I think its a good idea, though it shouldn't be found randomly. Otherwise a player could find it on his first asteroid and not let the other team have any real chance to take it.
It could be something that remains hidden until a set length of game time has occurred and then found by the normal research planet function. If you have already searched all of your planets before the timer goes off, then it will just appear on whatever planet it was set on when the timer goes off.
As a sidenote, I would love additional artifacts, I think they really can add some fun variety to the game. Here are a few I've thought of:
Gravity Field Nullifier: Phase jump from 15% deeper in Gravity Wells. All Ships with Jump Drives.
Density Matrix Armor: Increase armor by 2. All Ships & Structures with Armor.
Phased Particle Arrays: Increase Shield Mitigation by 5% and increase Phase Missile Block by 15%. All Ships & Structures with Shields.
Matter Terra-former: Increase maximum population by 10%. All Colonized Planets
Planetary Defense Drones: Attacks Bombarding Ships with Drones. All Colonized Planets
Tactical Super Computer: Reduce enemy accuracy 20% against SC. All Owned SC.
Obviously the actual numbers could be played around with but these are just some fun ideas.