M87

M87 was a galaxy.

History
Circa 4,999,999,740 AD one of its constituent planets, New Savannah, joined the New Earth Empire, which was presumably set up before the aforementioned date. (COMIC: Agent Provocateur)

By 5,000,000,023 AD, humanity was fully established (with a population of at least ten million) on the planet New Earth after the original had been destroyed 23 years earlier. The planet had a similar orbit, atmosphere, and size to the original Earth. (TV: New Earth)

A population of devolved Macra were discovered living deep beneath New New York by Martha Jones and the Tenth Doctor while they were on New Earth. (TV: Gridlock)

M87