A dying planet at the fringe of Mutter's Spiral was supposed to become a nova in the 22nd century. However, the Zircon destroyed it in 1974 at their Emperor's command to create a galactic cyclone that would wipe out the people of Earth as a poison cloud.
According to one account, the Third Doctor had taken Sarah Jane Smith in the TARDIS to look at the dying planet from less than a light year away before having to retreat. According to another, it was the Fourth Doctor and Joan Brown. (COMIC: Doomcloud)