Properties of Extrasolar Planets ASTR 241

Home , Exoplanet, Orbital eccentricity, Orbital inclination, Orbital period, Transit (astronomy)

Artist Impression: NASA Properties of Solar System Planets

Terrestrial Planets Jovian Planets General Properties small size and mass large size and mass nearly circular orbits high density low density nearly all angular momenta vectors aligned

rock & metal H, He, H20, CH4, NH3, … “debris” - astroids, Kuiper belt, Oort Cloud solid surface no solid surface few moons, no rings many moons, no rings close to sun, warm far from sun, warm Conﬁrmed Planets - 2013

Transits RV Microlensing Imaging

Solar System Pulsar Timing

Data: exoplanets.org Exoplanet Detection Methods (planet = extrasolar planet = exoplanet)

Doppler Method Transit Method v How Do We Detect Exoplanets? radial = c

Method #1: Doppler Method Movie credit: ESO Mauna Kea Observatories

Photo credit: Richard Wainscoat/Gemini Observatory/AURA/NSF Jupiter’s Doppler Signal

Away from us 13 meters per Orbit Period second!

Planet Mass Meters per second

Toward us What We Found

4.2 days! 0.45 Jupiter masses Meters per second

51 Pegasi Hot Jupiter

1% of Sun-like stars have one Image: NASA Determination of Orbital Distance ! from Star to Planet

Period = 4.2 days! ! Kepler’s 3rd Law: P2 = a3! ! Units: P in years, a in AU! ! Solve for a:! a = 0.05 AU! ! Proximity: Temp = 1800 C Determination of Planet’s Mass

Conservation of Momentum: ! momentum of star = momentum of planet! ! MSTAR VSTAR = Mplanet Vplanet

Solve for Mass of planet:! Mplanet = MSTAR VSTAR / Vplanet

MSTAR : Star Masses are known ! (most are Sun-like)

VSTAR from Doppler shift (semi-amplitude): ! 55 m/s

What is Vplanet ?

Vplanet = 2 π a / P! You know “a” from Kepler’s 3rd Law: P2 = a3

Can Determine Mplanet Mercury’s Orbit orbital distance = 0.39 AU! Temp = 800 degrees

51 Peg b’s Orbit orbital distance = 0.05 AU! Temp = 1,800 degrees Semi-major Axes (Orbital Distances) for Jovian Planets

~20% of Sun-like stars have a giant planet orbiting within 10 AU Orbital Eccentricities of Jovian Planets e = 0.01 e = 0.06 e = 0.05 e = 0.02

Orbital Eccentricity Giant Planet-Metallicity Correlation Fischer and Valenti (2004) Valenti Fischerand

Giant Planets are more common around stars rich in metals! This is a clue to planet formation! Systems of Planets

Four-piter

Two-piter

Dinky Doppler Method of Planet Detection

Measurable quantities planet mass ( M sin(i) ) orbital period (P) → semi-major axis (a) orbital eccentricity (e) orbital inclination (in some cases) planet multiplicity (# of planets per star) infer planet temperature host star properties (temperature, gravity, metal content) How Do We Detect Exoplanets? Method #2:

Transit Method Question for Students:

How big is the planet?

2 π R planet 2 π R star Transit Method of Planet Detection

Measurable quantities planet size ( radius ) orbital period → semi-major axis orbital eccentricity (in exceptional cases) planet multiplicity dynamical interactions between planets infer planet temperature atmospheric properties Kepler: A Mission to Find EarthsTransit Example

Image: NASA

Kepler-10 Light Curve

24 Kepler-10 Light Curve Period = 45.29 days

25 Kepler-10 Light Curve Period = 45.29 days

26 Period = 45.29 days Kepler-10 Light Curve Period = 45.29 days Kepler-10 Light Curve

Period = 0.84 days Kepler-10 Light Curve Batalha et al. (2011) al. et Batalha

Transit Depth: 0.00015

Kepler-10b

Radius = 1.4 Rearth Period = 0.83 days Planet Size and Mass Distributions

Small planets are ubiquitous!

Most stars have close-in “super-Earth” Planets!

Why doesn’t the Solar System have a super-Earth? Known Planets - Masses and Radii

Howard et al. 2013 (Nature) Possible Compositions for super-Earth Planets

Different admixtures of H/He, water, rock, iron Planet Density Distribution Weiss & Weiss

Planets Larger than ~1.5X Earth-size are low density. Smaller planets are high density. Kepler-78b - A Planet the Size and Mass of Earth

Howard et al. 2013 (Nature) Multiple Planets Orbiting the Same Star are Common Our Solar System Video: Dan Fabrycky What about Earth-like Planets

Image: NASA

Kepler-186

Credit: NASA Image: NASA Erik Petigura Exoplanet Atmospheres

Planets have slightly different sizes when measured at different wavelengths because of their atmospheres Properties of Solar System Planets

Terrestrial Planets Jovian Planets General Properties small size and mass large size and mass nearly circular orbits high density low density nearly all angular momenta vectors aligned rock & metal H, He, H20, CH4, NH3, … “debris” - astroids, Kuiper belt, Oort Cloud solid surface no solid surface few moons, no rings many moons, no rings close to sun, warm far from sun, warm

Properties of Extrasolar Planets

Terrestrial Planets Intermediate Planets Jovian Planets they exist! “super-Earths” or “sub-Neptunes” large size and mass small size and mass ubiquitous! low density

high density common < 1 AU, maybe > 1AU H, He, H20, CH4, NH3, … rock & metal (probably) low eccentricity orbits no solid surface solid surface (probably) “ﬂat” planetary systems (not-tilted orbits) moons? rings? moons?, rings? all orbital distances common < 1 AU, maybe > 1AU all eccentricities low eccentricities many in tilted orbits prefer metal-rich stars Measurable Properties of Extrasolar Planets

Doppler Method Transit Method planet mass ( M sin(i) ) planet size ( radius ) orbital period -> semi-major axis orbital period -> semi-major axis orbital eccentricity orbital eccentricity (in exceptional cases) orbital inclination (in some cases) planet multiplicity planet multiplicity dynamical interactions between planets infer planet temperature infer planet temperature host star properties (Temp, grav., metal content) atmospheric properties

Properties of Extrasolar Planets

Terrestrial Planets Intermediate Planets Jovian Planets they exist! “super-Earths” or “sub-Neptunes” large size and mass small size and mass ubiquitous! low density