from www.iflscience.com
An asteroid flew pretty close to Earth last week. It missed us, you may have noticed. But we didn’t spot it until three days after it had flown past, which is a pretty terrifying reminder about the dangers asteroids pose to our world. Asteroid 2017 001 was about 37 to 77 meters (121 to 252 feet) across. It came about a third as close as the Moon, 123,031 kilometers (76,448 miles) from our planet, which is a pretty safe distance. It flew past at some point in the night of July 20 at a speed of about 10.36 kilometers (6.4 miles) per second. However, it was not until July 23 that we spotted the asteroid, after it had passed Earth, thanks to the ATLAS-MLO telescope in Hawaii. That’s, you know, not great. “Asteroid 2017 OO1 is an important reminder that we need to do a better job at detecting even small-sized asteroids early,” Grigorij Richters, the founder of Asteroid Day that seeks to raise awareness about asteroids, told IFLScience. “Small asteroids can cause significant regional damage and we are the only species that can do something about this cosmic hazard. Just ask the dinosaurs!”
read the rest of the article here: http://www.iflscience.com/space/an-asteroid-just-skimmed-earth-but-we-didnt-spot-it-until-three-days-later/