Objects with highly eccentric orbits are both very uncommon and very unlikely to intercept Earth. The period in which they have near misses is on the order of

Objects with highly eccentric orbits are both very uncommon and very unlikely to intercept Earth. The period in which they have near misses is on the order of thousands of years at least. Even if we could see them from their high altitude we don't have enough information to predict where they'll be on the next intercept. My understanding is that this kind of threat is usually lumped in with comets, whereas threat asteroids are lumped in with low eccentricity big rocks.