W. von Bloh^a, M. Cuntz^b, S. Franck^a, and C. Bounama^a

Astrobiology 3(4), 681-688 (2003)

^aPotsdam Institute for Climat e Impact Research (PIK), Telegrafenberg, P.O. Box 60 12 03, 14412 Potsdam, Germany.

^bDepartment of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019, USA.

Abstract

We discuss the possibility of Earth-type planets in the planetary system of 55 Cancri, a nearby G8 V star, which is host to two, possibly three, giant planets. We argue that Earth-type planets around 55 Cancri are in principle possible. Several conditions are necessary. First, Earth-type planets must have formed despite the existence of the close-in giant planet(s). In addition, they must be orbitally stable in the region of habitability considering that the stellar habitable zone is relatively close to the star compared to the Sun because of 55 Cancri's low luminosity and may therefore be affected by the close-in giant planet(s). We estimate the likelihood of Earth-type planets around 55 Cancri based on the integrated system approach previously considered, which provides a way of assessing the long-term possibility of photosynthetic biomass production under geodynamic conditions.

Figure: The habitable zone around 55 Cnc assuming a luminosity of L = 0.61 L_s. The colored areas indicate the extent of the HZ for different relative continental areas. The lower limit, mean value, and upper limit of the assumed star/planet age are 3.5, 4.5, and 5.5 Gyr, indicated by the y-axis and the dashed and dotted line, respectively. The orbital stability limit lies between 0.69 AU and 0.75 AU, depending on masses and orbital parameters of the giant planets (see text). No relevant stability limit exists if the middle giant planet is absent.