Modeling the infrared spectrum of the earth-moon system: Implications for the detection and characterization of earthlike extrasolar planets and their moonlike companions

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21 Scopus citations

Abstract

The Moon maintains large surface temperatures on its illuminated hemisphere and can contribute significant amounts of flux to spatially unresolved thermal infrared (IR) observations of the Earth-Moon system, especially at wavelengths where Earth's atmosphere is absorbing. In this paper we investigate the effects of an unresolved companion on IR observations of Earthlike exoplanets. For an extrasolar twin Earth-Moon system observed at full phase at IR wavelengths, the Moon consistently comprises about 20% of the total signal, approaches 30% of the signal in the 9.6μm ozone band and the 15μm carbon dioxide band, makes up as much as 80% of the signal in the 6.3μm water band, and more than 90% of the signal in the 4.3μm carbon dioxide band. These excesses translate to inferred brightness temperatures for Earth that are too large by 20-40 K and demonstrate that the presence of undetected satellites can have significant impacts on the spectroscopic characterization of exoplanets. The thermal flux contribution from an airless companion depends strongly on phase, implying that observations of exoplanets should be taken when the star-planet-observer angle (i.e., phase angle) is as large as feasibly possible if contributions from companions are to be minimized. We show that, by differencing IR observations of an Earth twin with a companion taken at both gibbous and crescent phases, Moonlike satellites may be detectable by future exoplanet characterization missions for a wide range of system inclinations.

Original languageEnglish (US)
Article number51
JournalAstrophysical Journal
Volume741
Issue number1
DOIs
StatePublished - Nov 1 2011
Externally publishedYes

Keywords

  • astrobiology
  • Earth
  • infrared: planetary systems
  • Moon
  • planets and satellites: detection
  • techniques: miscellaneous

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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