Astronomers are tracking a 250-meter-wide asteroid called

Astronomers are tracking a 250-meter-wide asteroid called Apophis which will come within 30,000 km of earth in 2029. However, it’s too soon to tell if that near-miss will pull the asteroid into a collision course with the earth 7 years later. “Lu says the best way to deflect an asteroid is with a ‘gravity tractor’ — a spacecraft displacing about 1 metric ton that simply hovers near an asteroid and gently tweaks its orbit.”

• astronomy