The largest asteroid in more than a century will whiz safely past Earth on September 1 at a safe but unusually close distance of about 4.4 million miles (7 million kilometers), NASA said. The asteroid was discovered in 1981, and is named Florence after the famed 19th century founder of modern nursing, Florence Nightingale. "Florence is the largest asteroid to pass this close to our planet since the first near-Earth asteroid was discovered over a century ago," said a US space agency statement.