  Spitzer Space Telescope photometry and spectroscopy of BD +20 307 show that
all of the dust around this remarkable Gyr-old spectroscopic binary arises
within 1 AU. No additional cold dust is needed to fit the infrared excess.
Peaks in the 10 and 20 micron spectrum are well fit with small silicates that
should be removed on a timescale of years from the system. This is the dustiest
star known for its age, which is >1 Gyr. The dust cannot arise from a
steady-state collisional cascade. A catastrophic collision of two rocky,
planetary-scale bodies in the terrestrial zone is the most likely source for
this warm dust because it does not require a reservoir of planetesimals in the
outer system.
