On high-contrast characterization of nearby, short-period exoplanets with giant segmented-mirror telescopes

Abstract

Measurements of the frequency with which short-period planets occur around main sequence stars allows a direct prediction of the number and types of such planets that will be amenable to characterization by high-contrast instruments on future giant segmentedmirror telescopes (GSMTs). Adopting conservative assumptions, I predict of order 10 planets with radii R P = 1−8 R ⊕ and equilibrium temperatures 400 K should be accessible around stars within 8 pc of the Sun. These numbers are roughly the same for both nearinfrared observations of scattered starlight and mid-infrared observations of planetary thermal emission, with the latter observations demonstrating greater relative sensitivity to smaller and cooler planets. Adopting the conservative assumption that planets with R P = 1−2 R ⊕ and 2−4 R ⊕ occur with equal frequency, I predict a 40% chance that a planet with R P = 1−2 R ⊕ and equilibrium temperature 200-250 K will accessible to high-contrast thermal infrared characterization; this would be a compelling object for further study. To validate these predictions, more detailed analyses are needed of the occurrence frequencies of low-mass planets around M dwarfs, both in the Kepler field and in the solar neighborhood. Several planets already discovered by radial velocity surveys will be accessible to near-infrared high-contrast GSMT observations, including the low-mass planets α Cen Bb and (depending on their albedos) GJ 139c and d, GJ 876b and c, and τ Cet b, c, and d; τ Cet f would be amenable to thermal infrared characterization. Further efforts to model the near-infrared reflectance and mid-infrared emission of these and other short-period planets are clearly warranted, and will pave the way for the interpretation of future high-contrast characterization of a variety of planets around the nearest stars.

Direct detection of exoplanets in the 3–10 μm range with E-ELT/METIS

“…Unlike in the subsection 'Direct detection of planets found by RV surveys', here the planet's thermal Table 2. Compared to the original study done by Crossfield (2013), which had the goal of comparing the expected detection yield of different wavelength regimes, instrument performances and telescope sizes, the present study is different in a number of aspects. All values were adopted from the exoplanet.eu database (unless indicated otherwise) except for the apparent L magnitude and the M band flag, which were derived here (see the subsection 'Direct detection of planets found by RV surveys') a Flag indicating whether object is also detected in the M band within the given detection limits.…”

“…To do this we used the Monte Carlo approach outlined in detail in Crossfield (2013). To do this we used the Monte Carlo approach outlined in detail in Crossfield (2013).…”

“…Briefly described, this analysis simulates thousands of plausible extrasolar planetary systems using measurements of planet frequency from the Kepler satellite (Howard et al 2012) and estimates the likelihood of finding a detectable planet by comparing the planets' predicted blackbody fluxes to analytic estimates of high-contrast performance (Guyon 2005) and detection limits. For this, the planet's bond albedo and geometric albedo are assumed to be wavelength independent and are randomly drawn from a uniform distribution between 0.0 and 0.4 (Crossfield 2013). Key properties of planets detected by RV surveys that can be imaged with E-ELT/METIS (see text for selection criteria).…”

“…Key properties of planets detected by RV surveys that can be imaged with E-ELT/METIS (see text for selection criteria). Crossfield (2013) focused primarily on contrast performance and did not explicitly include constraints coming from sensitivity estimates. b L band brightness likely underestimated as first-order estimates suggest T eff , model < T eq (see text).…”

The Thirty Meter Telescope International Observatory Facilitating Transformative Astrophysical Science

“…The 10 m class telescopes have been used to conduct rudimentary studies of the atmospheres of a few of the closest, recently formed hot Jupiter planets 13 . Space telescopes have been able to coarsely map the surface temperature distribution of lava rock planets 14 . To be able to characterize low-mass, cool, mature, earth-like planets in the habitable zones of their host stars we need the high spatial resolution, high contrast and sensitivity provided by the TMT.…”