TPF-I SWG Report - Exoplanet Exploration Program - NASA

I NTRODUCTION
1 Introduction
Over 200 planets with masses ranging from the deuterium-burning limit of 13 Jupiter masses (M Jup ) down
to 5.5 Earth masses (M ⊕ ) have been detected through changes in the radial velocity or position of host
stars, or through changes in the brightness of host stars due to transits or microlensing. These planets are
found in orbits ranging from inside 0.05 astronomical units (AU) out to 5 AU with a wide range of orbital
eccentricities. The physical characterization of a few of these planets has already begun with the detection
at infrared wavelengths by the Spitzer Space Telescope of the secondary transits of three “Hot Jupiters”
and the monitoring of the light curve of the “Hot Jupiter” companion of υ Andromedae (Figure 1-1).
These results constrain the temperature, radius, and albedo of the planets and enable the study of the
rotation and weather on distant planets.
But much more is possible beyond these initial measurements. The interferometric version of the
Terrestrial Planet Finder (TPF-I) described in this report (Figure 1-2) will extend this measurement
capability by many orders of magnitude, enabling the study of terrestrial planets in the Habitable Zone
(1 AU from a G2V star) as well as to gas or icy giant planets out to 5 AU. TPF-I is currently envisioned
Figure 1-1. The Spitzer telescope has detected thermal emission throughout the entire 4-day period of the ‘’Hot
Jupiter’’ companion to the star Upsilon And (Harrington et al. 2006). The solid curve shows a model of a tidally
locked planet with a sub-solar point that is considerably hotter than the backside due to relatively poor global
circulation of winds. The TPF interferometer will extend these observations to Earth-sized planets in the habitable
zone of nearby stars.
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