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The moon has been orbiting Earth for more than four billion years.

But our planet's faithful companion may not be alone. A new object, dubbed 2014 OL339, has been found masquerading as Earth's 'second moon'.

The new 'moon', which is in fact a 490ft (150 metre) asteroid, takes about a year to orbit the sun and is close enough to Earth to look like its satellite.

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A new object, dubbed 2014 OL339, has been found masquerading as Earth's 'second moon'.The new 'moon', which is in fact a 490ft (150 metre) asteroid, takes about a year to orbit the sun and is close enough to Earth to look like its satellite. Pictured is its elliptical orbit

The peculiar object was accidentally discovered on July 29 by astronomer Farid Char of the Chilean University of Antofagasta.

According to Rebecca Boyle writing in New Scientist, 2014 OL339 has been travelling near to our planet for about 775 years and it will continue to do so for another 165 years.

It has an elliptical orbit and takes around 364.92 days to circle the sun once, meaning the asteroid and Earth are in 'resonant orbits'.

This happens when two orbiting bodies exert a gravitational influence on each other due to their orbits being closely related.

For instance, Pluto and Neptune are in an orbital resonance of 2:3. This means for every two times Pluto goes around the sun, Neptune makes three trips around the star.

A number of other space rocks have fallen into orbits that make them look as though they are circling the Earth. The most famous is 3753 Cruithne, a 3 miles (5km) asteroid (animations shown above). The yellow orbit in the top animation shows Cruithne's orbit around Earth 

Asteroid 2014 OL339 orbits the sun in a similar timeframe to Earth, but our planet's gravity pushes it into an eccentric wobble.

Looking up with powerful telescopes from Earth, OL339 appears as though it is in orbit around our planet, moving backwards relative to the stars.

A number of other space rocks have fallen into orbits that make them look as though they are circling the Earth.

Like 2014 OL339, many of these take around one year to orbit the sun in elliptical orbits, according to Phil Plait writing in the Bad Astronomy blog.

The most famous is 3753 Cruithne, a three-mile (5km) asteroid that was discovered in 1986. However, it wasn't until 1997 that scientists uncovered its unusual path.

Our planet has also had a number of 'minimoons', which are small asteroids that are affected by Earth's gravitational pull and orbit the planet, but for a much shorter timeframe.

These minimoon are often only a few feet across, and each tends to do a stint of around a year in orbit - before resuming their previous lives as asteroids.

Scientists hope to one day 'catch' a quasi-satellite which could offer a valuable sample of material largely unchanged since the dawn of the solar system 4.6 billion years ago.

In 2012, a team led by University of Hawaii at Manoa calculated the probability that at any given time Earth has more than one moon.

They used a supercomputer to simulate the passage of 10 million asteroids past Earth.

They concluded at anyone one time, there should be at least one asteroid with a diameter of at least one meter orbiting Earth.

Scientists hope to one day 'catch' a quasi-satellite which could offer a valuable sample of material largely unchanged since the dawn of the solar system 4.6 billion years ago. Pictured is an artists's impression of Earth rising above lunar horizon

Our planet has also had a number of 'minimoons'. These space rocks are often only a few feet across, and each tends to do a stint of around a year in orbit - before resuming their previous lives as asteroids