Scientists have found 40,000 asteroids that could hit Earth. But it's just the tip of the iceberg

Astronomers have announced they've catalogued the 40,000th near-Earth asteroid.

The announcement marks a milestone in the detection of space rocks that orbit close to Earth and, scientists say, highlights the threat posed by space rocks to our home planet.

Near-Earth asteroids can range from a few metres to several kilometres across and travel on orbits that bring them relatively close to Earth.

This makes them objects of immense interest to both scientists and planetary defence experts.

An asteroid is a rocky remnant left over from the Solar System’s formation over 4 billion years ago.

Most asteroids in our Solar System are found in the main asteroid belt between Mars and Jupiter.

But a near-Earth asteroid has an orbit that brings it within about 45 million kilometres (28 million miles) of Earth’s orbit.