ROBBIE WILLIAMS’ obsession with extra-terrestrials has just jumped to lightspeed.

The beardy pop nob has been spending his free time – which is about 18 hours, seven days a week – visiting observatories in the Arizona desert.

Rob has been peering through telescopes looking into space for signs of life on other planets.

Telescopes … Robbie’s got his eye on one

Surely writing a new album is more important than staring at the heavens like eccentric, xylophone-playing Sky At Night TV host PATRICK MOORE?

Robbie has been visiting the National Optical Astronomy Observatories in Tucson, Arizona, pictured above, to do his star gazing.

He has become so obsessed with his new hobby he is planning to buy an observatory – a mere snip at £2.5million.

More money than sense, eh?

A source said: “Some of Robbie’s acquaintances in LA have been having a chuckle at his expense.

“He is leading a bizarre existence at the moment – vanishing into the desert to look at stars in far-flung galaxies. He is dead set on buying himself his own observatory in the desert. He is hooked on all things from outer space.”

I always thought Robbie was wired to the moon. The singer based his 2006 Close Encounters concert tour on UFOs.

And in the last few months he has got friendly with crackpot ex-sports presenter DAVID ICKE, who believes key world leaders, including GEORGE W BUSH and TONY BLAIR are reptilian aliens disguised as humans.

Robbie also appeared on radio last week to talk about three dramatic sightings he has had of UFOs in LA – and his desire to hang up his mic to study aliens after his ET experiences.

Robbie said: “I’m stopping being a pop star. I’m going to be a ufologist.”

He says he also believes the cult of Scientology “exists” and thinks ghosts “are other worlds”.

He added: “I was lying on my sun lounger outside at night. Above me was a square thing that passed over my head silently and shot off.”