![]() This heat nudge was named after the Polish civil engineer who first described it in 1901: Ivan Osipovich Yarkovsky. “The one that’s most sizeable is Yarkvovsky.” “There are a lot of factors that might affect the predictability of Bennu’s trajectory in the future, but most of them are relatively small,” says William Bottke, an asteroid expert at the Southwest Research Institute in Boulder, Colorado, and a participating scientist on the OSIRIS-REx mission. Having nothing to do with gravity, the Yarkovsky effect sways Bennu’s orbit because of heat from the Sun. There’s another phenomenon nudging Bennu’s orbit and muddying future impact projections. ![]() ![]() “And yet, after that encounter in 2135, we really can’t say exactly where it is headed.” “Right now, Bennu has the best orbit of any asteroid in our database,” Chesley said. This will be Bennu’s closest approach to Earth over the five centuries for which we have reliable calculations. By 2135, when Bennu’s shifted orbit is expected to bring it closer than the Moon, its flyby window grows wider, to 160,000 kilometers (nearly 100,000 miles). A very small difference in position within that window will get magnified enormously in future orbits and make it increasingly hard to predict Bennu’s trajectory.Īs a result, when this asteroid comes back near Earth in 2080, according to Chesley’s calculations, the best window we can get on its whereabouts is 14,000 kilometers (nearly 9,000 miles) wide. But it could pass at any point in a 30-kilometer (19-mile) window of space. In 2060, Bennu will pass Earth at about twice the distance from here to the Moon. As a result, the uncertainty about where the asteroid will be each time it loops back around the Sun will grow, causing predictions about Bennu’s future orbit to become increasingly hazy after 2060. That’s close enough that Earth’s gravity will slightly bend Bennu’s orbital path as it passes by. ![]() Given these parameters, astronomers can predict the next four exact dates (in September of 2054, 2060, 20) that Bennu will come within 7.5 million kilometers (5 million miles or. Their predictions are informed by ground observations and mathematical calculations that account for the gravitational nudging of Bennu by the Sun, the Moon, planets and other asteroids, plus non-gravitational factors. Scientists have estimated Bennu’s trajectory around the Sun far into the future. Why Bennu’s future trajectory predictions get fuzzy “We know within a few kilometers where Bennu is right now,” said Steven Chesley, senior research scientist at CNEOSand an OSIRIS-REx team member whose job it is to predict Bennu’s future trajectory. They’ve turned their optical, infrared and radio telescopes toward the asteroid every time it came close enough to Earth, about every six years, to deduce features such as its shape, rotation rate and trajectory. Even so, astronomers want to know exactly where Bennu is located at all times.Īstronomers have estimated Bennu’s future trajectory after observing it several times since it was discovered in 1999. Put another way, those odds mean there is a 99.963 percent chance the asteroid will miss the Earth. Asteroid experts at the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory in Pasadena, California, project that Bennu will come close enough to Earth over the next century to pose a 1 in 2,700 chance of impacting it between 21. If it impacted Earth, Bennu would cause widespread damage. How scientists predict Bennu’s whereaboutsĪbout a third of a mile, or half a kilometer, wide, Bennu is large enough to reach Earth’s surface many smaller space objects, in contrast, burn up in our atmosphere. Here is how the OSIRIS-REx mission will support this work: As they collect the most detailed information yet about the forces that move asteroids, experts from NASA’s Planetary Defense Coordination Office, who are responsible for detecting potentially hazardous asteroids, will improve their predictions of which ones could be on a crash-course with our planet. Scientists studying the rock through OSIRIS-REx’s instruments in space will also shape our future. Generations of planetary scientists will get to study pieces of the primitive materials that formed our cosmic neighborhood and to better understand the role asteroids may have played in delivering life-forming compounds to planets and moons.īut it’s not just history that the mission to Bennu will help uncover.
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