Asteroid Florence, nearly 2.7 miles wide (4.4 kilometers) will pass safely by Earth on Sept. 1, 2017, at a distance of about 4.4 million miles (7.0 million kilometers, or about 18 Earth-Moon distances). Florence is among the largest near-Earth asteroids that are several miles in size; measurements from NASA’s Spitzer Space Telescope and NEOWISE mission indicate it’s about 2.7 miles (4.4 kilometers) in size.
Asteroid 3122 Florence, in honor of Florence Nightingale (1820-1910), the founder of modern nursing, is among the largest near-Earth asteroids that are several miles in size to sail near Earth since the NASA first started tracking such phenomena in 1990.
An object the size of Florence would have a global impact if it struck the Earth, though, this isn’t expected to happen. The 2017 encounter is the closest by this asteroid since 1890 and the closest it will ever be until after 2500.
“While many known asteroids have passed by closer to Earth than Florence will on September 1, all of those were estimated to be smaller,” said Paul Chodas, manager of NASA’s Center for Near-Earth Object Studies (CNEOS) earlier this month from Pasadena, California. “Florence is the largest asteroid to pass by our planet this close since the NASA program to detect and track near-Earth asteroids began.”
This relatively close encounter provides an opportunity for scientists to study this asteroid up close. Florence is expected to be an excellent target for ground-based radar observations. The resulting radar images will show the real size of Florence and also could reveal surface details as small as about 30 feet (10 meters). Deep space radar is a powerful technique for studying its size, shape, rotation, surface features and roughness, and for more precise determination of their orbital path.
Asteroid Florence was discovered by Schelte “Bobby” Bus in Australia in March 1981.
Florence will brighten to ninth magnitude in late August and early September, when it will be visible in small telescopes for several nights as it moves through the constellations Piscis Austrinus, Capricornus, Aquarius, and Delphinus.