Earth Death

Earth Death, also known as the end of the world, was the name given to the event in the year 5.5/Apple/26, better known as 5,000,000,000, in which the planet Earth was ultimately destroyed, having been engulfed by the Sun as it became a red giant. It was attended by guests who were, as the Ninth Doctor put it, worth "zillions".

At Platform One, Earth Death was scheduled for "15 39". The Doctor likened the planet's destruction to the fall of Gallifrey, having believed his homeworld to have "burned" at the end of the Time War. (TV: The End of the World)

Prelude
As the Sun expanded, the Earth was completely vacated by its former inhabitants, namely humanity, who by the year 5,000,000,000 were said to have "touched every star in the sky". The mother and father of the Lady Cassandra O'Brien.Δ17 were said to be the last to be buried in the Earth's soil.

By this point, the now uninhabited planet was the property of the National Trust, who kept it preserved by using gravity satellites to hold back the Sun while reversing the shifting continents to a classic Earth formation. Ultimately, however, the Trust ran out of money to the Earth preserved and so, as the Ninth Doctor put it, "nature took over". (TV: The End of the World)

The Event
The coming destruction of the Earth, named "Earth Death", was designated as an "artistic event" to be witnessed aboard the observation deck Platform One, a space station owned and placed in orbit of Earth by the Corporation and staffed by Crespallions, who were managed by a Steward. The main sponsor for the event was the Face of Boe of the Silver Devastation, who invited several guests to witness the event. As the Ninth Doctor observed, these guests were mostly extra-terrestrials or multiforms and composed of "the great and the good" or rather "the rich", being worth "zillions".

The guests in attendance, transported via shuttles, were the Earth tree-descended Forest of Cheem, represented by Jabe, Lute and Coffa, the Moxx of Balhoon from the solicitors Jolco and Jolco, the Adherents of the Repeated Meme from Financial Family Seven, Hyposlip Travel System inventors the brothers Hop Pyleen, Cal "Spark Plug" MacNannovich, Mr and Mrs Pakoo, the Ambassadors from the City State of Binding Light, and a pair of Wicker Men. Lastly, a special guest called forth in memory of the dying world was the Lady Cassandra O'Brien.Δ17, the so-called "last human", ever attended by two surgeons; the last "pure" human, Cassandra regarded the others of this time as "mongrels". In addition, the Doctor's TARDIS landed aboard the station as the Doctor took Rose Tyler, a human from 2005, on her first trip; using his psychic paper, the Doctor passed himself off to the steward as a guest with Rose as his "plus one".

Cassandra used metal spider robots to sabotage Platform One's computer systems and the Adherents of the Repeated Meme, who were actually android constructs, to direct attention away from herself as the spiders sabotaged the platform's sun filter. Her original intent was to create the appearance of a hostage situation and collect compensation (with it not being apparent she was the hostage taker) to fund her cosmetic surgical procedures.

When that plan was exposed by the Doctor, she teleported off the station, leaving it to be consumed, eliminating both the evidence and allowing the shares she held in the guests' rival companies to triple. Among those killed by the heat were the steward, Raffalo, a Crespallion worker, the Moxx of Balhoon, and Jabe, who gave her life to assist the Doctor. Ultimately, thanks to Jabe's sacrifice, the Doctor reset Platform One's systems just before the Earth exploded, saving the station. (TV: The End of the World) At the same time as the sun swallowed the Earth, a group of Daleks from the Second Dalek War were tricked into flying into the sun, having been sent there from the Cathedral of Contemplation by the Tenth Doctor and the Fourth Doctor. (AUDIO: Out of Time)

Aboard Platform One, the Doctor reversed the teleportation feed, bringing Cassandra back. In the heat, and without her assistants to moisturise her, Cassandra's skin dried, stretched and exploded, apparently killing her, although her brain was not destroyed. (TV: The End of the World)

Separately, the Twelfth Doctor took a Hyperion fusion web which was placed around the sun in 2015, connected it to his TARDIS, and transported it to the year 5000000000 where it would be destroyed as the sun expanded. (COMIC: The Hyperion Empire)

Aftermath
Following the incident at Platform One, Cassandra was retrieved by Chip, a force-grown clone and her servant, who salvaged her "pretty blue eyes" from the bin before restoring Cassandra using an extra piece of skin taken from her discarded body. (TV: New Earth)

According to the Tenth Doctor, a "big revival movement" motivated by nostalgia rose as "soon as the Earth burn[t] up", leading humanity to seek a new planet, which they found in the galaxy M87, located 50,000 light-years from the old Earth; being the same size as the old Earth with the same air and orbit, this plant was named New Earth. In light of its discovery, a call was sent out, with humans moving in en masse. The planet was visited by the Doctor and Rose in the year 5,000,000,023. (TV: New Earth, Gridlock)

The Moxx of Balhoon was survived by his brother, the Elth of Balhoon, who sought revenge for his death. Believing that the survivors of the incident had not tried to help the Moxx and had abandoned him to die, and decided to kidnap them, using his "bioslaves" to take his revenge. The Doctor and Rose discovered his plan and rescued his prisoners. The Doctor convinced the Elth that they had done all they could to save him but it was too late. The prisoners not only forgave the Elth for kidnapping them, but they offered to help him. (COMIC: Reunion of Fear)

Behind the scenes

 * In The Trip of a Lifetime, the Ninth Doctor tells the audience that they will see "the day the Earth died in a ball of flame".
 * In the video game NOTVALID: K9: Deja Who, it is K9 who thwarts Cassandra's Earth Death plot instead of the Ninth Doctor and Rose Tyler. To that end, he tracks down and deactivates the metal spiders before navigating through Platform One's fans to switch on the shield against the Sun, leaving Cassandra to succumb to the heat.