# Galactic tide and orbital evolution of comets

## TL;DR

This study numerically solves the equations of motion for Oort cloud comets, incorporating realistic galactic gravitational effects, revealing significant differences from simpler models and implications for comet return rates and historical extinction events.

## Contribution

It introduces physically improved galactic tide models for comet orbital evolution, showing they produce notably different results from conventional models.

## Key findings

- Number of comet returns is about twice as high with improved models.
- Realistic models significantly differ from conventional galactic tide models.
- Potential link between Oort cloud comets and the dinosaurs extinction event.

## Abstract

Equation of motion for a comet in the Oort cloud is numerically solved. Orbital evolution of the comet under the action of the gravity of the Sun and the Galaxy is presented for various initial conditions. Oscillations of the Sun with respect to the galactic equatorial plane are taken into account. Real values of physical quantities concerning the gravitational action of the galactic neighbourhood of the Sun are important. The results are compared with currently used more simple models of the galactic tide. It turns out that physically improved models yield results which significantly differ from the results obtained on the basis of the conventional models. E.g., the number of returns of the comets into the inner part of the Solar System are about two times greater than it is in the conventional models. It seems that a comet from the Oort cloud can be a source of the dinosaurs extinction at about 65 Myr ago. A close encounter of a star or an interstellar cloud disturbed a comet of the Oort cloud in the way that its semi-major axis increased/decreased above the value 5 $\times$ 10$^{4}$ AU and the comet hit the Earth.