Astronomers are keeping a wary eye on a large asteroid expected to narrowly miss hitting Earth next Friday in the closest known approach of a dangerous cosmic object since NASA started tracking such debris.

National Aeronautics and Space Administration experts who plotted its trajectory are confident that the primordial rock, weighing an estimated 130,000 metric tons, will pass within "a remarkably close distance" of Earth, nearer than many orbiting communications satellites but far enough away to safely speed past...