Therefore, its known narrative elements are not a part of the Doctor Who universe as we, on this Wiki, choose to define it. It may have been the basis for a similar story in another medium, however — and that story may indeed be valid.
Figure of Eight was an unproduced Bernice Summerfield audio story written by Iain McLaughlin. At the recording of McLaughlin's The Eye of the Scorpion on 21 July 2001, Gary Russell invited him to pitch a Bernice Summerfield story.
The story had Benny being sent to Bartel, a planet with a schism between religion and science, by Braxiatel to observe the planet's regular transition from orbiting one sun to another. Moving in a figure of eight, Bartel is fertile and healthy when orbiting one star but cold and inhospitable whilst orbiting the other, which is dying.
McLaughlin completed his first draft in September 2001 and, after going through it in detail with Claire Bartlett, sent it to Russell. It was listed on the Big Finish website as story 3.4 but was later removed, Russell having decided that it was too similar to Professor Bernice Summerfield and the Dance of the Dead. (REF: Bernice Summerfield: The Inside Story)