Astronomer Mr Cox has repeatedly openly ridiculed the Nibiru myth on Twitter, and insists it is nothing but a hoax.

However, according to conspiracy theorists, Mr Cox might secretly believe the myth, and tried to warn us about it by "showing Nibiru on camera in the sky" more than once during an episode of the hit BBC2 show.

A YouTube video by channel Christo Central says Mr Cox showed "two suns in the sky" on two occasions during an episode about comets.

The "Nibiru sightings" came after Mr Cox detailed how comets had brought water to Earth to create our oceans, and how they had wiped out the dinosaurs, with an extension-level impact.

The internet has been awash with barmy theories claiming the Nibiru or Planet X system is heading towards Earth, and will trigger a global apocalypse from Sunday, November 19.

So-called Nibiru truthers say NASA is at the heart of a global elite conspiracy to hide the truth from the general population while they seek refuge in secret underground bunkers.

The Nibiru myth emerged in 1976, when writer Zecharia Sitchin claimed two ancient Middle Eastern cultures, the Babylonians and Sumerians, told of a giant planet dubbed Nibiru which orbited the Sun.

And the Nibiru or Planet X theory claims a mini solar system consisting of a sun, planets and moons is lurking in space on the edge of our system with a huge 3,600 miles orbit of the sun.

They say the planet will cause the poles to switch, sparking great earthquakes and volcanic eruptions, while comets will rain down on Earth.

Despite Mr Cox making no mention of Nibiru or Planet X in the video, Christ Central claims he "shows Nibiru in the sky" after speaking about a "deep impact” of the dinosaur killer comet.

They claim this was a cryptic sign to viewers about the threat of Nibiru, from Mr Cox, without him actually publicly doing so.

Many Nibiru theorists claim it will drag great comets in its wake, many of which will rain down on Earth during the apocalypse.

When Mr Cox refers to our sun in the episode as "our nearest star" subtitles appear on the Youtube video saying: "OK, which star is he referring to? Because he is about to reveal TWO SUNS IN THE SKY!"

A promotional blurb for the video states that the video was initially banned, saying: "This is a shortened version of the video that was BANNED WORLD WIDE a week ago. In it Brian Cox may be hinting at a coming cataclysm on the Earth?"

The video then shows another view of the sun, which it claims includes two objects in the sky.

Subtitles state: "See two suns in the trees? Pretty hard to fake that."

A few viewers appeared to be convinced by the video, but many branded it fake or just nonsense.

The majority verdict was that it was just a reflection of the sun through the train window or a lens flare when light refracts inside the lens, creating two images of a light source.

Lori Noneya posted on YouTube: "This is simply a reflection off the window. 

"Go frame by frame when the boxcar/train passes, you actually see the 'second sun' on the side of the boxcar."

Another poster called The Real Mr Pink added: "I believe those are most likely lens flares. 

"What we are most likely seeing in this footage is ghosting or ghost flares. Its probably caused by multiple lenses."

So another Nibiru conspiracy theory appears to have bitten the dust.

NASA has repeatedly said Nibiru does not exist. 

Dr David Morrison, a scientist with the space agency, said: "There is no credible evidence whatever for the existence of Nibiru. 

“There are no pictures, no tracking, no astronomical observations.

"I can quite specifically say how we know Planet X or Nibiru does not exist and does not threaten Earth.

“Firstly, if there was a planet headed into the inner solar system that was going to come close to the Earth, it would already be inside the orbit of Mars, it would be bright, it would be easily visible to the naked eye - if it was up there it would be easy to see it, all of us could see it." 

Dr Cox has also repeatedly insisted Planet X does not exist.

He once tweeted: "If anyone else asks me about 'Nibiru' the imaginary bulls**t planet I will slap them around their irrational heads with Newton's Principia."