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Joint Astrophysics Colloquium
Norm Murray CITA The recent discovery of Jupiter-mass objects orbiting nearby solar-type stars raises the question, are there Earth-like bodies orbiting nearby stars? Since the doppler technique currently used to search for planets is not sensitve to such low mass objects, other methods are called for. One alternative is to look for the signature of accreted asteroids in the stellar spectrum; it is believed that our sun has accreted about two Earth masses of rocky material. In this talk I will describe the results of such a search. I find that the metallicity [Fe/H] of main sequence stars, when plotted as a function of stellar mass, mimics the pattern seen in lithium abundances in open clusters. Using Monte Carlo models I find that, on average, these stars have accreted ~0.4 Earth masses of iron while on the main sequence. A much smaller sample of 19 stars in the Hertzsprung gap, which are slightly evolved and whose convection zones are significantly more massive, have lower average [Fe/H], and their metallicity shows no clear variation with stellar mass. These findings suggest that terrestrial-type material is common around solar type stars.
Thursday, February 1st 2001, 12:30 |