The 3D extravaganza starring Sam Worthington, Sigourney Weaver and Zoe Saldana is set on Pandora, a distant planet inhabited by the Na'vi a race of aliens with blue skin.

For the past few years the four planned follow-ups have simply been referred to as Avatar 2, Avatar 3, Avatar 4 and Avatar 5.

And details about the four sequels have been more elusive than the element Unobtanium!

This week however, BBC News has seen documentation regarding future Avatar plans which makes reference to four specific projects. Avatar: The Way of Water, Avatar: The Seed Bearer, Avatar: The Tulkun Rider and Avatar: The Quest for Eywa.

The Way of Water

James Cameron has said that future instalments of the film will explore the planet Pandora's oceans and in 2017, confirmed to Collider that "there's a tremendous amount of water work across Avatar 2 and 3"

Reunited: Looks like Rose jumped ship to join the Sea People

In an interview with Vanity Fair, Cameron also revealed that Kate Winslet, who he worked with on Titanic, was joining the Avatar series playing "a character who's part of the Sea People, the reef people."

Eywa in The Quest for Eywa appears to be a reference to the deity and goddess of the Na'vi people who inhabit Pandora.

Shortly after the first movie's release, Cameron said: "I don't want to call it Avatar 2" because the lead character was no longer an avatar by the end of the film.

However, it seems likely that 20th Century Fox, the studio behind the series, will be keen to keep Avatar in the titles as it's such a recognisable name.

The documents refer to the projects both with and without Avatar as part of the title.

Last week, Sigourney Weaver, who stars as Dr Grace Augustine, told the Hollywood Reporter that "we just finished shooting 2 and 3" and that she was now preparing to be "busy doing Avatar 4 and 5".

The four Avatar sequels are due to be released in December 2020, December 2021, December 2024, and December 2025.