Large Asteroid to Safely Pass Earth on Sept. 1

Asteroid Florence, a large near-Earth asteroid, 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.

“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) at the agency’s Jet
Propulsion Laboratory in 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. Radar imaging is planned at NASA’s Goldstone
Solar System Radar in California and at the National Science
Foundation’s Arecibo Observatory in Puerto Rico. 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).

Asteroid 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. The 2017 encounter is the closest by this
asteroid since 1890 and the closest it will ever be until after
2500. 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

Radar has been used to observe hundreds of asteroids. When
these small, natural remnants of the formation of the solar
system pass relatively close to Earth, deep space radar is a
powerful technique for studying their sizes, shapes, rotation,
surface features and roughness, and for more precise
determination of their orbital path.

JPL manages and operates NASA’s Deep Space Network, including
the Goldstone Solar System Radar, and hosts the Center for
Near-Earth Object Studies for NASA’s Near-Earth Object
Observations Program, an element of the Planetary Defense
Coordination Office within the agency’s Science Mission

More information about asteroids and near-Earth objects can be
found at:

For more information about NASA’s Planetary Defense
Coordination Office, visit:

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News Media Contact

DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.

Laurie Cantillo / Dwayne Brown
NASA Headquarters, Washington
202-358-1077 / 202-358-1726 /