The Habitable Zones of Pre-Main-Sequence Stars

The habitable zone (HZ) is the region around a star in which liquid water could exist on a planetary surface. Although 1-D models have been traditionally employed in HZ studies, recent investigations using 3-D models incorporate more realistic physics and self-consistently calculate both the effects of clouds and relative humidity. However, both parameters remain poorly understood, especially as applied to planetary atmospheres near the inner edge of the HZ. Thus, 1-D models remain indispensable for recognizing major trends and patterns that can then be analyzed more fully with more sophisticated models. I will present an updated 1-D climate model, coupled with results from other 1-D and 3-D studies, to assess the sensitivity of our Solar System's inner edge to changes in surface relative humidity and clouds. This novel relative humidity parameterization self-consistently calculates surface relative humidity and assumes tropospheric relative humidity gradually increases with temperature. These results show that treating relative humidity more realistically moderately increases the width of the habitable zone. Lastly, I discuss certain caveats regarding the effects of clouds on the inner edge boundaries.

Speaker: Ramses Ramirez, Cornell Univ.