Spitzer Space Telescope - General Observer Proposal #80179


Weather on Other Worlds: A Survey of Cloud-Induced Variability in Brown Dwarfs

Principal Investigator: Stanimir Metchev
           Institution: State University of New York, Stony Brook

     Technical Contact: Daniel Apai, University of Arizona, USA
 

Co-Investigators: 
Jacqueline Radigan, University of Toronto, Canada                     
Adam Burgasser, University of California, San Diego, USA              
Etienne Artigau, University of Montreal, Canada                       
Mark Marley, NASA Ames Research Center, USA                           
Peter Plavchan, Caltech/IPAC, USA                                     
Bertrand Goldman, Max-Planck Institut fur Astronomie, Germany         
Kerstin Geissler, SUNY Stony Brook, USA                               
Ray Jayawardhana, University of Toronto, Canada                       

Science Category: brown dwarfs/very low mass stars 
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 873.0 

Abstract:
We propose a comprehensive program to detect periodic brightness variations in L
and T dwarfs caused by the spatially inhomogeneous distribution of dusty
clouds--weather patterns--in their atmospheres. We will seek trends over a broad
set of substellar characteristics, encompassing objects with a range of
temperatures, colors, and ages. While numerous variability searches have been
conducted on L and T dwarfs to date, the vast majority have been ground-based
and limited in precision. Only recently did members of the presently assembled
team produce clear and repeatable detections of periodic flux variations in a
half dozen substellar objects, thus providing the first strong evidence for
heterogeneous cloud cover in their atmospheres. Spitzer's factor of 3-5 superior
photometric precision enables a much more sensitive and comprehensive study of
the atmospheric dynamics underlying the phenomenon. Our program will increase
the scope of mid-infrared variability studies of brown dwarfs by more than an
order of magnitude. We will target 44 ultra-cool dwarfs with spectral types
between L3-T8, spanning the full color range at each spectral subtype, and
including both low-gravity and field objects. We anticipate significant
detections of periodicities as small as 10 milli-magnitudes in amplitude, which
will enable the routine detection of weather patterns smaller than Jupiter's
Great Red Spot on extrasolar substellar objects. The presence and brightness
temperature distribution of these weather patterns will be analyzed in the
context of state-of-the-art cloudy atmospheric models, and will reveal the
longitudinal and vertical thermodynamics of substellar atmospheres. The proposed
program will be relevant to the broader understanding of rotating,
low-temperature, brown dwarf and exoplanetary atmospheres: a regime entirely
different from that of the irradiated hot-Jupiter type extrasolar planets
studied with Spitzer to date.