Upon their return to the ship, she and the Doctor discover the plan of Max Capricorn (George Costigan) to destroy the Titanic, its passengers and the nearby people of Earth with his villainous angelic robots, the Host.

As they attempt to save the ship, Astrid grows increasingly fond of the Doctor, kissing him as part of what she assures is an "old tradition" on Sto.

Astrid reappears spectral and bewildered, as the Doctor gives her a goodbye kiss before freeing her sentient atoms (described as "stardust") to roam space as energy.

The Doctor later uses a 'Once More With Feeling' device to revisit memories of losing friends, including Astrid's death, to generate enough personal grief that the Shroud releases its victims and latches on to him.

In August 2007, screenwriter and executive producer Russell T Davies announced that Astrid Peth would be the next companion, following the positive reception towards Martha Jones, (played by Freema Agyeman).

Later in his book A Writer's Tale Davies discussed with co-author Benjamin Cook how he had originally named the character "Peth" in a treatment but it bugged him, he later renamed her to "Astrid" giving the reason that it "...sounds more spacey, more like a futuristing [sic] Doctor's companion".

[5] Tenth Doctor actor David Tennant interviewed Minogue about her role as Astrid Peth on BBC Radio 2 in X-Amining Kylie first broadcast on 27 November 2007.

[29] Conversely, Paddy Shennan of the Liverpool Echo accused the makers of cynically including shots of Minogue's cleavage and legs.

[30] Tim Teeman of the Times Online described Astrid as "gutsy", but commented on Minogue's "older" appearance and likened her "breathy delivery" to her performance as Charlene Mitchell in Neighbours.

[31] In 2012, Will Salmon of SFX named Astrid's demise as one of the five worst companion departures, writing that her death circumstance was "a bit daft" and her starlight farewell was a "laughably mawkish scene".

[32] Billie Piper, who portrayed former companion Rose Tyler, commented that it was a "great idea" to cast Minogue, and was disappointed to miss meeting and befriending her on the set of Doctor Who as Tennant had done.