Assessing the Nature and Impact of Observed Stellar Variability on Kepler’s Ability to Detect Earth-Size Planets
Abstract
The Kepler spacecraft was launched on March 6 2009 on a 3.5-year mission to determine the frequency of Earth-size and larger planets in or near the habitable zones of their stars. Kepler has been observing 160,000 stars to detect transiting planets for over two years and has discovered more than 16 confirmed or validated planets and has identified over 1200 candidate planets. There is sufficient data and experience with the photometer to characterize Kepler’s ability to detect weak signatures of small, terrestrial planets. The photometer’s sensitivity depends on the total combined differential photometric precision (CDPP) and on the mission lifetime. These driving requirements for Kepler called for a total CDPP of 20 ppm for 12th magnitude G2 dwarf stars in 6.5 hours, and a mission lifetime of 3.5 years. The noise budget includes 14 ppm for shot noise, 10 ppm for instrument noise and 10 ppm adopted for intrinsic stellar variability. The CDPP requirement was necessarily set without knowledge of actual typical levels of stellar variability. We find that Kepler’s noise metrics for 12th magnitude dwarf stars are dominated by stellar variability and the overall combined noise is ∼50% higher than the required value. While this does reduce Kepler’s ability to achieve its scientific objectives, Kepler’s originally envisioned capability to detect terrestrial planets can be recovered by extending the duration of the flight mission to 8 years.
- Publication:
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AAS/Division for Extreme Solar Systems Abstracts
- Pub Date:
- September 2011
- Bibcode:
- 2011ESS.....2.1914J