The manager called in the chief Excalibur scientist, who analyzed the data and decided the new object was a long period comet.

After this, the only unknown objects will be long period comets that will remain unseen until a few months before impact.

This would give the comet a period of 1430 30 years and so making it the longest period comet to be seen on two separate returns.

For long period comets, most of the time it will be so far from the Sun that it will be too cold for evaporation of ices to occur.

Comets are distinguished by their orbits; long period comets have long elliptical orbits, randomly inclined to the plane of our solar system, and with periods greater than 200 years.