NASA just announced an unexpected asteroid flyby October 31. Our closest flyby of this size since 2006.

It’s time to get to know a new friend: asteroid 2015 TB145, a sizeable chunk of rock that’s hurtling through space at speeds of over 126,000 km/h (78,293 mph) right now. Discovered just 10 days ago, the asteroid has caught the attention of scientists at NASA because on October 31, it’s expected to draw closer to Earth than anything this size has since July 2006.
But before you reach for the keys to your apocalypse bunker, relax. When we say "close", we’re talking relatively, which in this case means 1.3 lunar distances, or about 499,000 km (310,000 miles) from Earth.
"This is the closest approach by a known object this large until 1999 AN10 approaches within 1 lunar distance in August 2027," a NASA report states. "The last approach closer than this ... was by 2004 XP14 in July 2006 at 1.1 lunar distances."
Detected on October 10 by the Pan-STARRS I survey in Hawaii, which employs several astronomical cameras and telescopes from around the world to identify potentially threatening near-Earth objects, asteroid 2015 TB145 is estimated to be between 280 to 620 metres (918 to 2,034 ft) in diameter.