Astronomers finally got a closer look at a stadium-sized asteroid that was first spotted 16 years ago. The flying object approached Earth in what was a planetary flyby.
The space rock, named 2008 OS7, passed by Earth on February 2 while NASA’s Deep Space Network planetary radar maintained surveillance. The asteroid came within 2.9 million kilometers of Earth, which is almost 7.5 times the distance between the Earth and the Moon.
While the asteroid posed no risk to the planet, scientists used a powerful radio antenna to better determine the size, rotation, shape and surface details of this near-Earth object.
“Until this approach, asteroid 2008 OS7 had been too far from Earth for planetary radar systems to image it,” NASA said in an update.
The asteroid was first detected on July 30, 2008, during routine search operations for near-Earth objects in the surrounding area. A team from the University of Arizona in Tucson was scanning the open space.
Observations at the time revealed that it was approximately 200 to 500 meters wide and rotated comparatively slowly, completing one rotation every 29.5 hours.
Astronomers looked at the asteroid’s light curve (or how the object’s brightness changes over time) to estimate its rotation. NASA said that as the asteroid rotates, variations in its shape change the brightness of the reflected light that astronomers see, and those changes are recorded to understand the asteroid’s rotation period.
What happened on February 2?
During the asteroid’s close approach on February 2, astronomers used the giant Goldstone Solar System Radar dish at the Deep Space Network facility to image the asteroid and better understand this flying neighbor.
Astronomers discovered that the asteroid’s surface has a mix of rounded and more angular regions with a small concavity. They also discovered that the asteroid is smaller than previously estimated (between 150 and 200 meters wide) and confirmed its unusually slow rotation.
“The observations also provided key measurements of the asteroid’s distance from Earth as it passed. Asteroid 2008 OS7 orbits the Sun once every 2.6 years, traveling from within the orbit of Venus and passing through the orbit of Mars at its farthest point,” NASA said. .
Due to the proximity of its orbit to Earth’s and its size, 2008 OS7 is classified as a potentially hazardous asteroid.