An asteroid passes close to the Earth and no one even noticed

At the beginning of the week, an asteroid of a not so negligible size discovered two days ago, has buzzed us at a distance less than the half that separating us from the Moon.

It will be customary to say that this asteroid has "buzzed" the Earth. In fact, asteroid 2017 AG13 approached at a distance of 0.5 times the distance from Earth to the Moon, or 0.0014 times the distance from Earth to the Sun.

This represents between 192 000 and 210 000 km. rather comfortable even if the "close" passage took place only two days after the discovery of the asteroid by the Catalina Sky Survey (University of Arizona).

According to data from the Near-Earth Object Program of the Jet Propulsion Laboratory (NASA), 2017 AG13 spun at a speed of 15.7 km/s, of an estimated diameter of 16 and 37 meters, it passed close to us on Monday January 9 at midday.

This is not the first time that an approaching asteroid is spotted late. In this case, the discovery by telescopes was made difficult by the 2017 AG13 speed and its low luminosity. The Slooh Observatory made a comparison with the Chelyabinsk meteor. With a diameter of 15 to 17 meters, it had penetrated our atmosphere over Russia in 2013 and had caused material damage.

Asteroids, which can pose a threat to the Earth on a global scale, have a priori been discovered for the most part. Last year, NASA launched the OSIRIS-REx mission that will study the Bennu asteroid and bring back samples. With a diameter of the order of 500 meters, it has a chance on 2,700 to hit the Earth between 2175 and 2199.

According to the list of impact risks of the US space agency and current observations, an asteroid of 1.3 km in diameter will approach Earth in 2880. There is one chance in 8,330 that it strikes the Earth. By way of illustration, the meteorite probably responsible for the extinction of dinosaurs was 10 km in diameter.

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