Rum, a diamond-shaped island off the western coast of Scotland, is home to 40 people. Most of the island — 40 square miles of mountains, peatland and heath — is a national nature reserve, with residents mainly nestled around Kinloch Bay to the east. What the Isle of Rum lacks is artificial illumination. There are no streetlights, light-flooded sports fields, neon signs, industrial sites or anything else casting a glow against the night sky. On a cold January day, the sun sets early and rises late, yielding to a blackness that envelopes the island, a blackness so deep that the light of stars manifests suddenly at dusk and the glow of the moon is bright enough to navigate by.

For this reason, Rum was recently named Europe’s newest dark-sky sanctuary, a status that DarkSky International, a nonprofit organization focused on reducing light pollution, has granted to only 22 other places in the world. With the ever-increasing use of artificial lighting at night, places where people can gaze at the deep, ancient light of the universe are increasingly rare. Rum’s designation is the result of a long, meticulous bid by the Isle of Rum Community Trust. The effort was led by Alex Mumford, the island’s former tourism manager, and Lesley Watt, Rum’s reserve officer, with the support of Steven Gray and James Green, two astronomers who started Cosmos Planetarium, a mobile theater offering immersive virtual tours of the night sky. Rum “stands for something greater,” Mr. Mumford said, and aspires to be “a haven for others to experience the darkness and the Milky Way.”