Collision with interstellar matter

In 1996 it was estimated that the movement of the solar system through the galactic environment would lead to a collision with a cloud of interstellar matter in some 50,000 years time. The cloud is up to a million times more dense than the current surroundings of the solar system. The encounter could sharply alter the Earth's atmosphere and climate. Another cloud may be as near as 20,000 light years away.