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A Question About Comet Orbits

-- zev | October 23, 2019

Question:

I understand that Haley’s comet comes about every 70 years and visits earth twice in about 6 months. Can there be a comet that has a much longer
orbit and would visit earth twice in 45 years? Thank you.

-- zev

Answer:

Comets have orbits which are highly elliptical, with their closest approach (perihelion) lasting only a few months. I don’t see how it could be possible for a comet to have an orbit that allowed it to pass near the orbit of the Earth on timescales of years, as this would require an orbit perihelion that is unphysically large.

-- Jeff Mangum

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