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Elliptical galaxies have dynamically hot ($\sigma_{1D}$ ~ 100 -- 300 kms$^{-1}$) populations of stars, and presumably, smaller objects like comets.Because interstellar minor bodies are moving much faster, they hit planetsharder and more often than in the local Galaxy. I estimate the rates forChicxulub-scale impacts on an Earth-size planet in elliptical galaxies as apotential habitability constraint on intelligent life. Around most stars in anormal elliptical galaxy, these planets receive only ~0.01 -- 0.1 Gyr$^{-1}$,although hazardous rates may be common in certain compact early-type galaxiesand red nuggets. About 5% of the stellar mass is in a region where the rate is>10 Gyr$^{-1}$, large enough to dominate the mass extinction rate. Thissuggests that elliptical galaxies have an exclusion zone of order one hundredparsecs in radius around their centers for the evolution of intelligent life.

Life in Elliptical Galaxies: Hot Spheroids, Fast Stars, Deadly Comets?