Spitzer Space Telescope - General Observer Proposal #30498


Spitzer Characterization of Super Earths

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

Co-Investigators: 
Sara Seager, Carnegie Institution of Washington                       

Science Category: extrasolar planets 
 Observing Modes: IracMap 
  Hours Approved: 12.0 

Abstract:
We propose to characterize super-Earth-mass planets around nearby „and
infrared bright„ low-mass stars.  We define super Earths to be planets
between 5 and 30  Earth masses (and to include Neptune-mass planets).
It may seem counter-intuitive that super Earths can be studied with
Spitzer.  However, the small size of M-dwarfs and the IR brightness of
nearby M-dwarfs compensates for the small planetary radius of low-mass
planets.  We propose two related components in this program:  (1) A
search for infrared photometric orbital variation of the 7.5 Earth
mass planet Gliese 876d in IRAC 4.5 and 8 micron bands.  This will
allow us to identify the presence or absence of a thick atmosphere.
(2) Target of Opportunity observations of primary eclipse (transit)
and secondary eclipse(s) of any hot super Earths to be discovered
transiting M-dwarf stars.  The primary eclipse (at IRAC 8 micron band)
will allow a planet radius to be determined to 10% accuracy, enough to
infer the planet's bulk composition (e.g., substantial gas envelope,
liquid ocean interior, predominantly rocky or massive iron core,
etc.).  The secondary eclipse observations (in all four IRAC bands)
will allow investigation of atmospheric escape, and planetary
atmosphere composition and temperature.