The 24 - 54 metre wide asteroid 2007 RJ1 will make a close pass (58.5 lunar distances, 0.1504 AU), travelling at 13.73 km/second, to the Earth-Moon system on the 4th September 2014 @ 06:27 UT ±1 day 05:11.
On September 16th Asteroid 2007 RJ1 will pass 972,385 km (0.0065 AU) from Earth. That's 2.5 times the distance to the Moon. It should get as bright as 16th Magnitude. Its estimated diameter is 24 - 50 metres. As the asteroid pasts Earth with an apparent motion on the 16th of 117.5"/minute (10:00 PM) to 123.5"/minute (5:00 AM), it is travelling at a velocity relative to the Earth of 9.82 km per second.