A small asteroid designated 2016 RB1 safely flew past Earth on Sept. 7 at 10:20 a.m. PDT (1:20 p.m. EDT / 17:20 UTC) at a distance of about 25,000 miles (40,000 kilometers, or just less than 1/10th the distance of Earth to the moon). Because the asteroid’s orbit carried it below (or over) Earth’s south pole, it did not pass within the orbits of communication or weather satellites. 2016 RB1 is estimated to be between 25 to 50 feet (7 and 16 meters) in diameter. It is the closest the space rock will come to Earth for at least the next half century.
Asteroid 2016 RB1 was discovered on Sept. 5, 2016, by astronomers using the 60-inch Cassegrain reflector telescope of the Catalina Sky Survey, located at the summit of Mount Lemmon in the Catalina Mountains north of Tucson, Arizona -- a project of NASA'S NEO Observations Program in collaboration with the University of Arizona.
The bus-sized space rock is travelling at 18,119 miles per hour (29,160 km/h). The asteroid’s speed and nearness to our planet means that some lucky observers might have seen the asteroid’s movement in front of the stars. That observation required a telescope, as it was too dim to see with the unaided eye.
Although the flyby of the space rock favors Southern Hemisphere observers during closest approach, some observatories from different locations have been able to capture the speeding asteroid.
It is the third asteroid that comes closer than the moon’s distance during the first week of September, 2016. The other asteroids were 2016 RR1, which passed at 0.32 lunar distances on September 2, while hours later, asteroid 2016 RS1 flyby occurred at 0.48 times the Earth-moon distance.
The Center for NEO Studies website has a complete list of recent and upcoming close approaches, as well as all other data on the orbits of known NEOs (near-Earth objects), so scientists and members of the media and public can track information on known objects.