A Nova Javelin is a powerful explosive-projectile weapon used by the Kryptonian Defense Force, capable of yielding as much or more damage than thermonuclear warheads.
Nova Javelins apparently were invented during the Age of Wars and were used by Jax-Ur to devastating effect; apparently, three of them were enough to blow up Krypton's third moon.
After the Age of Wars, the Kryptonian Defense Force adopted them, and over countless millennia they were modified and refined to maximize efficience and equipped with countless safeguards to contain the damage to an area as small as possible, although they were considered mostly as a last resort.
In the present time, Superman used a Nova Javelin to destroy Noram's entire Orca fleet. The impact caused a tremor so strong that it was felt in the Middle Eastern, and caused a lot of unrest on the U.S. Senate, particularily with Senator Robert Kelly.
Later, in the aftermath of the conflict against the Kree, Skrulls and Shi'ar, General Zod threatened to deploy a Nova Javelin from Sentrius to destroy the remaining of the main Skrull fleet, thus rendering their empire completely defenseless unless they accepted the terms and signed the treaty to end hostilities once and for all. Later, Zod had Sentrius launch a Nova Javelin at the North Korean peninsula, after they were attacked by a salvo of thermonuclear missiles from a military North Korean base, taking this as his chance to retalliate and conquer Earth. Unable to get Sentrius to call off the attack, Superman tried to stop the Nova Javelin himself, but Zod prevented him from doing so, and the impact destroyed a huge part of the country, killing millions in the process.
Background information Edit
In the novel The Last Days of Krypton, the Nova Javelin was the weapon used by Jax-Ur, that destroyed Krypton's moon Koron, and it involved alien technology, although this was never discovered for many years.