Evolutionary Models of Extra-Solar Giant Planets and Brown Dwarfs
Steward Observatory, Univ. of Arizona
With the discovery of the companions of 51 Peg, 55 Cnc, Tau Boo, Upsilon And, 70 Vir, 47 UMa, and Gl 229, evolutionary and spectral models of gas giants and/or brown dwarfs with masses from 0.3 through 60 times that of Jupiter assume a new and central role in the emerging field of extra-solar planetary studies. In this contribution, I describe the structural, atmospheric, and evolutionary characteristics of such exotic objects, as determined by our recent theoretical calculations (Burrows et al. 1995; Guillot et al. 1996; Saumon et al. 1996; Marley et al. 1996). The issue, in part diversionary, of what distinguishes a brown dwarf from a giant planet will be addressed, as will the luminosities, effective temperatures, gravities, colors, and spectral signatures of these beasts as a function of age and mass. Our theoretical calculations can be used to establish direct search strategies via SIRTF, ISO, and HST (NICMOS), and via various ground-based adaptive optics and interferometric platforms planned for the near future.