The asteroid is estimated to be 2,000 to 4,500ft wide, and qualifies as a 'near Earth object'.

NEA (near-Earth asteroid) 2002 AM31 is described as 'the size of a city block'.

Astronomers say not to panic - it will pass through space 14 times further from Earth than the Moon.

On Sunday, July 22, we will have a live feed from the Slooh Space Camera. The show will start at 4:30 p.m. Pacific (7:30 Eastern) with images from the Slooh telescope in the Canary Islands. For all the latecomers, another telescope in Arizona will start tracking the asteroid at around 8 p.m. Pacific (11 Eastern) as well. Slooh will have discussion with Astronomy magazine columnist Bob Berman, astronomer Matt Francisco from Prescott Observatory, and their own Patrick Paolucci.

The asteroid, known as 2002 AM31 was discovered 10 years ago by Lincoln Near Earth Asteroid Research (LINEAR). It is a fairly large near-Earth asteroid — about 3,000 feet wide — and will come within about 3.2 million miles of Earth, or roughly 14 times the Earth-moon distance. This comes on the heels of another large asteroid, 2012 LZ1, which flew by at a similar distance on June 14. Because of its size and distance, 2002 AM31 is classified as “potentially hazardous,” though it has zero chance of hitting Earth.

Viewers with a Pinterest account can take their own images of the asteroid using Slooh’s feed. While the asteroid won’t be much more than a blip on the screen, it will whiz by a background of beautiful stars.
SOURCE

Hurtling through space: The asteroid is estimated to be 2,000 to 4,500ft wide, and qualifies as a 'near Earth object' (Source)