What is Comet Swift–Tuttle’s approximate minimum orbit intersection distance from Earth?

Comet Swift–Tuttle’s approximate minimum orbit intersection distance from Earth is 0.0009 astronomical units. The minimum orbit intersection distance, or MOID, compares the closest possible geometric separation between two orbital paths.

A MOID is not a prediction that two bodies will occupy the same point at the same time. Actual encounter risk also depends on orbital timing, gravitational perturbations, and how accurately the orbit is known. Swift–Tuttle’s small Earth MOID is one reason astronomers monitor its long-term orbit.

The figure is also different from the comet’s actual closest approach during a particular return. The Perseid meteor shower is produced by dust crossing Earth’s path, while the much larger comet itself remains on its own orbit around the Sun.