Free Republic

Sunday is International Asteroid Day, commemorating the Earth's largest recorded asteroid impact while focusing on the real danger of asteroids that could collide with Earth. In 1908, a powerful asteroid struck the Podkamennaya Tunguska River area in a remote Siberian forest of Russia. Six years ago, an asteroid entered Earth's atmosphere over Chelyabinsk, Russia. It exploded in the air, releasing 20 to 30 times more energy than that of the first atomic bombs and generating brightness greater than the sun. It damaged more than 7,000 buildings and injured more than 1,000 people. The shock wave broke windows 58 miles away....

Within the space of less than an hour on September 5, the Mount Lemmon Survey discovered two objects which will both pass by the Earth on September 8 at a distance closer than the Moon! This unprecedented coincidence provides an exciting observing challenge for amateurs although those observing from the UK will not have the best views. The intrinsically smaller object, 2010 RF12, will be the more favourable observing target in that it passes closest at about 0.21 lunar-distance, i.e. about 80,000 km. Tonight from the UK (Sep 6/7) this object will be 17th magnitude but by tomorrow (Sep 7/8)...