What they uncovered was a surprise - Asteroid 2012 LZ1 is actually bigger than thought, in fact, it is quite a lot bigger.
With the help of Arecibo, astronomers have deduced that Earth will be safe from being hit by 2012 LZ1 for at least 750 years.
The near-Earth asteroid 2012 LZ1, which astronomers think is about 1,650 feet (500 meters) wide, will come within 14 lunar distances of Earth Thursday evening.
The online skywatching service will train a telescope on the Canary Islands on 2012 LZ1 and stream the footage live, beginning at 8:00 p.
2012 LZ1 was discovered on the night of June 10-11 by Rob McNaught and his colleagues, who were peering through the Uppsala Schmidt telescope at Siding Spring Observatory in Australia.