Prof. Eric Gaidos
University of Hawaii
Dying Stars and Living Worlds: Short-Lived Radionuclides and the
Abundance of Planetary Water
Monday, December 10, 2007, 4:00 p.m.
Location: Thornton Hall 411
Refreshments at 3:45 p.m.
ABSTRACT
Searches for extrasolar planets are now extending into the regime of
objects not much more massive than the Earth, and the expectation that
many such planets will be detected by new missions and instruments
raises the obvious question of how many of them will be Earth-like. An
important event in our Solar System's early history was the injection of
short-lived radionuclides, probably from one or more nearby massive
stars. One of these, aluminum-26, was a significant source of internal
heat in planetesimals and growing protoplanets; indeed, there is
compelling evidence for melting and differentiation of some meteorite
parent bodies within the first million years of Solar System history.
Heat from the decay of short-lived radionuclides would have driven
hydrothermal circulation and alteration in such bodies and others have
proposed that the boundary between "dry" and "wet" material in the
present Solar System was set by the time-scale of accretion vs. the
half-life of Al-26
(720 kyr). However, studies of the star formation process and the
time-scale of dissipation of planet-forming disks suggests that initial
inventories of short-lived radionuclides vary between disks by orders of
magnitude, and that the majority of systems would have received much
less Al-26 from their birth environment. This has consequences for the
abundance of planetary water in these systems and their propensity to
host Earth-like planets.