During 2008 OS7's approach to Earth on February 2, NASA's Deep Space Network Planetary Radar collected the first detailed images of the stadium-sized asteroid. On February 2, a large asteroid drifted safely past Earth at a distance of about 1.8 million miles (2.9 million kilometers, or 7.5 times the distance between Earth and the Moon).
While the asteroid, named 2008 OS7, is not in danger of impacting Earth, scientists at NASA's Jet Propulsion Laboratory in Southern California used a powerful radio antenna to better determine the size, rotation, shape and surface details of the near-Earth object (NEO). Prior to this close approach, the 2008 OS7 asteroid was too far from Earth for planetary radar systems to image it.
The asteroid was discovered on July 30, 2008, during a routine search for near-Earth objects by the NASA-funded Catalina Sky Survey, which is headquartered at the University of Arizona in Tucson. After its discovery, observations of the amount of light reflected from the asteroid's surface revealed that it was approximately 650 to 1,640 feet (200 to 500 meters) wide and rotating relatively slowly, rotating once every 29 and a half hours.
Petr Pravec of the Institute of Astronomy of the Czech Academy of Sciences in Ondrejov, Czech Republic, determined the orbital period of 2008 OS7. He observed the asteroid's light curve, which is the change in the brightness of a celestial body over time. As the asteroid rotates, changes in its shape change the brightness of the reflected light that astronomers see, and recording these changes can provide insights into the asteroid's rotation period.
During the close approach on February 2, JPL's radar team imaged the asteroid using the 230-foot (70-meter) Goldstone Solar System Radar dish at the Deep Space Network Facility near Barstow, California. Scientists found that the asteroid's surface has both circular and angular areas, as well as a small concave surface. They also found that the asteroid was smaller than previously estimated -- about 500 to 650 feet (150 to 200 meters) across -- and confirmed its unusually slow spin rate.
Potentially dangerous but safe for now
The epigraphic radar observations also provided key measurements of the asteroid's distance from Earth as it passed. These measurements can help scientists at NASA's Center for Near-Earth Object Studies (CNEOS) refine calculations of asteroids' orbital paths around the sun. Asteroid 2008OS7 orbits the sun every 2.6 years, traveling from within the orbit of Venus to passing through the orbit of Mars at its farthest point.
CNEOS, managed by JPL, calculates the orbits of every known near-Earth object to provide an assessment of potential impact hazards. 2008 OS7 is classified as a potentially hazardous asteroid due to the closeness of its orbit to Earth's and its size, but its February 2 approach was the closest it has been to our planet in at least 200 years.
While NASA reports on near-Earth objects of all sizes, the agency is tasked by Congress with detecting and tracking objects 460 feet (140 meters) or larger, which could cause significant damage to the ground if they hit our planet.
The Goldstone Solar System Radar Group and CNEOS are supported by the Near-Earth Object Observations Program of the Planetary Defense Coordination Office at NASA Headquarters in Washington. The Deep Space Network has program oversight by the Space Communications and Navigation (SCaN) Program Office within the Space Operations Mission Directorate, also located at NASA Headquarters.
Compiled source: ScitechDaily