not sure if Dan changed the conditions of the task when he added more planets to the data base or if this is a bug
but aperently the planets needed for the artifact no longer need to be "scanned in the last 5 minutes."
I was able to finish this one, using basickly any "old" VL+ enemy planet I had on scanner, including planets shared by legion members and Old planets I had scaned more then 1 month ago (and some of them a lot older then that)