Direct Imaging in the Habitable Zone and the Problem of Orbital Motion

Abstract

High contrast imaging searches for exoplanets have been conducted on 2.4-10 m telescopes, typically at H band (1.6 microns) and used exposure times of ~1 hr to search for planets with semi-major axes of > ~10 AU. We are beginning to plan for surveys using extreme-AO systems on the next generation of 30-meter class telescopes, where we hope to begin probing the habitable zones (HZs) of nearby stars. Here we highlight a heretofore ignorable problem in direct imaging: planets orbit their stars. Under the parameters of current surveys, orbital motion is negligible over the duration of a typical observation. However, this motion is not negligible when using large diameter telescopes to observe at relatively close stellar distances (1-10pc), over the long exposure times (10-20 hrs) necessary for direct detection of older planets in the HZ. We show that this motion will limit our achievable signal-to-noise ratio and degrade observational completeness. Even on current 8m class telescopes, orbital motion will need to be accounted for in an attempt to detect HZ planets around the nearest sun-like stars alpha Cen A & B, a binary system now known to harbor at least one planet. Here we derive some basic tools for analyzing this problem, and ultimately show that the prospects are good for de-orbiting a series of shorter exposures to correct for orbital motion.

33 pages, 10 figures, accepted to ApJS

References in corpus (7)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• Habitable Zones Around Main-Sequence Stars: New Estimates
• Optical Images of an Exosolar Planet 25 Light Years from Earth
• The Gemini Deep Planet Survey -- GDPS
• The impact of red noise in radial velocity planet searches: Only three planets orbiting GJ581?
• Confidence Level and Sensitivity Limits in High Contrast Imaging
• The Lyot Project Direct Imaging Survey of Substellar Companions: Statistical Analysis and Information from Nondetections

Cited by in corpus (7)

• Imaging low-mass planets within the habitable zone of α Centauri
• Deep orbital search for additional planets in the HR 8799 system
• K-Stacker: Keplerian image recombination for the direct detection of exoplanets
• Direct imaging of exoplanets in the habitable zone with adaptive optics
• Orbital Differential Imaging: A New High-Contrast Post-Processing Technique For Direct Imaging of Exoplanets
• A Deep Search for Additional Satellites around the Dwarf Planet Haumea
• PACOME: Optimal multi-epoch combination of direct imaging observations for joint exoplanet detection and orbit estimation