Tuesday, September 12, 2017

Giant Asteroid to Swoosh by Earth on September 1

Giant Asteroid to Swoosh by Earth on September 1:



Image credit: NASA/JPL-Caltech




A massive asteroid over four kilometers wide is expected to fly by our planet on Friday, September 1. The space rock, designated 1981 ET3 (also known as Florence), will miss the Earth at a safe distance of 18.5 lunar distances (LD), or seven million kilometers.

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

Measurements made by NASA's Spitzer Space Telescope and NEOWISE mission indicate that Florence is about 4.4 kilometers in size, what makes it one of the largest known near-Earth asteroids. It is also the largest object to pass by our planet this close since NASA’s program to detect and track near-Earth asteroids began.

“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 has an absolute magnitude of 14.1 and a rotation period of approximately 2.36 hours. The asteroid has a semimajor axis of about 1.77 AU and orbits the sun every 2.35 years.

The close approach of Florence on September 1 will take place at 12:06 UTC, when it will pass by our planet with a relative velocity of 13.53 km/s. The upcoming fly-by will offer an excellent opportunity to conduct radar observations of this object. 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. These images could show the real size of Florence and could also reveal surface details as small as about 10 meters.

Florence is classified as one of the 1,803 Potentially Hazardous Asteroids (PHAs) currently known. PHAs are asteroids larger than 100 meters that can come closer to Earth than 19.5 LD. None of the known PHAs is on a collision course with our planet.

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