Exoplanet Discovery

Joshua PepperVanderbilt University

Keivan Stassun, Rob Siverd, Leslie Hebb, Phil Cargile - Vanderbilt UniversityRudi 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

http://www.fas.org/irp/imint/docs/rst/Sect20/A6.html

Cosmic Microwave Background – 1970s-1990s

http://www.space.com/bestimg/?guid=4499b3474b769&cat=strangest

How did we get here?

Most of modern history

9…(or 8) planets

Now… 8 + 729 planets

The Olden Days (pre-1992)

All the planets in the Universe…

Known since ancient times 1781 1846 1930

Explosion of Discovery

1700 1800 1900 2000

5

10

8 + 729

A New Field of Exploration

Dust grains → Brown Dwarfs

Sizes: 10-7 m → 107 m Masses: few thousand atoms → 0.08MSun

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 microarcsecond1,000,000 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

• TransitsFrom Bouchy, et al., 2005, A&A, 444, L15

Transits

planet diameter

brig

htne

ss

time

~1%

Finding Transits

1. Monitor all stars and derive lightcurves2. Search for transit like behavior (computing-

intensive!)3. Do follow-up observations to eliminate false

positives4. 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 Highlightsplanet 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-SouthDeployed 2009 to Sutherland, South Africa

Operated by Vanderbilt, Fisk University, and the University of Cape Town

KELT-NorthDeployed 2005 to Winer Observatory, AZ

Operated by Ohio State and Vanderbilt

Fields Observed by KELT

Blue line – Galactic plane 42% of the skyGreen line – ecliptic

5 years of data

1.5 years of data

Discovery Space for KELTBright (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

Blind Recovery of Known Planets

HD189733b

V = 7.67Rp = 1.18 RJ

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