\n While Earth wouldn\u2019t face any significant physical danger if the building-size asteroid struck the moon, researchers suggested that any astronauts or infrastructure on the lunar surface at the time could be at risk<\/a> \u2014 as could satellites that we depend on to keep vital aspects of life, including navigation and communications, running smoothly.\n <\/p>\n \n Astronomers didn\u2019t expect to get a chance to better assess the risk of a YR4 lunar impact until the asteroid came back into view from Earth\u2019s perspective in 2028. However, Dr. Andy Rivkin, planetary astronomer from the Johns Hopkins University\u2019s Applied Physics Laboratory in Maryland, and Julien de Wit, associate professor of planetary science at the Massachusetts Institute of Technology, spied an opportunity for an earlier glimpse.\n <\/p>\n \n Rivkin and de Wit applied and received approval to use the James Webb Space Telescope, or JWST, the only observatory with a chance of spotting the asteroid before 2028.\n <\/p>\n \n Their observations, taken on February 18 and 26, improved the certainty of the asteroid\u2019s future position. Rather than colliding with the moon, YR4 will pass it from a relatively close distance of 14,229 miles (22,900 kilometers) \u2014 narrowly ruling out a once-in-a-lifetime lunar impact that humanity would have witnessed.\n <\/p>\n \n Rivkin and de Wit\u2019s Webb observations were among the faintest ever made of an asteroid, according to NASA<\/a> and the European Space Agency<\/a> \u2014 and the detections weren\u2019t easy to come by given the narrow window of time to capture them.\n <\/p>\n \n As the most powerful space telescope, Webb is perhaps a natural choice to aid the search for a potentially dangerous asteroid that could impact Earth or the moon. But YR4 presented a challenge.\n <\/p>\n \n The researchers had to develop new techniques for using Webb\u2019s instruments to detect the asteroid as a nearly invisible speck amid the vastness of space, and their innovations could help future efforts if another similar threat arises.\n <\/p>\n \n Scientists have used Webb to observed a multitude of celestial wonders \u2014 many of them on a grand scale \u2014 since the telescope\u2019s first images were released in the summer of 2022. Sprawling galaxies and cosmic structures that expand for light-years<\/a> have often been the focus of the observatory\u2019s infrared gaze, but so have distant, faint objects.\n <\/p>\n \n A team led by de Wit demonstrated in December 2024 that Webb was capable of spotting 138 new asteroids<\/a> ranging from bus- to stadium-size in the main asteroid belt located between the orbits of Mars and Jupiter that were not observable with ground-based telescopes. The finding showed that Webb could study extremely faint objects in the solar system, de Wit said.\n <\/p>\n \n When it was time to focus on YR4, de Wit and Rivkin leaned into Webb\u2019s capability as a planetary defense tool \u2014 except the challenge was greater.\n <\/p>\n \n YR4 is about 60 meters (about 200 feet) in diameter and in February was located millions of miles from Webb\u2019s orbit, which for de Wit and Rivkin was like looking for a dust particle against a backdrop of blinking stars.\n <\/p>\n \n Previous Webb observations of YR4 had helped to determine the space rock\u2019s size in the spring of 2025. However, the asteroid appeared even fainter through the telescope\u2019s instruments last month, reflecting as much light as a single almond would at the distance of the moon, according to de Wit and Rivkin in a NASA release.\n <\/p>\n \n Webb\u2019s sensitivity and stability, as well as its ability to accurately track moving targets, make it an excellent tool for making hours-long observations of YR4, they noted.\n <\/p>\n \n Capturing images of the faint asteroid against bright stars required a novel approach to using the telescope\u2019s Near-Infrared Camera, which is normally used to study extremely distant galaxies or exoplanets that appear fixed, rather than moving. YR4, on the other hand, moves much more quickly when compared with distant stars.\n <\/p>\n \n Rivkin and de Wit\u2019s team knew they only had a couple of five-hour windows to secure the observations in February due to the slim chances of YR4 appearing just bright enough to be detectable, as well as the restrictions around the direction in which Webb could look without interference from sunlight.\n <\/p>\n \n Dr. Artem Burdanov, team member and research scientist at the MIT department of Earth, Atmospheric and Planetary Sciences, identified the two brief observation windows with the best chances of seeing YR4 with Webb, Rivkin noted.\n <\/p>\n \n The techniques employed during the observations were a blend of ideas the team developed in advance, as well as those that couldn\u2019t be tested until the data was streaming in during the observations, requiring the astronomers to adapt quickly in the moment, Rivkin said.\n <\/p>\n \n \u201cTo observe the asteroid we designed an observing strategy that allowed JWST to track a fast-moving target while still preserving extremely precise astrometry, meaning measurements of the object\u2019s position relative to background stars,\u201d de Wit said.\n <\/p>\n \n Carefully timed exposures enabled the team to detect the asteroid, which was 4 billion times fainter than what the naked eye can see and 20 to 30 times fainter than the smallest asteroids detectable with other observatories, de Wit said. The timing also meant that the precisely known position of the stars visible behind YR4 acted like a reference, allowing the astronomers to track the asteroid\u2019s position with extreme accuracy.\n <\/p>\n \n Three independent analyses of the observations were made by different members of the team, and despite varying approaches they all agreed very well, Rivkin said.\n <\/p>\n \n \u201cIn effect, we adapted an instrument optimized for deep cosmological imaging into a precision tracker for a rapidly moving asteroid, which is quite different from its usual use,\u201d de Wit explained.\n <\/p>\n \n A paper detailing the observations and techniques will soon be available, he added.\n <\/p>\n![\"A](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/03\/asteroid-2024-yr4.jpg\")
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