Large asteroid passes by Earth
DOI: 10.1063/PT.5.028594
BBC : On Monday asteroid 2004 BL86 traveled past Earth at a comfortably safe distance of 1.2 million km, about three times as far away as the Moon. In its wake was its own small moon. At 325 m wide, the asteroid is a fairly large one. Although it could cause considerable damage, including mass extinctions, were it to hit Earth, an asteroid of that size doesn’t pass by often. The next is not expected until 2027. Because of the risk, however, scientists have been working to identify and track all asteroids at least 1 km in size. Sky surveys indicate that more than 90% of them have probably been located. Smaller asteroids, of which there could be tens of thousands, pose much less risk because they tend to disintegrate high in Earth’s atmosphere.