There are tiny comets orbiting foreign suns. And human beings can detect them.
Six times, about 800 years ago, dark things passed between the bright-yellow dwarf star KIC 3542116 and Earth. They were small in cosmic terms, about 330 billion tons (300 billion metric tons). That’s about the size of Halley’s Comet, or just one-245 millionth the mass of Earth’s moon.
But they were big enough. They blocked a fraction of a fraction of the light that was streaming outward from that star. Eight hundred years later, the sensitive lens of the Kepler Space Telescope — a nearly meterwide piece of precision-cut glass floating in the darkness of space — detected that dimming as KIC 3542116’s ancient light reached this solar system.