Probe launched by the doomed people of Kataan, which caused Picard to live an entire lifetime on their world in the space of minutes in The Inner Light.
The Kataan probe was a small rocket launched a thousand years before the 24th century by the people of Kataan, whose sun was dying. They knew their world could not be saved and built the probe to carry the memory of their civilisation to whoever found it.
In The Inner Light, the Enterprise-D found the probe drifting near the Parvenium system. It scanned the ship and struck Picard with a beam that left him unconscious, and in his mind he woke as Kamin, an iron weaver in the village of Ressik. Over decades he raised a family, learned to play the flute and studied the drought that signalled the planet's end.
Only about twenty-five minutes passed on the Enterprise. When Picard awoke, the crew recovered a flute from inside the probe, the same one Kamin had played, and he kept it as a link to the life he had lived.