Spitzer Space Telescope - Directors Discretionary Time Proposal #258


Infrared Photometry of the Hot Earth Orbiting Gliese 876

Principal Investigator: Drake Deming
           Institution: NASA's Godddard Space Flight Center

Co-Investigators: 
Sara Seager, Carnegie DTM                                             

Science Category: extrasolar planets 
 Observing Modes: IracMap 
  Hours Approved: 8.6 

Abstract:
Rivera et al.  (2005) have recently reported Doppler detection of a
~7.5 Earth-mass planet orbiting the nearby M-dwarf Gliese 876 with a
period of 1.97 days.  We propose to detect the phase variation of the
IR thermal emission of this planet, using IRAC at 8 and 4.5 microns.
Because this system lies only 4.7 pc from Earth, the IR flux from this
terrestial planet is likely to be comparable to the thermal fluxes
from the hot Jupter planets already detected by Spitzer.  Since the
planet's rotation is likely to be synchronous with its orbit, the
amplitude and relative phase of the thermal emission curve will yield
significant information on the existence and nature of an atmosphere
on this extrasolar Earth.  Our error level will be a factor of 8 below
the maximum expected signal, and even a null result will be of
significant interest.