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Home , 51 Pegasi, HD 209458, HR 8799, Kepler space telescope

Exoplanets

Transient and Differential

Edge on Face on Lab 5: Detecting Exoplanet Lab 5: Detecting Exoplanet Transit • Due: March 6 (Monday) 4:09pm (before the class) • Target: GJ 1214 b • Data: from ACAM on the William Herschel • Lectures on and Differential Photometry • Group Presentations: Feb 13 and 27 • Feb 13 class: starts at 5:10pm (lab from 4:10pm) • Feb 13 group discussion: - 4 minutes for presentation; 1 minute for Q/A - should include 3 slides for summarizing the the detailed steps of Lab 5 - should include your results by the key step #2

• Class dinner sometime in March after class Exoplanets

Extra- (Exoplanets)  How Do We Detect? Exoplanet discoveries per

2,000 confirmed exoplanets discovered so far! Exoplanets

So how do we detect them?

● Direct Imaging ● Stellar Motions − velocities, timing, ● Light curve − transient planets Direct Imaging

• Currently heating up with , high contrast imaging systems • -like around a -like is 10 billion times fainter than its star • Need to find a faint object very close to a bright star

Beta Pictoris

HR 8799 Direct Imaging

• Only about ~ 20 planets directly imaged • Technically challenging Stellar Motions

• , timing, astrometry Stellar Motions Radial Velocity Comparisons

1995

• Best measurements now measure variations of 0.5 m/s (a slow walk) Stellar Motions Radial Velocity Comparisons

• b – First planet around sun-like star • P = 4.23 days! -> Hot Exoplanets How do we detect exoplanets? Light Curve Method: Transient Planets A transient planet changes blocks the light from a star = eclipse!

● Eclipse depth in terms of planet and star radii (for circular )?

● Transit probability in terms of star radius and distance between the planet and star (for circular orbit)? Light Curve – Transiting Planets

HD 209458

Transit Transit

Secondary Eclipse

Orbital Period

Can reach 10 parts-per-million accuracy for the brightest from space Exoplanets How do we detect exoplanets? Light Curve Method: Transient Planets A transient planet changes blocks the light from a star = eclipse!

“Challenges and Advantages of Detecting Transient Planets?” Exoplanets How do we detect exoplanets? Light Curve Method: Transient Planets

Large Transit Planet Survey: OGLE, , Corot, … Exoplanets How do we detect exoplanets? Transient Planets The Kepler Project

The Kepler Mission: Field

FOV The Kepler Mission The Kepler Mission The Kepler Mission Exoplanets How do we detect exoplanets? Transient Planets

Example: HD209458b (1999) Small telescope discovery

Hubble data Density measurement Density measurement: Example Kepler-78

Star KIC 8435766 (Kepler-78) h m s (α) 19 34 58 (δ) +44°26′ 54″

Apparent magnitude (mV) 12

Radius (r) 0.73±0.15 R☉ Temperature (T) 5143 (±70) K [Fe/H] -0.08 (±0.13) A planet was discovered in 2013 by analyzing data from Kepler space telescope. The planet was found not only transiting the star, but its and reflected light from the parent star due to orbital phases were also detected. Density measurement: Example

Kepler-78b (formerly known as KIC 8435766 b) is an exoplanet orbiting around the star Kepler-78.

Mass (m) 1.69-1.85 M⊕

Radius (r) 1.12 R⊕

Bond Albedo (%) 20-60 %

-3 Density (ρ) 5.3-5.6 g cm So how de we measure the density of exoplanets? Let’s look into more!

What do we know from transit light curves?

• Transit Depth • Transit Duration • Transit Period • Ingress and Egress Times

Sky-projected distance between the center of the star and planet. The total transit duration is heavily dependent on the impact parameter.

Ingress Egress

Transit Depth

Limb Darkening

Primary and Secondary Eclipses