This ship is completely fictional, although the Horizon is also the name of the weapons platform used in "First Strike" of Stargate Atlantis. The Horizon-class battlecruiser was built with reverse-engineered Asgard technology from the Odyssey. Although the technology on the Horizon is nowhere near as advanced as the original technology installed on the Odyssey by the Asgard, she is still a formidable warship. The humans cant completely duplicate the new Asgard technology from the Odyssey, and with the Asgard now extinct, they've had problems trying to copy the technology. The Odyssey still has the advantage over the Horizon in that the technology was installed by the Asgard themselves, and the Odyssey has a ZPM. The Horizon is equipped with several prototype devices such as an anti-prior device that would be used to disable the prior controlling an Ori battlecruiser. Another experimental weapon is a phase-shift generator, that could possibly shift the Horizon out of phase to avoid an enemy attack. The Horizon has a bomb bay just like the Apollo for launching big bombs.
If you have seen the episode "Unending" you would know that the Asgard are no longer around. Maybe It hasn't aired in the US yet but I have pieced together clips from Google and other sources, the Asgard are extinct. As much as I love the Asgard, they are gone.
