Humanity emits a sigh of relief when any huge space asteroid flies past Earth - except, perhaps, small asteroids, which scatter the precious meteorites on the surface of the earth. But when one of the approximately 4,700 potentially hazardous asteroids (PHA) bypassing us, we really should consider themselves lucky - these asteroids could kill us.
PHA - asteroids, of a width of 100 meters (330 feet), which drift close enough to the Earth’s orbit. Many astronomers consider them a threat. They are within eight million kilometers (five million miles), or about 20 distance from the Earth to the Moon from Earth, and if they are close enough to the Earth, they will be able to survive the destruction of the atmosphere and destroy the whole city, and to be maybe worse. They - a special subset of a larger family of near-Earth asteroids - NEA.V currently mission began researching and assessing the degree of danger 4,700 (plus or minus 1500), a class of asteroids PHA. Literally, the mission is called near-Earth object-hunting mission or just NEOWISE.
There is no real surprise in such a number of potentially dangerous asteroids - in fact, this number is the same as with most previous estimates - but for the mission were selected NEOWISE 107 PHA certain asteroids that, based on them, to give a more accurate estimate of the total number of dangerous asteroids in the neighborhood of the earth . There is an assumption that only 20-30 percent of these asteroids have been discovered to date.