Mikael Granvik from the University of Helsinki in Finland, along with his colleagues run a computer simulation, to find the frequency of various near-Earth asteroids, and their likelihood of being caught gravity when approached. To be caught, an object must start out of the orbit is quite identical with the Earth. Team estimates that, on average, an asteroid with a size of 1 yard or 1,000 space rock measuring approximately 4 inches, may be orbiting the Earth.
"There's a lot more than people might think," said Mikael Granvik. These asteroids, generally stay in orbit around the Earth for less than one year. Although the simulations were done by researchers, also expressed some asteroids may have stayed longer.