On June 27, asteroid 2011 UL21 made a comparatively shut encounter with Earth, flying by our planet at a distance of 6.6 million kilometers (4.1 million miles), or roughly 17 occasions the typical distance from the Earth to the Moon.Whereas not shut sufficient to fret about, the encounter gave astronomers a possibility to get a better take a look at the item. Doing so may also help us be taught extra about such asteroids, in addition to slim down their orbit, permitting us to know whether or not they are going to pose dangers to the planet additional sooner or later. “The time period ‘Doubtlessly Hazardous Asteroid’ (PHA) is a exact formal definition, referring to minor planets bigger than roughly 140 meters [459 feet] that may come inside 7.5 million km [4.6 million miles] from the Earth,” Gianluca Masi, astrophysicist and scientific director of the Digital Telescope Mission, stated in an announcement forward of the flyby. “In different phrases, solely the biggest asteroids able to approaching shut sufficient to our planet are flagged as PHAs, which doesn’t imply they’ll hit the Earth, however they nonetheless warrant a greater monitoring.”Throughout this 12 months’s flyby, NASA’s Deep Area Community’s Goldstone planetary radar stored a detailed watch on 2011 UL21, imaging it seven occasions because it handed at 25 kilometers (16 miles) per second. This was the primary likelihood that NASA needed to picture the asteroid utilizing radar, and once they did so they found the asteroid is definitely a binary system. The asteroid has its personal moonlet, orbiting at a distance of about 1.9 miles (3 kilometers).“It’s thought that about two-thirds of asteroids of this measurement are binary programs, and their discovery is especially essential as a result of we will use measurements of their relative positions to estimate their mutual orbits, lots, and densities, which give key details about how they could have shaped,” Lance Benner, principal scientist at JPL who helped lead the observations, stated in an announcement.The moonlet could be seen on the backside of those radar photographs.NASA/JPL-CaltechDuring the method, NASA found that the asteroid is roughly spherical. Previous to radar imaging, there was uncertainty concerning the object’s measurement, with estimates suggesting it could possibly be as small as 1.7 kilometers and as massive as 3.9 kilometers (1.05 to 2.4 miles). After radar imaging, NASA places its measurement at almost 1 mile broad (1.5 kilometers) broad, so just a little smaller than anticipated.It was truly a reasonably busy week for the radar system, which observes area objects by transmitting radio waves after which receiving the mirrored sign again to the identical antenna. On June 29, a second object – solely found on June 16 – made a a lot nearer method, passing inside 184,000 miles (295,000 kilometers) of Earth. That is just a little over three-quarters of the typical distance between the Earth and the Moon, a reasonably shut method by the asteroid provisionally named 2024 MK. Asteroid 2024 MK, tumbling via area.Picture credit score: NASA/JPL-Caltech”For these observations, the scientists additionally used DSS-14 to transmit radio waves to the item, however they used Goldstone’s 114-foot (34-meter) DSS-13 antenna to obtain the sign that bounced off the asteroid and got here again to Earth,” NASA defined. “The results of this ‘bistatic’ radar statement is an in depth picture of the asteroid’s floor, revealing concavities, ridges, and boulders about 30 toes (10 meters) broad.”The asteroid’s path was altered barely by Earth’s gravity, shortening its 3.3-year orbit across the Solar by about 24 days. The asteroid, which was found by NASA-funded Asteroid Terrestrial-impact Final Alert System (ATLAS) simply 13 days earlier than its closest method, is classed as doubtlessly hazardous. Nonetheless, calculations of its orbit present that it poses no menace to Earth for the foreseeable future.