(covers information from several alternate timelines)
The Aeon was a 29th century Federation timeship operated by Starfleet. Classified as an Aeon-type timeship, it was capable of traveling through time via generation of temporal rifts. Captain Braxton was the commanding officer of the ship.
Encounter with Voyager
The Aeon was encountered by the USS Voyager in the year 2373 in the Delta Quadrant, when Braxton traveled back in time to destroy Voyager. Braxton explained that, in the 29th century, a powerful temporal explosion had destroyed all of Earth's solar system, and that debris from Voyager's hull had been found in the aftermath. Believing that Voyager was somehow responsible for the explosion, Braxton embarked on a mission to destroy Voyager in an attempt to prevent the explosion from happening. Successfully countering Braxton's attack, the Voyager crew destabilized the temporal rift, which pulled both ships in and sent them back to Earth, Voyager to 1996, and the Aeon to 1967. Crashing in the High Sierras, Braxton managed to execute an emergency beam-out, but was unable to locate the Aeon before it was found and taken by a camper named Henry Starling.
Over the next thirty years, Starling would utilize his primitive understanding of the timeship's technology to introduce new computer innovations to the public, constructing a corporate empire and initiating the computer revolution of the 20th century.
In 1996, the Voyager crew located Braxton, who had been living as a vagrant ever since crashing. Braxton informed Captain Janeway of his deduction that, if Starling were to use the timeship to travel to the 29th century without properly recalibrating the ship's temporal matrix, then that could have been the cause of the explosion. The crew of Voyager was able to prevent this future by destroying the Aeon with a manually-launched photon torpedo just before Starling entered the temporal rift, an act which had the effect of creating a new timeline in which the explosion never occurred. Moments after Starling's rift dissipated, Voyager encountered another temporal rift, created by Captain Braxton's counterpart from the new timeline, who had detected Voyager's anomalous presence in the 20th century and had traveled back in time in the Aeon to escort them back to their proper time and place. (VOY: "Future's End", "Future's End, Part II")