How (Some) Comets Survive Solar Death Dive
The Oort Cloud is believed to be composed of billions, possibly trillions of icy planetesimals which ultimately, become cometary nuclei if dislodged from their orbit and sent in toward the inner solar system.
So what strange force could possibly eject comets from their deep freeze in the Oort Cloud?
One of the most popular theories is that the gravity from the Milky Way itself is responsible for sending comets in our direction. Just as the moon exerts a pull on the Earth, making its oceans (and to a lesser degree the land) bulge toward the moon, so the pull of gravity from our galaxy is thought to make the Oort Cloud bulge, dislodging the comets.
Another possible cause for ejecting comets is the gravitational effect from stars that pass close to our system as they orbit around the Milky Way.
Unfortunately, no man-made spacecraft has reached the distance of the Oort Cloud and space observatories aren't powerful enough to prove its existence, so for now, it will remain a topic for debate. One thing is for certain though, long period comets will continue to unexpectedly appear out of the depths of space, like a whale from the depths of the oceans. Quite where they come from though will remain a mystery.