At 6.3 million kilometers apart, an asteroid will fly across the earth without threat

　　6.3 million kilometers apart

　　An asteroid will fly across the earth without threat

　　Science and Technology Daily, Beijing, April 28 (Reporter Liu Xia) According to the US Space Network reported on the 28th, the large asteroid 1998 OR2 will fly over the earth in the early morning of April 29, US time, when it is 6.3 million kilometers away from the earth. Scientists emphasized that in the context of the visible universe more than 90 billion light-years wide, this is also considered "intimate contact", but this time the probability of this asteroid hitting the earth is zero.

　　In 1998, the OR2 was 2.4 kilometers wide. The distance when flying across the earth did not exceed 6.3 million kilometers, which was 16 times the average distance between the moon and the earth (385,000 kilometers).

　　Paul Jordas, the manager of the NASA Jet Propulsion Laboratory's Near-Earth Object Research Center, said in the "NASA Science Scene" show: "We have discovered and tracked 90% of Near-Earth Asteroids (NEA), The width of these asteroids is at least 1 km. Some asteroids are very large, but in the foreseeable future, the possibility of large asteroids hitting the earth is very small, at least not on our current list. "

　　However, he and Linda Johnson, the project director of the NASA Planetary Defense Coordination Office, both emphasized that there are a large number of NEAs in space, and there may still be some dangerous asteroids that have not yet been discovered.

　　They pointed out that asteroids often collide with each other and may also be affected by the gravity of other celestial bodies, making it difficult for scientists to simulate their long-term orbits. Some asteroids may hit the earth violently, which is believed to be one of the reasons for the extinction of dinosaurs on Earth. This makes it extremely important to discover and track asteroids. Humans are not as helpless as dinosaurs. If we can find dangerous asteroids in advance, we can take corresponding measures to deal with them.

　　Jordas said that if humans find an asteroid to attack 5-10 years in advance, they can carry out a kinetic energy collision deflection mission-sending a spacecraft to hit a dangerous asteroid to deflect its orbit; if we have a longer time, we A non-violent "gravitational tractor" method can be used to slowly push the asteroid away from the Earth with the probe. If we do n’t have time, we may use extremely violent nuclear explosion methods.