Scientists recently monitored two space rocks zipping by Earth. One surprised them with a tiny moon in tow! NASA keeps a watchful eye on asteroids, constantly tracking their paths to avoid any future collisions. These recent flybys posed no danger, but they offered valuable clues for future preparedness.
Asteroids are leftover debris from our solar system's birth, and studying them is like peering back in time. Their size, orbit, and makeup can reveal secrets about our cosmic neighbourhood.
To track and image these space rocks, NASA's Jet Propulsion Laboratory in California used a powerful tool called planetary radar. This system, part of the Deep Space Network, acts like a giant cosmic radar, sending radio waves that bounce off the asteroids and return, creating detailed images.
On June 27th, asteroid 2011 UL21 made its closest recorded approach to Earth, passing by at a safe distance of 17 times the Earth-Moon distance (4.1 million miles or 6.6 million kilometres). This nearly mile-wide (1.5 kilometre-wide) asteroid was first discovered in 2011 and has been classified as potentially hazardous due to a small chance of a future impact. However, astronomers have calculated its future trajectory and determined it poses no imminent threat.
Interestingly, recent radar observations from the Goldstone Solar System Radar in California revealed a surprising feature: 2011 UL21 is not alone! It has a small moonlet orbiting it at a distance of about 1.9 miles (3 kilometres).
"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 led the observations, in a statement.
NASA's exploration of asteroids, like the upcoming Lucy mission to Trojan asteroids, sheds light on how common moonlets are in our solar system. The DART mission even tested deflecting an asteroid by crashing into its moonlet, Dimorphos!
Spotting close-approaching asteroids can be tricky. Recently discovered asteroid 2024 MK zoomed by Earth at a mere 184,000 miles (295,000 kilometres) just 13 days after detection! This close shave emphasizes the need for improved near-Earth asteroid tracking.
ATLAS, a telescope system in South Africa, first spotted 2024 MK. Though potentially hazardous, its path doesn't pose an immediate threat to Earth.
Radar observations revealed a fascinating 500-foot (150-meter) wide asteroid with a rough, elongated shape. It even boasts 30-foot (10-meter) boulders and interesting surface features.
Earth's gravity nudged the asteroid slightly, shaving 24 days off its 3.3-year orbit around the sun. This close encounter highlights the importance of studying these relatively rare near-Earth objects.
"This was an extraordinary opportunity to investigate the physical properties and obtain detailed images of a near-Earth asteroid," Benner said.
