What is the solar systems vacuum cleaner?

Answer 1

I presume this refers to the way that small, meteoroid-sized objects are swept from the solar system. Any object in orbit around the sun is "flying" through the light emitted by the sun, and because of orbiting object's motion, the light shines slightly stronger its front side. This is called "stellar aberration", and affects the apparent position of stars as seen from the earth.

The effect is small, because orbital speeds are thousands of times slower than the speed of light, but it never ends. Light produces a small pressure on anything it shines on, and this pressure, slightly stronger on the front side of solar system planetoids, causes these objects to lose orbital energy and spiral toward the sun. Objects weighing a ton or more are too massive to be affected in this way, but objects weighing a gram or less take only a few million years to fall into the sun.

Since the solar system is much older than that, this cleans inter-planetary space of small grains; otherwise we'd see many more meteors than we do.