Exoplanet Discovery Joshua Pepper Vanderbilt University Keivan Stassun, Rob Siverd, Leslie Hebb, Phil Cargile - Vanderbilt University Rudi Kuhn – The University of Cape Town Scott Gaudi, Thomas Beatty – The Ohio State University

Summary Historical background How do we find exoplanets? Current state of discovery The KELT project

A New Field of Exploration Other Galaxies – 1920s Wikimedia Commons Quasars and Black Holes – 1960s-1970s Cosmic Microwave Background – 1970s-1990s

How did we get here? Most of modern history 9…(or 8) planets Now… planets

The Olden Days (pre-1992) All the planets in the Universe… Known since ancient times

Explosion of Discovery

A New Field of Exploration Dust grains → Brown Dwarfs Sizes: m → 10 7 m Masses: few thousand atoms → 0.08M Sun

Discovery Methods Microlensing Astrometry Direct Imaging Radial-Velocity Transits Background star (source) Foreground star with planet (lens) From Beaulieu, et al. 2006, Nature, 439, 437

Shift due to terrestrial planet is one microarcsecond 1,000,000 times smaller than the size of the star itself Discovery Methods Microlensing Astrometry Direct Imaging Radial-Velocity Transits

NASA, ESA, P. Kalas, J. Graham, E. Chiang, E. Kite (University of California, Berkeley), M. Clampin (NASA Goddard Space Flight Center), M. Fitzgerald (Lawrence Livermore National Laboratory), and K. Stapelfeldt and J. Krist (NASA Jet Propulsion Laboratory) Discovery Methods Microlensing Astrometry Direct Imaging Radial-Velocity Transits Seeing the Earth around the Sun: 10,000,000,000 to 1

Radial Velocity motion of the sun due to the Earth is 10 cm per second, 0.22 mph. Discovery Methods Microlensing Astrometry Direct Imaging Radial-Velocity Transits From Bouchy, et al., 2005, A&A, 444, L15

Transits planet diameter brightness time ~1%

Transit False Positives Astrophysical configurations masquerading as transits Grazing binary Blended binary 1% 10% flux

Transit False Positives Astrophysical configurations masquerading as transits 1% Main Sequence primary; late-type secondary flux

Finding Transits 1.Monitor all stars and derive lightcurves 2.Search for transit like behavior (computing- intensive!) 3.Do follow-up observations to eliminate false positives 4.Confirm planets with full dynamical information

Hot Jupiters Eccentric and inclined orbits New Planet types Puffy giants / Dense giants Ice and ocean worlds Super-Earths – metal/gas or water? Exciting systems –Binary planets –Free floating –Planets in habitable zone, >100 from Kepler already Discovery Highlights planet scattering is common

Discovery Highlights Planet Demographics from Kepler (only for Period < 50 days!) –Metallicity trend holds for gas giants but not Neptunes or terrestrial planets –Neptunes and Super-Earths are common, 30% to 50% of sunlike stars have them –Planets come in packs –Frequency is inversely proportional to stellar mass

Directions for Future Discovery 729 planets discovered (and confirmed) Two directions for future discovery –Rare, extreme, or valuable –General demographics Verify theories of formation & evolution

KELT: The Kilodegree Extremely Little Telescope 2 Fully Robotic telescopes 4k x 4k CCD, 9 micron pixels 4.5 cm aperture 26 x 26 degree field of view $60,000 per telescope

KELT: The Kilodegree Extremely Little Telescope KELT-South Deployed 2009 to Sutherland, South Africa Operated by Vanderbilt, Fisk University, and the University of Cape Town KELT-North Deployed 2005 to Winer Observatory, AZ Operated by Ohio State and Vanderbilt

Fields Observed by KELT Blue line – Galactic plane 42% of the sky Green line – ecliptic 5 years of data 1.5 years of data

Discovery Space for KELT Bright (8 < V < 11) stars with transiting planets Opportunity for followup investigations –Break msin(i) degeneracy, get mass and inclination –Planet Radius  density  composition / core mass –Atmosphere Transmission spectroscopy Emission spectroscopy –Spin-orbit alignment (Rossiter-McLaughlin effect) –Moons & Rings

How large is 26 degrees, really? 23” x 23” pixels 26 degrees

Photometric Precision

Current Status Test sensitivity by injecting transit signals into KELT data Recover 70% of injected transits for: 1 < P < 10 days depth of 0.5% to 2% (Saturn to Jupiter sizes) Current followup ongoing –eliminate false positives –confirm candidates

Image Stability

Blind Recovery of Known Planets XO-1b V = 11.3 R p = 1.12 R J P = 3.94 days

Blind Recovery of Known Planets HD189733b V = 7.67 R p = 1.18 R J P = 2.22 days

A transit survey and…comets?

Comet Schwassmann-Wachmann-1 A transit survey and…comets?

KELT Research Program Primary Science – Bright transiting planets Secondary Science – Variable stars, especially eclipsing binaries – Solar system science – Combination with other transit surveys

KELT-South Telescope