The scientists at NASA’s Jet Propulsion Laboratory in Southern California recently tracked two asteroids 2024 MK and 2011 UL21 who safely passed Earth. Of this, it was observed that one turned out to have a little moon orbiting it.
According to NASA, on June 27, the asteroid 2011 UL21 passed Earth at a distance of 4.1 million miles (6.6 million km), or almost 17 times that of the Moon. UL21 was found in 2011 in Tucson, Arizona, by the NASA-funded Catalina Sky Survey.
NASA announced that JPL scientists, using the 230-foot-wide (70-meter) Goldstone Solar System Radar, named Deep Space Station 14 (DSS-14), near Barstow, California, found that the asteroid is approximately spherical and forms a binary system with a smaller asteroid, or moonlet, orbiting it at a distance of around 1.9 miles.
Speaking on this, Lance Benner, principal scientist at JPL who helped lead the observations said, “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,” as quoted by JPL's blog post.
Speaking about the other observed asteroid 2024 MK that was discovered only 13 days before, made its relatively rare closest approach to Earth.
NASA's JPL in a blog post also revealed that, on June 29, the same group of scientists observed asteroid 2024 MK passing close to Earth from a distance of only 184,000 miles (295,000 kilometers), which is slightly more than three-quarters of the distance between the Moon and Earth.
“This was an extraordinary opportunity to investigate the physical properties and obtain detailed images of a near-Earth asteroid,” Benner said. Just 13 days back, i.e. on June 16, the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) at the Sutherland Observation Station in South Africa made the initial identification of asteroid 2024 MK.
