The Dimorphos moonlet is one of the smallest astronomical objects to receive a permanent name and is one of 27,500 known near-Earth asteroids of all sizes tracked by NASA. Smaller asteroids are far more common and present a greater theoretical concern in the near term, making the Didymos pair suitable test subjects for their size, according to NASA scientists and planetary defense experts.Īlso, the two asteroids' relative proximity to Earth and dual configuration made them ideal for the DART mission. Launched by a SpaceX rocket in November 2021, DART made most of its voyage under the guidance of flight directors on the ground, with control handed over to the craft's autonomous on-board navigation system in the final hours of the journey.ĭimorphos and Didymos are both tiny compared with the cataclysmic Chicxulub asteroid that struck Earth some 66 million years ago, wiping out about three-quarters of the world's plant and animal species including the dinosaurs. The impact blasted tons of rocky material from the asteroid's surface into space, visible in telescope images as a large debris plume, producing a recoil effect that added to the force exerted on Dimorphos from the collision itself, NASA said. The relatively loose composition of rubble that Dimorphos appears to consist of may be a factor in how much the asteroid was budged by DART's blow. So the actual change of more than a half hour, with a margin of uncertainty plus or minus two minutes, exceeded expectations. Scientists had predicted the DART impact would shorten Dimorphos' orbital path by at least 10 minutes but would have considered a change as small as 73 seconds a success. Neither of the two asteroids involved, nor DART itself, short for Double Asteroid Redirection Test, posed any actual threat to Earth, NASA scientists said.īut Nancy Chabot, DART's coordination lead at APL, said Dimorphos "is a size of asteroid that is a priority for planetary defense."Ī Dimorphos-sized asteroid, while not capable of posing a planet-wide threat, could level a major city with a direct hit. The outcome "demonstrated we are capable of deflecting a potentially hazardous asteroid of this size," if it were discovered well enough in advance, said Lori Glaze, director of NASA's planetary science division. Tom Statler, DART program scientist for NASA, said the collision also left Dimorphos "wobbling a bit," but additional observations would be necessary to confirm that. The test flight concluded with the DART impactor vehicle, no bigger than a refrigerator, slamming directly into Dimorphos at about 14,000 miles per hour (22,531 kph).Ĭomparison of pre- and post-impact measurements of the Dimorphos-Didymos pair as one eclipses the other shows the orbital period was shortened to 11 hours, 23 minutes, with the smaller object bumped tens of meters closer to its parent. Last month's impact, 6.8 million miles (10.9 million km) from Earth, was monitored in real time from the mission operations center at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, where the spacecraft was designed and built for NASA.ĭART's celestial target was an egg-shaped asteroid named Dimorphos, roughly the size of a football stadium, that was orbiting a parent asteroid about five times bigger called Didymos once every 11 hours, 55 minutes. "It felt like a movie plot, but this was not Hollywood." The telescope observations can also shed light on how much material was released from the asteroid’s surface at the moment of impact and how quickly it was ejected.īoth telescopes view the universe in different wavelengths of light, which can show if the cloud of material was just full of dust or included larger chunks of rock."This is a watershed moment for planetary defense and a watershed moment for humanity," NASA chief Bill Nelson told reporters in announcing the results. The Webb and Hubble images can be used to learn more about the surface of Dimorphos, which had never been seen until these detailed views collected by DART streamed back from the spacecraft on Monday. While neither Dimorphos nor Didymos, the larger asteroid it orbits, pose a threat to Earth, the double asteroid system was a perfect target for the DART spacecraft to attempt to change the motion of an asteroid slightly. The observatories were both witness to humanity’s first test of asteroid deflection technology. The James Webb Space Telescope and the Hubble Space Telescope captured images of the moment when the Double Asteroid Redirection Test, or DART, spacecraft crashed into Dimorphos on Monday. Two of the most powerful telescopes in space watched as a NASA spacecraft intentionally slammed into an asteroid this week.
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