This week, in an "out of this world" show, Graham Norton meets award-winning actress and star of Alien and Avatar, Sigourney Weaver, and the master of the universe himself, Professor Brian Cox. Sandi Toksvig and top-selling US band Sugarland complete the stellar line-up.

On the extraordinary success of being in the biggest sci-fi movies of all time, Sigourney says: "I found sci-fi a little cold and cerebral and was more interested in action, but I love it now. I got lucky – I've only made five science fiction films but they all turned out to be wonderful."

She says of her new film, Paul: "It's a love letter to sci-fi fans. I jumped at the chance to be in it. To find a comedy that is also pays homage to sci-fi is a dream come true."

And on a possible Avatar sequel, Sigourney reveals: "There may be more than one."

On the uniqueness of science fiction fans and whether she is mobbed, she says: "They are very passionate and I love the conventions. I have put on a Batman mask so I can cruise through the convention. It was marvellous and I hated to leave."

Talking about his own love of sci-fi, Brian Cox says: "I was born in 1968 at the tail end of Apollo, science fiction merged in and I couldn't tell the difference. Star Wars came along and then Alien, which made a huge impact on me. It was one of the first films I saw on the big screen and it's my favourite science fiction film to this day."

He assures Sigourney: "You didn't put me off going into space."

Sandi Toksvig tells her own amazing Apollo story: "I was 11 years old and in mission control in Houston holding the hand of Neil Armstrong's secretary."

She explains: "I was there with my father, who was covering the event for Danish TV, when I met this woman who told me she was nervous because she knew the man that was going to land on the moon. So we stood and held hands as he stepped out on to the moon."

On his new series, Wonders Of The Universe, Brian Cox says: "It's the story of the universe from the Big Bang, how the chemical elements got here, its progress and what its future might be," before revealing, "This is really miserable, but we think the universe is going to end in a heat death when all the stars have gone and black holes have melted away."

Sigourney and Sandi re-enact the most famous scene from Alien, and Brian, recently named one of the sexiest men in the world, takes part in a "blind date" with geeky members of the audience.

Sugarland perform Stuck Like Glue live in the studio.

And finally, Graham pulls the lever on foolhardy members of the audience brave enough to sit in the red chair.

The Graham Norton Show, Friday 11 February at 10.35pm on BBC One.