Dynamical considerations, presented herein via analytic scalings and numerical experiments, imply that Earth-mass planets accreting in regions that become habitable zones of M dwarf stars form within several million years. Temperatures in these regions during planetary accretion are higher than those encountered by the material that formed the Earth. Collision velocities during and after the prime accretionary epoch are larger than for Earth. These factors suggest that planets orbiting low-mass main-sequence stars are likely to either be too distant (and thus too cold) for carbon/water based life on their surfaces or have abundances of the required volatiles that are substantially less than on Earth.
The Astrophysical Journal
- Pub Date:
- May 2007
- Stars: Planetary Systems: Formation;
- Planets and Satellites: Formation;
- 11 pages, 1 figure, Astrophysical Journal Letters, in press