Near-Earth asteroid, computer artwork.
NASA has released spectacular new images of one of the largest asteroids to pass close to Earth in recent years—and revealed a moon in its orbit.
On June 27, asteroid 2011 UL21 (also known as 415029) flew by Earth within 4.1 million miles (6.6 million kilometers), about 17 times the distance to the moon.
This asteroid was revealed to be a mile-wide (about 1.5 kilometers) in diameter, a little smaller than suspected before its arrival. It was discovered in 2011 by the NASA-funded Catalina Sky Survey in Tucson, Arizona.
These seven radar observations by the Deep Space Network’s Goldstone Solar System Radar shows the ... [+]
No Threat
Calculations of its future orbits show that it won’t pose a threat to our planet for the foreseeable future, according to NASA's Jet Propulsion Laboratory in Southern California.
The stunning images were made possible by the 230-foot-wide (70-meter) Goldstone Solar System Radar antenna near Barstow, California, a crucial part of NASA's Deep Space Network. Scientists used this antenna to send radio waves to the asteroid and received the reflected signals, revealing the asteroid’s spherical shape and its “moonlet” companion.
Binary System
“It is thought that about two-thirds of asteroids of this size are binary systems, and their discovery is particularly important because we can use measurements of their relative positions to estimate their mutual orbits, masses, and densities, which provide key information about how they may have formed,” said Lance Benner, principal scientist at JPL, who was involved in the observations.
2011 UL21’s close pass was among the top 10 largest asteroids to have passed within 4.6 million miles (7.5 million kilometers) from the Earth in the last 124 years, according to the Center for Near Earth Object Studies at NASA’s Jet Propulsion Laboratory.
The Goldstone Solar System Radar, part of NASA’s Deep Space Network, made these observations of the ... [+]
Second Asteroid
During the same observations, NASA also snapped another asteroid, 2024 MK, which was only discovered on June 16. It passed a mere 184,000 miles (295,000 kilometers from Earth—just 75% of the distance between Earth and the moon—though at 500 feet (150 meters) wide, this asteroid was far smaller.
The radar images of 2024 MK revealed a detailed image (above) of the asteroid’s surface, including concavities, ridges and boulders about 30 feet (10 meters) wide.
Such close approaches of near-Earth objects the size of 2024 MK occur only once every couple of decades. “This was an extraordinary opportunity to investigate the physical properties and obtain detailed images of a near-Earth asteroid,” said Benner.
Wishing you clear skies and wide eyes.
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