LOS ANGELES, Aug. 30 (Xinhua) -- Asteroid Florence, a large near-Earth asteroid, will safely pass by Earth on Friday, at a distance of about 7 million kilometers, or about 18 Earth-Moon distances, according to the U.S. National Aeronautics and Space Administration (NASA).

Officially designated 3122 Florence, the natural remnant of the formation of the solar system is the largest asteroid to pass so close by since NASA started tracking near-Earth asteroids. Measurements from NASA's Spitzer Space Telescope and NEOWISE mission indicate it's about 4.4 kilometers across.

"While many known asteroids have passed by closer to Earth than Florence will on September 1, all of those were estimated to be smaller," Paul Chodas, manager of NASA's Center for Near-Earth Object Studies (CNEOS) at the agency's Jet Propulsion Laboratory (JPL), said in statement.

The 2017 encounter will be Florence's closest pass since 1890 and until at least 2500. It provides an opportunity for scientists to study this asteroid up close. Asteroid Florence is expected to be an excellent target for ground-based radar observations, NASA said.

Florence was discovered by Schelte "Bobby" Bus at Siding Spring Observatory in Australia in March 1981. It is named in honor of Florence Nightingale (1820-1910), the founder of modern nursing.