Why Comet C/2020 F3 Neowise returns even it's orbit is near- parabolic?

Astronomy Asked by Athul R T on August 19, 2020

I have read in Wikipedia about Comet C/2020 F3 Neowise that it’s orbit is near-parabolic. But in another section, it says that it is a non-periodic comet whlith orbital period ranging from 4500 years to 6800 years.

My doubt is how a comet returns back if it is in a parabolic orbit and why it is non-periodic?

Here is the Wikipedia link:

2 Answers

Supplementary answer:

"Near-parabolic" means almost or nearly parabolic, but not quite. Another term would be "highly elliptical". Technically speaking, no realistic orbit can really be exactly parabolic since that means eccentricity is exactly 1.00000000000.... and most of Physics (solar photon pressure, relativity, gravitational perturbations from other bodies, etc.) doesn't happen.

You can complain that in your linked Wikipedia article:

C/2020 F3 (NEOWISE) or Comet NEOWISE is a retrograde comet with a near-parabolic orbit discovered on March 27, 2020, by astronomers using the NEOWISE space telescope.

the term "near-parabolic" hyperlinks to Parabolic trajectory. Probably the "near" part should not be part of the link.

Correct answer by uhoh on August 19, 2020

Comet naming conventions limit "periodic comets" to those comets whose orbital period is less than 200 years. Comets in elliptical orbits with a period of greater than 200 years are classified as non-periodic. Comets in parabolic or hyperbolic trajectories are also classified as non-periodic (and they will never again approach the primary).

Answered by David Hammen on August 19, 2020

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