Near-Earth Objects are comets and asteroids that have been pushed by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth's neighborhood. They are about 4.5 billion years and can range in size from pebbles or lumps of ice, to rocky or icy worlds nearly 1,000 kilometers across. An asteroid or comet may become a Near Earth Object when its trajectory intersects the orbit of the Earth or is within 0.3 Astronomical Units (…showed first 75 words of 644 total…

…showed last 75 words of 644 total…