Nanjing (CNS) -- "Small asteroid 2011MD will fly by Earth at 0:50 am today, but it won't hit," said Zhao Haibing, researcher from the Purple Mountain Observatory in Nanjing, Jiangsu Province.
Zhao explained that with a size of about five railway carriages, asteroid 2011MD will pass by Earth with only about 12,000 miles (about half the Earth's circumference) to spare.
Zhao said: "The gravity of Earth will change the little asteroids' tracks when it gets close. Due to the uncertainty of how much the tracks will alter, it's hard to tell the nearest part of Earth 2011MD will pass by."
Currently, there are more than 8,000 near-Earth asteroids (NEAs) in the solar system, and more than 1,000 of them pose threats to Earth (PHAs). The "warning limit line" between Earth and NEAs is about 4.66 million meters, or 0.05 astronomical units.
Zhao explained that NEAs with a diameter longer than 6.2 miles, can destroy Earth if they hit; NEAs with a diameter longer than 0.62 miles, can destroy a continent if they hit; and NEAs with a diameter longer than 100 meters can destroy a thousand square meters of land if they hit Earth.
"This year, we have found that a dozen NEAs that may harm Earth, and there are some we only just saw. It's important to keep an eye on them," Zhao added.
He also said that it's impossible for mankind to alter asteroids’ tracks.
