Asteroid RM20 makes the closest approach to earth today!

NASA Provides some data, see below,  where we can see the time of closest approach is 10:29 GMT.

Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.

On September 20, 2016 there were 1730 potentially hazardous asteroids. 

Recent & Upcoming Earth-asteroid encounters:

Asteroid	Date(UT)	Miss Distance	Size
2016 QL44	Sep 17	3.6 LD	42 m
2016 QS11	Sep 18	12.2 LD	29 m
2016 RM20	Sep 20	6.2 LD	25 m
2009 UG	Sep 30	7.3 LD	101 m
2100 Ra-Shalom	Oct 9	58.3 LD	1.1 km
2014 UR	Oct 18	12 LD	21 m
2005 SE71	Oct 24	72.2 LD	1.0 km
2003 TL4	Oct 27	10.1 LD	565 m

Notes: LD means "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. MAG is the visual magnitude of the asteroid on the date of closest approach.

http://www.spaceweather.com/