Space] The huge asteroid that cruised past Earth last week in a record-breaking flyby has two moons, radar images reveal.
On Sept. 1, the 2.8-mile-wide (4.5 kilometers) near-Earth asteroid 3122 Florence
zoomed within 4.4 million miles (7 million km) of our planet — a mere
18 times the distance from Earth to the moon. No other space rock that
big has come so close since NASA began tracking asteroids in earnest,
agency officials have said.
The flyby therefore presented a rare scientific opportunity, and
astronomers around the world trained a number of instruments on Florence
as it approached. One such facility was NASA's Goldstone Deep Space
Communications Complex in California, which captured some dramatic and
informative views. [Famous Asteroid Rock Flybys and Close Calls (Infographic)]
For example, imagery obtained by the 230-foot (70 m) dish at Goldstone
confirmed Florence's size and its 2.4-hour rotation period, values that
scientists had already figured out thanks to previous observations. And
Goldstone revealed that the asteroid is roughly spherical, with an equatorial ridge and at least one big crater, NASA researchers said.
Florence's shape was a mystery before last week's flyby. Also unknown
was whether the space rock had any moons, but Goldstone's imagery
"The sizes of the two moons are not yet well-known, but they are
probably between 100-300 meters (300-1,000 feet) across," researchers
Lance Benner, Shantanu Naidu, Marina Brozovic and Paul Chodas, of the
Center for NEO (Near-Earth Object) Studies at NASA's Jet Propulsion
Laboratory in Pasadena, California, wrote in a Sept. 1 update.
"The times required for each moon to revolve around Florence are also
not yet known precisely, but appear to be roughly 8 hours for the inner
moon and 22 to 27 hours for the outer moon," the researchers added. "The
inner moon of the Florence system has the shortest orbital period of
any of the moons of the 60 near-Earth asteroids known to have moons. In
the Goldstone radar images, which have a resolution of 75 m [250 feet],
the moons are only a few pixels in extent and do not reveal any detail." Read More