[adorno]

Scientists have only spotted a handful of comets active so far from the sun, where temperatures are still too cold for, say, water ice to turn to vapor, a typical type of cometary activity.

That's because it's not a comet.

It's an inter-galactic vessel, with an exhaust system which emulates water vapor tails of comets.

[BenLurkin]

The tail would have to be towards the sun if they wanted to decelerate.