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https://www.yahoo.com/news/nasa-boosts-impact-risk-potentially-220546594.html

Potentially hazardous asteroid Bennu just became slightly more potentially dangerous.

Over a century from now, in 2135, a half-kilometre-wide asteroid named 101955 Bennu will pass between the Earth and the Moon. While there is absolutely no chance of an impact with Bennu at that time, the close encounter throws uncertainty into the predictions. As a result, there's no saying for sure that Earth will be safe from Bennu afterward.

Before NASA sent their OSIRIS-REx spacecraft to Bennu, astronomers tracked asteroid Bennu using telescopes. Their observations gave us very accurate calculations of Bennu's orbit. The relatively close passes of Bennu in 1999, 2005 and 2011 helped with this. Although it was officially classified as a "Potentially Hazardous Asteroid" (PHA), NASA could rule out any possibility of a Bennu impact for the next 100+ years.

However, the September 2135 encounter added an extra complication. The asteroid comes very close to Earth at that time. On September 24 of that year, its absolute minimum distance could be around 110,000 km from the planet's surface or less than one-third the distance to the Moon. As it flies past, it will encounter one of several 'gravitational keyholes'. As it passes through one of these tiny points in space, Earth's gravity will tug on the asteroid and alter its orbit around the Sun.