The Distribution of Debris Disks around Solar-Type Stars
Mike Werner, JPL
Using the MIPS
camera on the Spitzer Space Telescope, we have searched for infrared
excesses around 58 FGK main-sequence field stars. With a median
age of ~5 Gyr, the stars are older than those which typically have
excess emission due to a debris disk. Nevertheless, we have detected 70
micron excesses around 6 stars at the 3-sigma confidence level.
This extra emission is produced by cool material (<100 K) located
beyond 10 AU, well outside the ''habitable zones'' of these systems and
consistent with the presence of Kuiper Belt analogues with ~100 times
more emitting surface area than in our own planetary system. Only
one star, HD69830, shows excess emission at 24 microns, corresponding
to dust with temperatures > 300 K located inside of 1 AU.
While debris disks with L_disk/L_* > 10^-3 are rare around old FGK
stars, we find that the disk frequency increases from 2+-2% for disks
with L_disk/L_* > 10^-4 to 11+-5% for L_d/L_* > 10^-5. Fits
of this distribution suggest that the amount of dust in our Solar
System is not largely below the average for similar field stars.