Asteroid Didymos and its small moonlet Dimorphos make up a binary asteroid system. The small moon (Dimorphos) orbits the larger body (Didymos). The two asteroids are not a threat to Earth, but since they pass pretty close to Earth, they were chosen as the target for NASA’s DART mission (Double Asteroid Redirection Test). It will be NASA’s first mission testing planetary defense technology. This technology could one day deflect hazardous asteroids on a collision course with Earth.
DART impacted Dimorphos on Sept. 26, 2022, and on Oct. 11, 2022, NASA announced that DART successfully altered the smaller asteroid’s orbit. This marked the first time humanity had purposely changed the motion of a celestial object, and it was the first full-scale demonstration of asteroid deflection technology.
Didymos, the larger asteroid of the pair is about a half mile (780 meters) in diameter. The moonlet, Dimorphos, is about 525 feet (160 meters) in diameter. As it orbits the Sun, the asteroid pair comes close to Earth’s orbit, occasionally approaching relatively close to our planet.
The orbit of Didymos ranges from just outside the orbit of Earth (about 1 AU) to a bit beyond the orbit of Mars (about 2.27 AU) and is slightly inclined by about 3 degrees. It takes 2.11 Earth years for each trip around the Sun. Didymos is classified as a member of the Amor group of asteroids, named after asteroid 1221 Amor. Didymos spins rapidly, rotating about once every 2.26 hours. The DART investigation team confirmed the spacecraft’s Sept. 26, 2022, impact altered Dimorphos’ orbit around Didymos by 32 minutes, shortening the 11-hour and 55-minute orbit to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus or minus 2 minutes.
RELATED STORIES
https://science.nasa.gov/solar-system/asteroids/didymos/
https://www.jpl.nasa.gov/news/nasa-study-asteroids-orbit-shape-changed-after-dart-impact/
https://www.esa.int/Space_Safety/Hera/Target_asteroid2
https://www.sciencedirect.com/science/article/abs/pii/S0019103524000551
https://www.space.com/dart-asteroid-mission-didymos-dimorphos-age-origins
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