass ratio; nearby Doppler Wobble Independent of distance Sensitivity depends on inclination, mass ratio

11 First Extrasolar Planet: 51 Pegasi b Radial velocity/ Doppler Shift

12 Upsilon Andromedae Periods: 4.6, 241, 3848 days

13 Doppler Wobble: Gliese 876 The three planets of Gl 876: masses = 2.5 M J, 0.8 M J, and 7.5 M

14 Gliese 876 M4V star 3 planets, including the least massive known (0.75 M )

15 Summary - Techniques Direct imaging Young large planets far from nearby bright star Astrometric Wobble Requires face-on orbit; small mass ratio; nearby Doppler Wobble Independent of distance Sensitivity depends on inclination, mass ratio Transits Requires edge-on orbit Short periods help

16 Transit Example - Ground

17 Transit Example - Kepler

18 Summary - Techniques Direct imaging Young large planets far from nearby bright star Astrometric Wobble Requires face-on orbit; small mass ratio; nearby Doppler Wobble Independent of distance Sensitivity depends on inclination, mass ratio Transits Requires edge-on orbit, small separation Microlensing Independent of distance

19 Microlensing Example

20 OGLE 2005-BLG-390

21 Sensitivity to Exoplanets

22 Extrasolar Planet Detectability

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24 Orbital Eccentricity

25 Planetary Densities

26 Densities

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28 Extrasolar Planet Masses Earth = 0.005

29 Extrasolar Planets Planets are preferentially found around metal-rich stars - mostly younger than the Sun.

30 Metallicities updated

31 Exoplanet Summary No Solar System-like systems found Many systems more compact than SS Dominated by hot Jupiters Densities consistent with gas giants Sodium and Hydrogen have been detected Water Worlds Super-Earths Many eccentric orbits Biases are important

32 Biases Transits: large planets; periods < year Doppler Wobble: large planets very close to star Direct imaging: large young planets far from star

33 Extrasolar Planet Masses

34 Unbiased Masses

35 Tatooine

36 Exoplanet Comparison

37 How do you make a hot Jupiter? Existing picture of SS formation needs some changes Nebular theory predictions formation of other SS Suggests more planets form around metal-rich stars. Jovian planets should be far from star in circular orbits Revision Jovian planets formed far from star in circular orbits Subsequently migrated inward

38 Planetary Migration Occurs in the presence of protoplanetary disk Planet moving through disk creates density waves Waves exert gravitational force on planet Planet loses orbital energy, moves toward star Some stars show evidence of consuming planets. What about Jupiter?

39 The Planetary Shuffle Gravitational encounters eccentric orbits Two Jovian planets get close: 1 ejected, one spirals inward, elliptical orbit Small planetesimals ejected (to Oort cloud), Jovian planet loses orbital energy Happened in our SS Resonances Lead to eccentric orbits Can yield migration or ejection

40 A Model for Our Solar System Series of papers in Nature in 2005 Solar System: Sun, planets, debris disk of planetesimals Planets accrete or scatter planetesimals Angular momentum exchange causes planetary migration Jupiter moves in, Saturn, Uranus, and Neptune move out 1:2 orbital resonance between Jupiter and Saturn reached Kick in eccentricities, destabilitization of orbits Uranus and Neptune scattered outward, switch positions Small bodies move inward Interactions explain current orbital radii and eccentricities 1:2 resonance explains late heavy bombardment period Initial geometry can give resonance (and hence scattering) at right time. Asteroids will also be perturbed at this time.

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42 Extreme Planets Rare, hence need large numbers to find Opportunity to study the limits of planet formation and survival One pathological case may provide more information than many normal cases

43 KIC F star. Deep aperiodic dips, up to 20% blockage

44 HD189733b (a hot Jupiter) T ~ 3000K Winds to 5400 mph

45 55 Cnc e Brightness varied factor of 3 in 2 days

46 Other oddities Salt clouds Iron hydride precipitation Hot Jupiters Close-in multiple systems

47 Extrasolar Planetary Systems 55 Cancri (G5V): 5 planets 1 M U 0.4 AU 1 M J 0.15 AU 1 M s 0.25 AU 0.5 M J 0.8 AU 4 M J 5 AU

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