The unknown bright object flashing across the sky at Heathrow Airport. Youtube/AIRLIVE net

An extraordinary footage has captured a bright object flashing across the sky at London's Heathrow Airport, just before a passenger plane was about to land.

Aviation website Airlive shared the video suggesting that the object is a shooting star. Writing on the social media site, Airlive said: "Look at that amazing shooting star our cam just caught in the sky of Heathrow Airport!"

The video was soon shared widely on Facebook and Twitter, but some disagreed with the given description. A Twitter user Paul Mottershead said: "That was no shooting star. More like a large meteorite." Others described the sighting something 'awesome' and 'superb".

It is not yet known whether the mysterious object is space debris, a meteor, UFO, or something else.

A visiting fellow of the University of Southampton who specialises in studying space debris, Clemens Rumpf told Daily Mail: "My hunch is that this was a large meteor about one metre in diameter. These events occur harmlessly multiple times a year but can be spectacular when caught on camera."

Another explanation for it could be that the object was a piece of space debris falling to Earth. Reportedly, over 500,000 large pieces of man-made debris, or 'space junk', were tracked by Nasa and up to 150 million smaller untraceable objects are believed to be in orbit around the Earth.

So, that's quite a possible option. That being said, conspiracy theorists on the other hand recently said that they believe the astronauts are hiding some information after footage from the international space station showed a fiery object racing towards the Earth's atmosphere. The footage was taken by Italian astronaut Paolo Nespoli.

"The ISS crew member has said he believes that the object could be space debris," Daily Mail reported. However, both the space agency and alien enthusiasts have rejected the given explanation.