A large asteroid with a moon, captured passing close to Earth

3 Jul. () –

NASA’s Jet Propulsion Laboratory (JPL) has made radar observations of two asteroids that passed close to our planet in late June. with only hours of interval.

One turned out to have a small moon orbiting it, while the other had been discovered just 13 days before its closest approach to Earth. There was no risk of either near-Earth object hitting our planet, but the observations will provide valuable practice for planetary defense, as well as information about their sizes, orbits, rotation, surface details, and clues about their composition and formation. JPL reported.

Asteroid 2011 UL21 passed close to Earth on June 27 at a distance of 6.6 million kilometers, or about 17 times the distance between the Moon and Earth, and was discovered in 2011 by the Catalina Sky Survey. But this is the first time it has come close enough to Earth to be imaged by radar. Although the nearly 1.5-kilometer-wide object is classified as potentially hazardous, calculations of its future orbits show that will not pose a threat to our planet in the foreseeable future.

A MOON 3 KILOMETERS AWAY

Using the Deep Space Network’s (DSN) 70-meter-wide Goldstone solar array radar, called Deep Space Station 14 (DSS-14) in California, JPL scientists transmitted radio waves to the asteroid and received the reflected signals back from the same antenna. In addition to determining that the asteroid is roughly spherical, they discovered that it is a binary system: A smaller asteroid, or moonlet, orbits it from a distance of about 3 kilometers.

“About two-thirds of asteroids of this size are thought to be 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 on how they may have formed“said Lance Benner, a JPL senior scientist who helped lead the observations.

Two days later, on June 29, the same team observed asteroid 2024 MK pass by our planet from a distance of just 295,000 kilometers, or a little more than three-quarters of the distance between the Moon and Earth. This asteroid, about 150 meters wide, appears to be elongated and angular.with prominent flat and rounded regions. For these observations, the scientists also used DSS-14 to transmit radio waves to the object, but they used Goldstone’s 34-meter DSS-13 antenna to receive the signal that bounced off the asteroid and returned to Earth. The result of this “bistatic” radar observation is a detailed image of the asteroid’s surface, revealing concavities, ridges and rocks about 10 meters wide.

Close approaches by near-Earth objects the size of 2024 MK are relatively rare, occurring about every two decades on average, so the JPL team sought to gather as much data on the object as possible. “This was an extraordinary opportunity to investigate the physical properties and obtain detailed images of a near-Earth asteroid,” Benner said.

Asteroid 2024 MK was first reported on June 16 by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) at the Sutherland Observing Station in South Africa. Its orbit was altered by Earth’s gravity as it passed by, reducing its 3.3-year orbital period around the Sun by about 24 daysAlthough it is classified as a potentially hazardous asteroid, calculations of its future motion show that it does not pose a threat to our planet in the foreseeable future.